AWUS01 KWNH 170303
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-170830-

Mesoscale Precipitation Discussion 1176
NWS Weather Prediction Center College Park MD
1002 PM EST Mon Dec 16 2024

Areas affected...Southern Arkansas...Northwest Mississippi..Adj
portionsOK, TX, LA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 170300Z - 170830Z

SUMMARY...The potential for continued back-building of weakening
but training showers may present a low-end scattered incident or
two of flash flooding through the overnight hours.

DISCUSSION...GOES-E WV suite denotes an elongated trough/stream
intersection extending from northeast Texas across the Delta
Region of the MS River toward the southern Ohio Valley toward the
tail end of the more amplified exiting flow across the Lower Great
Lakes. GOES-AMVs confirm RAP analysis of this intersection
extends the length of the broad right entrance to the 70-90kt 3H
jet across the TN/OH valley. A small inflection/wave is highly
divergent across NE TX providing the enhanced ascent pattern noted
with strong cirrus filaments along the northern edge of the
convective clusters across NE TX, AR into N MS/SW TN. The deep
unidirectional flow extends back to central TX, where moisture is
generally confluent before veering into solid isentropic ascent
toward the upper level jet entrance. As such, CIRA LPW and RAP
analysis show an enhanced pool of moisture starting to near 1.5"
with the vast majority below 850mb.

Surface analysis shows defined sagging cold front across AR, that
is starting to sharpen, with warm sector southerly flow providing
weak but sufficient surface convergence from 5-10kts. Strong
convection with some weak QLCS features generally training along
the boundary/deep layer moisture interface are fed upstream by
pool of 1000-1250 J/kg of MUCAPE before diminishing rapidly toward
N MS. Rates of 1.5-1.7"/hr are probable given moisture/unstable
air and with training profiles may allow for streaks of 2-3"
totals, though eastward along the line will see enhanced
southeastward propagation. While soil conditions are fairly
dry/generally recepible; they are starting to go a bit dormant and
rates may be sufficient for localized pooling/enchained run-off.=20
As such flash flooding is considered possible.=20=20

While upstream convection appears to becoming a bit more fractured
due to slightly weaker flow, the upper-level divergence/outflow
channel is suggestive/supportive of back-building/isentropic
ascent. Additionally, this mid-level wave is supporting some
shortwave ridging across SW to south-central AR and backing
propagation vectors to be be more northward allowing for greater
potential for training cells through the next 4-5 hours. Hi-Res
CAMs are inconsistent in the evolution overall convective activity/coverage...given the weakened upstream convergence, but
ones that do have stronger convergence do depict a higher
potential for training/back-building signal near areas that have
already received the higher rainfall resulting in initial flash
flooding warning. Confidence is high contingent on the evolution
and so the risk for continued flash flooding across Texarkana
toward the central LA/AR border is also considered possible
through 09z (as signals further diminish through the entire hi-res
CAM suite).

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4JL0cz_VHm3h9p4tVjTc76TK83nt1BoJs5dsXu1ORbV9cyx5DbBbMIFhfgvCHAe5i5sJ= CN4gz7US5su4YfGLjs8bzDY$ for graphic product...

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 34649054 34488968 33928946 33409022 33069166=20
32919259 32909333 32849406 33109473 33359479=20
33799453 33989415 34199346 34409209=20

=3D =3D =3D
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AWUS01 KWNH 172204
FFGMPD
ORZ000-WAZ000-181000-

Mesoscale Precipitation Discussion 1177
NWS Weather Prediction Center College Park MD
503 PM EST Tue Dec 17 2024

Areas affected...western WA into northwestern OR

Concerning...Heavy rainfall

Valid 172202Z - 181000Z

SUMMARY...Areas of heavy rainfall will continue to affect western
WA into northwestern OR through tonight. While high rainfall rates
will not not be constant over the next 6-12 hours, rates will
occasionally surpass 0.5 in/hr and locally approach 1 in/hr into
the favored terrain leading to an additional 2-5 inches of rain
through Wednesday morning.

DISCUSSION...GOES West water vapor imagery at 21Z showed a
vorticity max embedded within a broader mid-upper level trough
axis near 41N 141W, tracking toward the east and preceded by a
130-150 kt upper level jet. A cold front was analyzed at the
surface out ahead of the upper trough with a surface wave near 42N
135W. An atmospheric river was noted with peak PWAT values of 1.2
to 1.3 inches on CIRA Advected TPW imagery and RAP analysis data
ahead of the cold front to the west of WA/OR. PWAT values along
the coast, near the mouth of the Columbia River, were just below
1.2 inches via GPS data, but when combined with southwesterly 850
mb winds of 40-50 kt, IVT values were estimated to be near 700
kg/m/s along the southern WA/northern OR coast. Downstream
rainfall rates into the northern OR Coastal Ranges have already
been observed in the 0.5 to near 1.0 in/hr range from earlier
today, but radar/satellite imagery indicated the heaviest rain was
shifting north into western WA.

Water vapor imagery does not suggest the base of the upper trough
is amplifying any more to the south and may even be beginning to
lift slightly north. A general E to ENE motion to the upper trough
is forecast by RAP guidance through the overnight which will
continue to translate the greatest magnitude of IVT values
northward across western WA, with the peak axis focusing primarily
into Vancouver Island just after 00Z, perhaps clipping far
northwestern Clallam County in WA. Peak rainfall rates along the
WA Coastal Ranges into the Olympics within the northward shifting
IVT axis should reach into the 0.5 to 0.8 in/hr range, perhaps
isolated values near 1.0 in/hr. A temporary lull in heavy rain is
expected for much of the Pacific Northwest just after 00Z followed
by another surge as the upper trough and surface cold front
approach overnight. From roughly 06Z onward, IVT values are
forecast to surge to near 1000 kg/m/s along the WA/OR coast via
recent RAP guidance, but only last for an hour or two at that
magnitude. The overnight surge is likely to produce rainfall rates
in the 0.5 to 0.8 inch range with localized values near or in
excess of 1.0 in/hr.

Additional rainfall totals of 2-4 inches are likely to occur
through 09Z for the WA Coastal Ranges into northwestern OR, along
with the upslope regions of the WA Cascades. Isolated totals in
excess of 5 inches cannot be ruled out, especially in any favored
southwest facing slopes of the Olympics where the duration of
higher rainfall rates is expected to be the longest. Gauges showed
24 hour totals of 1-2 inches for the Coastal Ranges and Cascades
so far, with localized maxima near 3 inches. Earlier collaboration
with the National Water Center and NWM output suggests flooding
should be isolated at best, partially due to dry antecedent
conditions, but 48 hour rainfall totals of 5-7 inches through
Wednesday morning will likely support notable rises on area
creeks/streams.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-E06sBTiKv_1XE9fjB-Sa5EcS8WulePp0i71Bzc_2R7jrYf7wCg9heGD1yHABLvMe-a7= 6QL8Ggj5rYHY1DZKV4_0uSQ$ for graphic product...

ATTN...WFO...OTX...PDT...PQR...SEW...

ATTN...RFC...NWRFC...NWC...

LAT...LON 49102238 49072164 48862117 48662101 48372094=20
48102088 47782096 47562096 47322103 47122107=20
46952103 46782107 46562129 46332135 46172137=20
45982159 45782159 45592169 45472197 45512216=20
45702243 45852246 46072267 46182270 46422248=20
46632258 46742255 46872228 46962223 47042238=20
47012275 46822305 46672311 46502308 46332320=20
46272340 46112344 45962345 45672333 45552337=20
45382341 45282347 45172354 44982347 44792356=20
44722384 44982433 45492455 46732462 48242509=20
48442453 48282397 48302321 48622290 48872289=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 172250
FFGMPD
FLZ000-180400-

Mesoscale Precipitation Discussion 1178
NWS Weather Prediction Center College Park MD
550 PM EST Tue Dec 17 2024

Areas affected...east coast of FL

Concerning...Heavy rainfall...Flash flooding possible

Valid 172248Z - 180400Z

SUMMARY...Localized flash/urban flooding will be possible along
the eastern FL Peninsula over the next few hours. Slow cell
movement and/or training will be capable of 1 to 3 in/hr rainfall
rates which may generate isolated excess runoff within the urban
corridor.

DISCUSSION...Radar imagery from KMLB and infrared satellite
imagery through 2230Z showed scattered thunderstorms occurring
along the east coast of FL between Cape Canaveral and Port Saint
Lucie, streaming in from the east following the mean low to
mid-level easterly flow between 10-20 kt. Surface dewpoints in the
lower 70s have contributed to anomalous mid-December moisture with
precipitable water values between 1.5 and 1.8 inches (90th
percentile) with 1500-2000 J/kg MLCAPE observed on the 22Z SPC
mesoanalysis.

Cells were located just north of a weak mid-upper level vorticity
max observed on water vapor imagery over south-central FL, along a
persistent west-east convergence axis seen in fading visible
imagery offshore of the east coast. Mean easterly winds in the low
to mid-levels have supported repeating cells with short-term
training, with observed rainfall rates of 1-2 in/hr near Vero
Beach. While recent cloud top cooling on satellite imagery has
appeared to migrate generally just offshore, redevelopment and
westward translation of heavy rain looks to continue a short-term
urban/flash flood threat from southern Brevard County into St.
Lucie County along the coast where an additional 2-4 inches will
be possible on a highly localized basis through ~01Z.

Indications are that these cells will weaken after 00Z as boundary
layer stabilization occurs with nocturnal cooling, with cells
shifting more offshore or perhaps dissipating. While the HRRR
hasn't been doing well with the ongoing placement of cells, there
are indications in recent HRRR guidance that the activity could
refocus a bit farther south sometime in the 00-03Z time frame.
Similar potential for slow movement and/or training will exist is
development does get going farther south later tonight. Any areas
of flash flooding are expected to remain localized with potential
for a quick 2-4 inches over the next few hours.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5Q_aGikNvzafCzBZkLacufk8V7gRB8rgpd-NiBBSPYDk2FeZhieib_YkAuz--L98hVCe= yJGOyht5Bs8lDtVQwfvAzcU$ for graphic product...

ATTN...WFO...MFL...MLB...

ATTN...RFC...SERFC...NWC...

LAT...LON 28308046 27768008 26657985 26118002 26178029=20
26258043 26628045 27058049 27558065 28018077=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 180351
FFGMPD
MOZ000-ARZ000-TXZ000-OKZ000-180920-

Mesoscale Precipitation Discussion 1179
NWS Weather Prediction Center College Park MD
1050 PM EST Tue Dec 17 2024

Areas affected...Southeast OK...South-central MO...Far Northeast TX...Arkansas...

Concerning...Heavy rainfall...Flash flooding possible

Valid 180350Z - 180920Z

SUMMARY...Another round of elevated occasionally training
showers/thunderstorms with capability of 1.5"/hr and localized
totals of 2-3". Intersection with recently saturated increasingly
dormant soil conditions may result in increased localized run-off
and low-end flash flooding potential overnight.

DISCUSSION...03z surface analysis depicts an older polar boundary
draped across the Red River Valley, S Arkansas into the TN River
Valley. CIRA sfc to 850 LPW shows return moisture from the western
Gulf of Mexico streamed northward across central TX, then angling
northwest across much of AR while ascending across/above the
boundary into the 850-700mb layer. Total PWat values are in the
1.25 range, but sharpening upper-level polar trough across the
Central High Plains is increasing flow through the layers into the
30-40kt range through 700mb while sharpening the isentropic
boundary as the northern stream cold front presses further south
and east over the next few hours. Modest, mid-level drying and
lingering steeper lapse rates along with the near surface
moisture/heating is providing solid MUCAPE over the boundary with
values of 1500-2000 J/kg spreading across SE OK. Additionally to
the strengthening low level convergence/isentropic ascent; the
right entrance of the 100 kt jet is dropping southeast providing
solid divergence and evacuation to developing elevated convection
(while also moving into broadly diffluent region across S MO/AR
into the MS Valley).

Current GOES-E 10.3um and regional RADAR mosaic depict numerous
narrow core cells breaking out in two SW to NE orientated bands
across E OK and north-central AR. Coverage will increase and
updrafts will broaden to support 1.25-1.5"/hr rates occasionally
increasing to 2"/hr randomly and widely scattered in nature. Deep
layer flow while not ideally unidirectional, will support cross
track/repeating particularly over the first 2-4 hours before the
stronger flow/height-falls aloft increase forward cell motions and
increase southeastward cell propagation. This should allow for a
few scattered incidents of 2-3" totals across E OK/W AR and
perhaps even further downstream; which is likely to align with
areas that missed out on the moderate/heavy rainfall a few days
ago; but FFG values of 1.5"/hr and 2-3"/3hrs are well within
range. Still there are some overlaps along the edges of
south-central MO and eventually SW AR to south-central AR...that
may be more susceptible given soil saturation values per NASA
SPoRT at or above 65-70% in the 0-40cm layer. Also considered,
flash flooding is possible, but given rates and totals are at the thresholds...any flash flooding is likely to be on the lower end
and scattered in nature with highest potential in urban locales.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9k0OktekT6-4MAB-s6CmNq1zWrJWc0ukpHtcoOWW2wcxIkYIgfPTxAYzKsNIDQVsEgyO= NeeMQe8udUjNq2_YpnhJcBs$ for graphic product...

ATTN...WFO...FWD...LZK...OUN...SGF...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 36789162 36309120 35499120 34769177 33929358=20
33409564 33519674 34139694 34849641 36019480=20
36739300=20

=3D =3D =3D
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AWUS01 KWNH 180630
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-181130-

Mesoscale Precipitation Discussion 1180
NWS Weather Prediction Center College Park MD
129 AM EST Wed Dec 18 2024

Areas affected...Southeast MO...Northeast AR...Southern
IL...Northwest TN...Western KY...

Concerning...Heavy rainfall...Flash flooding possible

Valid 180630Z - 181130Z

SUMMARY...Warm advective showers/thunderstorms likely to expand in coverage/intensity toward early morning. Training/repeating
across wet/dormant grounds with low FFG suggest spots of 2-3" may
result in localized flash flooding conditions.

DISCUSSION...06z Surface analysis shows southerly return flow
across MS and W AL northward into W TN has pressed the warm front
into SW KY with lower 60s and upper 50s Temps and Tds starting to
trickle in through the MS Valley. Aloft, CIRA LPW and VWP network
show and increasing moisture plume on 30-35kts of 850-700mb WAA
across AR into the Tri-Rivers area bringing overall deeper layer
moisture values over 1.25" with short-term totals likely to near
1.5" about 09z. The combining streams, low level WAA profile with
modest lapse rates aloft have seen a steady increase in CAPE with
500-1000 J/kg analyzed across SE MO/NE AR at this time also to
focus into a nice SW to NE plume of 1000 J/kg by 09zZ into S IL/W
KY. As such, regional RADAR and GOES-E SWIR show scattered
thunderstorms W KY/E TN with greater cooling towers across SE MO
into NE AR with some tops reaching -60 to -65C; under increasing
influence of right entrance ascent/evacuation aloft of 100kt 3H
jet over N MO/N IL.

Given the strength of flux and available moisture, cores can be
capable of intense short-term rates with hourly totals of
1.25-1.5" given progressive/faster cell motions. Orientation of
cell development to the mean flow along with the scattered
downstream development (and heavier cells across NW TN/SW KY
earlier this evening) will allow for repeating over grounds that
already have 0-40cm soil moisture ratios well above normal (95+
percentile) over 60%. Hourly FFG values only further decrease
from west to east with hourly values of 1.5"/hr and 2-2.5"/3hrs
reducing to 1" and 2-2.5", respectively across central KY/TN.=20=20

Toward 12z, overall low level profile will continue to align SW-NE
and increase LLJ strength into the 35-45kt range. This should
allow for the scattered cells to orient into a longer linear
convective line from NE to SW though eastward propagation will
increase reducing the potential for training...all considered
scattered incidents of flash flooding are possible through the
morning toward daybreak.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!40Ie6Zq5yf8uB3MWqhWVGlCzKo9snejZAtX0MOTAzCi4qiOLLicShXJEzclSO_LIt0TM= IH5zPZN3bVkbZs6gL20vIaE$ for graphic product...

ATTN...WFO...LMK...LZK...MEG...OHX...PAH...

ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC...

LAT...LON 38218612 37798561 37208571 36798642 36078824=20
35469063 36109101 36699093 37299000 37878855=20
38198741=20

=3D =3D =3D
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AWUS01 KWNH 180916
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-181400-

Mesoscale Precipitation Discussion 1181
NWS Weather Prediction Center College Park MD
415 AM EST Wed Dec 18 2024

Areas affected...Southern Arkansas...Adj SE OK/NE TX/N LA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 180915Z - 181400Z

SUMMARY...Flattening convective line shows potential for training
over the next few hours while crossing saturated soils from recent
heavy rainfall across southern AR.

DISCUSSION...Recent GOES-E 10.3um and regional RADAR trends
suggest upwind edge of best isentropic convergence across SE OK
has seen a recent uptick in convective development. WV suite
depicts the right entrance of a speed max in the cirrus across
central OK at this time. This is resulting a downstream shortwave
ridging and flattening of the 500-1000mb thickness ridge allowing
for a more eastward propagation of the convective line likely over
the next few hours. CAPE analysis fields suggest highest theta-E
axis is ideally oriented for the isentropic ascent along the Red
River Valley. Cooling tops below -65C suggests stronger updrafts
and deeper moisture flux/rainfall production. CIRA LPW places .6
to .75" sfc-850mb moisture with additional 850-700mb layer over
.3-.5" allowing for totals of 1.25" to 1.4"; given 30-35kts of
flow; flux convergence will support rates of 1.5-1.75" and given
the orientation may allow for 1-2 hours of training before the
core of height-falls across W OK/NW TX dig more and start to
accelerate the cold front south and eastward and reduce the best
ascent angle to the front from the LLJ. As such a streak or two
of 1.5-2.5" totals remain probable across Texarkana and southern
Arkansas.

Unfortunately, heavy rainfall last evening has reduced upper level
soil capacity across this area with NASA SPoRT 0-40cm saturation
ratios well above normal in the 65-75% range. So believe FFG
values may have likely recovered too fast and grounds may be more
susceptible to increased run-off and potential for localized flash
flooding. By no means will the rainfall totals be great enough
for sizable areal coverage and/or magnitude of flash flooding, but
the potential remains sufficient for an incident or two to occur
through mid-morning across S Arkansas.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8ImBU7gdw3rEfK9MDyfI6Z8EhZJG1sGH7v7E9YKCKFHrFJ-g4cmmyOqL0Ji0NIw6JTO0= tOWh3VyxLlWscqrydoWoCH8$ for graphic product...

ATTN...WFO...JAN...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 34969203 34799153 34209115 33829110 33209133=20
32859199 32859382 33179485 33789516 34319482=20
34629404 34939286=20

=3D =3D =3D
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AWUS01 KWNH 181100
FFGMPD
TNZ000-KYZ000-181600-

Mesoscale Precipitation Discussion 1182
NWS Weather Prediction Center College Park MD
600 AM EST Wed Dec 18 2024

Areas affected...Central Kentucky into Western Tennessee...

Concerning...Heavy rainfall...Flash flooding possible

Valid 181100Z - 181600Z

SUMMARY...Progressive convective line with embedded intense
downdrafts capable of 1-1.5"/hr and quick 1.5-2.5" totals across
low FFG values suggest widely scattered incident or two of flash
flooding remain possible through late morning.

DISCUSSION...RADAR mosaic and GOES-E 10.3um EIR show a progressive
convective line with slight uptick of vigor over the last hour or
so as the deep layer moisture flux/convergence aligns with
remaining instability axis across central KY back to SW TN. Core
of highest theta-E air remains across W TN with 500-1000 J/kg of
CAPE that decreases slowly northeastward into central KY. GOES-E
WV suite shows polar upper-level trough has made main push east
and southward out of the Plains toward the MS Valley. Broad
divergence along the right entrance to the downstream jet streak
through the Great Lakes continues to maintain solid large scale
ascent while maintaining strength of the the LLJ across Arkansas
into the TN River Valley. Surface moisture in the mid-50s,
combined with the strong moisture flux convergence along the
leading edge of the convective line will continue to support
intense sub-hourly rain-rates in the range of 1.5-1.75"/hr though
duration is likely to limit totals to 1-2" with perhaps up to an
additional .5" within the broadening moderate precipitation
shield.

The progressive nature should limit overall totals; however, the
line is moving into overall lower FFG values of 1-1.5"/hr and
1.5-2"/3hr which remain possible of being locally exceeded.=20
Overall coverage and magnitude of flash flooding is likely to be
limited on the low end of exceedance. However, the potential for
flash flooding will remain possible until about 15-18z when
instability is nearly fully exhausted and moving into a more
stable, lower temperature/moisture environment through the
Cumberland Plateau.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6Md3hLJdhA941mUTQUxMeabtvfSbT989k_pMKdrhV7sY6s-q7FvjZyQEIAl93dn1fJGc= uVyrtBADLr2uMtqlro30JKE$ for graphic product...

ATTN...WFO...JKL...LMK...MEG...OHX...PAH...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38218366 37728326 36728462 35918596 35478705=20
35168826 35198946 35638955 36428855 36958775=20
37918608 38188508=20

=3D =3D =3D
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AWUS01 KWNH 240212
FFGMPD
CAZ000-ORZ000-241410-

Mesoscale Precipitation Discussion 1183
NWS Weather Prediction Center College Park MD
911 PM EST Mon Dec 23 2024

Areas affected...Northern CA into Southwest OR

Concerning...Heavy rainfall...Flash flooding possible

Valid 240210Z - 241410Z

SUMMARY...An atmospheric river moving into northern CA and
southwest OR will bring an increase in rainfall coverage and
intensity tonight into early Tuesday. Rainfall rates locally as
high as 0.5" to 1" in an hour may result in some flood risk.

DISCUSSION...This is a fairly progressive system, which will limit
the magnitude of rainfall totals and flood risk. However this is
also a dynamic system with a strong upper jet and deep mid level
trough moving inland. These features will help enhance ascent and
also allow for some weak instability along the front supporting
low topped convective elements locally enhancing rainfall rates.
The 18z HREF neighborhood probabilities of exceeding 0.5" in an
hour increase and expand in coverage ~04z across southwest OR and
northwest CA and peak in the 60-90% range from 06z-12z, with the
higher probabilities shifting southward with time. There are even
some 1" an hour probabilities showing up, peaking ~40% in the King
Range between 06z and 08z. The last few runs of the HRRR also
shows peak hourly rain ~0.75-1" along a narrow band from the King
Range into far southwest OR between ~04z and 08z. These rates
decrease some as the low topped convective line moves inland away
from the slightly higher instability just offshore, but both HREF
probabilities and recent HRRR runs still support localized
rainfall exceeding 0.5" in an hour inland. Despite the progressive
nature of this system, the potential for these aforementioned
higher rates does introduce some risk of rock and land slides long
with minor flooding of urban and other flood prone areas.
Antecedent rainfall has resulted in above average soil saturation
and near to above average streamflows, making the flood risk a bit
higher than it otherwise would be for such an event.=20

Guidance also suggests we may see anther uptick in rainfall rates
around 12z over the northern Sacramento Valley and adjacent
foothills. A combination of enhanced low level convergence driven
by stronger southerly flow up the valley, and slightly higher=20=20
instability values over the valley by this time, supports this=20=20
uptick in rainfall rates potentially towards 1" in an hour. These
higher rates will likely be fast moving by this time, and so the=20
heaviest rain at any one location should not last more than an=20=20
hour or so. This will help limit impacts, although rates could be
high enough to still result in some localized flood concerns.
There is a chance rainfall rates between 0.5" and 1" in an hour
could move over the Park burn scar around 12z. Rainfall rates of
this magnitude could result in debris flows, so while confidence
in rates reaching these magnitudes remains low, observational
trends will need to be monitored closely late tonight into Tuesday
morning.

Chenard

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4eSVyvBEISJtm2Pp2s5Uusl5WFNV6pSi3sVPQ6FGzsRFy5CL5U2_IJSkY2yzAZpq4KuM= FkOxjEfRzT2GBGEDAt48HEw$ for graphic product...

ATTN...WFO...EKA...MFR...MTR...STO...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 42842444 42652390 42122329 41652327 41392245=20
41312189 40772164 40382141 40052118 39932108=20
39662122 39702164 40012206 39792264 39202259=20
38592274 38302316 38482348 38712368 38982389=20
39782438 40242463 41152454 42102450 42642462=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 241325
FFGMPD
CAZ000-242200-

Mesoscale Precipitation Discussion 1184
NWS Weather Prediction Center College Park MD
825 AM EST Tue Dec 24 2024

Areas affected...Eastern Central Valley & Lower Slopes of Sierra
Nevada of California...

Concerning...Heavy rainfall

Valid 241330Z - 242200Z

SUMMARY...Quick hitting AR is starting to weaken, but 1-1.25" of
upslope along lower slopes of central and southern Sierra Nevada
will continue to pose a heavy rainfall threat into the afternoon.

DISCUSSION...GOES-W WV suite shows the very strong cyclone that
spurred the strong moisture advection and strong winds with this
Atmospheric River has lifted north and is making landfall
along/north of Vancouver island into central BC. However, the
base of the longer wave trough remains off-shore and is pressing
eastward toward the central CA coast. Weak sub-tropical ridging
just NE of the right entrance of the polar jet (see upstream wedge
of mid to upper level strato-cu with west-east transverse banding
signture) well south, generally parallel to Cape Conception.=20=20
CIRA LPW shows a severing of the core of the AR plume about this
location as well; combine this with slowly deminishing winds and
the AR IVT values are and expected to continue to reduce over the
next 6-9 hours, with a continued bifurcation of the moisture plume
near surface and mid-levels broadening post-frontally. 13z
surface analysis depicts the cold front starting to push though
the southern portion of the northern Valley, though low level flow
remains backed across the northern Valley. Residual deep moisture
and steepening lapse rates will allow for increasing instability
and recent HRRR suggests a few lingering convective cores remain
possible across the Valley moving southeastward post-frontally and
intersecting the already saturated lower slopes of Tehama, Butte
and Yuba counties with potential of spotty .5-1" additional totals
to maintain ongoing flooding concerns in the area.

The main AR core along/ahead of the cold front had an excellent
broad, higher reflectivity core that resulted in .5-1"/hr rates
but that continues to weaken with the aforementioned reduction of
moisture and flux. Still, the leading edge will have solid
moisture and fairly orthogonal intersection with the lower slopes
of the central and southern Sierra Nevada Range with .75-1" total
PWat and 35 reducing to mid-20kt flow to allow for .5"/hr reducing
to .25"/hr rates for 1-3 hours resulting in quick .75-1.25"
totals. This may near the naturally lower FFG values (.5-.75"/hr
or .75-1"/3hr) of within the complex/steeper terrain with a very
low but non-zero risk of widely scattered exceedance; though the
probability does not rise to FF possible category and will
consider this a Heavy Rainfall discussion and likely last MPD for
this event as the front rapidly presses through the Sierra Nevada
after 21z.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5TIbpStOrameMt-4LqYaC6SYsiivdq3C1ktByVq2Je6Ylbz9ryj49UqPiLWrsfe4tuSL= AmPUffAoGofCkvl6d1KZZgc$ for graphic product...

ATTN...WFO...HNX...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 40842182 40332159 39872129 39402079 38882053=20
38312021 37771978 37311927 36931884 35961832=20
35551828 35161864 35101903 35451942 36021972=20
36652015 37312038 37812088 38452114 39162152=20
39702195 40092221 40392241 40692236=20

=3D =3D =3D
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AWUS01 KWNH 241404
FFGMPD
ARZ000-TXZ000-OKZ000-241930-

Mesoscale Precipitation Discussion 1185
NWS Weather Prediction Center College Park MD
904 AM EST Tue Dec 24 2024

Areas affected...North/Northeast Texas...Portions of SE OK & SW
AR...

Concerning...Heavy rainfall...Flash flooding possible

Valid 241405Z - 241930Z

SUMMARY...Increasing convective activity with potential of
1.5"+/hr rates with back-building and short-term training
potential may exceed FFG, especially near urban centers resulting
in possible localized flash flooding.

DISCUSSION...GOES-E 10.3um loop shows convection breaking out
along the frontal zone across North Texas into the Red River
Valley with steady increasing lightning detection within most
active cores, particularly along the upstream edge. Surface
analysis denotes a weak surface low near F02 with stationary front
meandering through the Red River with northern stream cold front
slowly dropping southwest across eastern portions of the Big
Country back through the Concho Valley; south of which, returning
Gulf moisture is starting to encroach with reinforcing shot of
enhanced theta-E with mid 60s Tds in the southern Triangle lifting
north as well. CIRA LPW shows a slug of detached mid-level
moisture from the Pacific stream pooled along the frontal boundary
in association with a weak shortwave over northeast OK. GOES-E WV
suite also denotes, core of northern stream upstream larger scale
wave is starting to dig across the Central High Plains;
effectively strengthening the low level flow to further enhanced
deep moisture convergence over the midday into afternoon hours.=20
This has resulted in a 500-1000mb thickness ridge over E TX that
is supporting a veered propagation vector field that will align
with deeper layer steering for at least a few hours across the Big
Country into Northeast Texas providing a solid potential for 1)
training of convection but 2) increasing upstream moisture
convergence and steepening lapse rates (with modest mid-level
drying from the southwest) to support increasing instability and
convergence for development/backbuilding.=20

In the short-term, the cells are converting modest instability
with MLCAPE increasing to about 500-1000 J/kg along the upwind
edge with downstream cells likely becoming a bit more elevated
with MUCAPE pool of 500 J/kg to maintain more scattered/isolated
cells into SW AR with time. Solid deep layer convergence and
total PWats of 1.25" (though bulk of .75"+ at sfc/850mb layer)
will allow for some intense rainfall production. RADAR estimates
of 1.5"/hr have already be observed with potential for additional
capacity if the training/repeating corridor saturates through
depth.

A balance of unidirectional SSW steering and some outflow/cold
pool propagation southeastward may reduce ideal training setup
given weaker instability totals, but risk of 2-3" totals in 2-3
hours may result in localized flash flooding. This only increases
in proximity to DFW urban corridor, where risk goes up and may be
the only location that these totals may overcome the higher FFG
given drier 30-50% soil saturation environment along and east of
I-35...though saturation increases toward the Texarkana region,
hence the inclusion of the area at this time. As such, a incident
or two of flash flooding is considered possible in the near-term.=20


Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_0Q92CWVPg1fjm9lGxImqhznbTs7LPIRekyUZg4JCUizngcJcy2cG-pCf62ScdIFVIjE= ApfoMoqXUQ4VO-_ZsLljK8Q$ for graphic product...

ATTN...WFO...FWD...LZK...OUN...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34729428 34249336 33499368 32819472 32049641=20
31759835 32379852 33159788 33879686 34449568=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 241851
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-250030-

Mesoscale Precipitation Discussion 1186
NWS Weather Prediction Center College Park MD
150 PM EST Tue Dec 24 2024

Areas affected...Northeast Texas...Southwest Arkansas...Northwest
Louisiana...

Concerning...Heavy rainfall...Flash flooding possible

Valid 241850Z - 250030Z

SUMMARY...A low-end threat of flash flooding continues with slow
southeastward drift of frontal zone within favorable training/
back-building regime.

DISCUSSION...18z Surface analysis shows a triple point of digging
cold front and retrograding sliver of dry line near BBD. A cold
front connects up to a surface wave near Denton before flattening
further into the Red River Valley just north of Texarkana.
GOES-Visible imagery shows the effective warm sector with field of
cu across the majority of E TX, becoming more dense closer to the
coast given slightly higher Tds in the mid 60s and Temps nearing
upper 70s; with the exception of a pocket of low level stratus
that impeded filtered solar radiation across the Hill Country
generally west of HLR/EDC/T20/BEA. The western Gulf return
moisture flow is solid east of this shallow stratus with 20-25kts
of flow increasing toward 30-35kt nearing the front. However,
there is a bit of veering that has slightly reduced deep layer
convergence, likely in continued response to the exiting shortwave
across NW AR and an associated diffluence wedge of 3H ascent
across north Texas. This continues to support isentropic
slantwise ascent across the DFW metro into NE TX in proximity to
the frontal boundary and the convergence is maintaining some
convective cells into northeast TX, though weaker lapse rates due
reduce MUCAPE values below 750 J/kg before reaching SE OK/SW AR
where broader moderate shield precipitation continues.

Recent RADAR mosaic and GOES-E Visible shows some upstream
redevelopment in the core of the peak MLCAPE maxima on the NE side
of the stratus where mid-level SWly flow is providing mid-level
drying and increased lapse rates; near Hamilton county to Bosque
county where values are slowly increasing from 1000 J/kg to 1500
J/kg with further heating. Moisture flux/pooling in/near the
boundary will aid low-level convergence to support rainfall
production with capability of 1.5"+/hr rates similar to this
morning's bout that could occasionally tick up to 2"/hr IF
prolonged training deepens moisture profile in depth. As cold
pool generation may overcome due to evaporative cooling; it will
be a storm scale interaction balance and most likely be widely
scattered in nature and limited in duration and therefore
coverage. Still, this may result in localized 2-3" totals in
less than 2-3 hours. Unlike earlier this morning, the line of
convection is less likely to track through larger urban, more
hydrophobic ground conditions and rainfall totals are are the
lower end of exceeding the slightly higher FFG in the region.=20
Still, an isolated case of FF still remains possible.

Downstream into far NE TX/SW AR...
Instability is likely to continue to be the limiting factor but
stronger isentropic ascent and with increasingly confluent
850-700mb moisture streams may allow for a broader shield
precipitation to form with occasional embedded convective cores
that ramp up run-off in the short-term. Increasingly deeper
cyclogenesis should also enhanced WAA/moisture flux to the region
that this activity may increase toward end of daylight hours with
rates of 1-1.5"/hr scattered within the deeper unidirectional
steering flow. Similar 2-3" totals may exist and while not as
flashy in nature given the longer duration; isolated flooding
conditions may evolve though 00z across NE TX into SW AR where
soil saturation values are more average to slightly above average
per NASA SPoRT 0-40cm RSM fields.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9W_4Km_meX7XjyHBudaT4ZRzje7Nt7oiosYUguFSu0i2-PU2qCspQKMl-jCRV2_Ee7vV= RNcKvVR8VUqy5oX31McLl_A$ for graphic product...

ATTN...WFO...FWD...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34009441 33639344 32849310 32149370 31639564=20
30989700 31119823 31889820 32599750 33519600=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 250033
FFGMPD
LAZ000-TXZ000-250600-

Mesoscale Precipitation Discussion 1187
NWS Weather Prediction Center College Park MD
733 PM EST Tue Dec 24 2024

Areas affected...east-central/southeastern TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 250030Z - 250600Z

SUMMARY...A few areas of flash flooding, especially across urban
locations, will be possible through 06Z for portions of east-central/southeastern TX. Rainfall rates of 2 to 3 in/hr are
expected but should remain localized.

DISCUSSION...00Z surface observations showed a complex depiction
of effective boundaries in place over central and eastern TX, but
with two of the more significant features driving ongoing
convection being a wavy stationary front and southward extending
trough axis south of the DFW metroplex and the leading edge of
higher theta-e air which extended from near RWV to GLS.
Thunderstorms were scattered across the region but have recently
been increasing along/ahead of a pre-frontal trough axis/wind
shift located east of I-35 and extending to just south of SSF. SPC
mesoanalysis showed uninhibited MLCAPE of 500-1500 J/kg within the
warm sector of the wavy stationary front to the north, and 2000+
along the middle to lower TX coast. Anomalous moisture (PWATs 1.0
to 1.4 inches) combined with favorable instability/shear profiles
have allowed for organized cells with slower cell motions than the
deeper-layer mean wind of 15-25 kt. One of these slower cells
resulted in observed 2-3 in/hr rainfall rates in a southeastern
Houston suburb ending 2330Z with MRMS showing occasional/spotty
rates in the 2-3 in/hr since 21Z over north-central TX.

As the base of a mid to upper-level trough continues to amplify
over central TX early tonight while translating eastward, forcing
will be aided by diffluent flow downstream over eastern TX.
Thunderstorms are likely to continue expanding near the southward
extending trough axis over east-central TX within the reservoir of
instability as well as near the quasi-stationary fronts over
northeastern and southeastern TX. Mean/unidirectional southwest
flow is likely to allow for some training and repeating cells with
increasing 850 mb winds overnight (up to ~25 kt) possibly
supporting slower cell movement and brief backbuilding. Localized
2-3 in/hr rainfall rates will be likely with isolated 2-3 hour
rainfall totals of 3-5 inches possible.

While soils have been fairly dry over this portion of TX over the
past couple of weeks and FFG values are fairly high (3-5 inches in
3 hours), overlap of heavy rain with any urban areas will
exacerbate flash flood potential due to poor drainage of these
potential higher rates. A few areas of flash flooding will be
possible, but the threat is expected to remain relatively
localized.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-M72DAobPLmIhD3qOMgraYugFl6_6YsSHFXYQOW4cO0fOt8RNy_yOJE7iEgTmbQZ9GQb= 5OaACXjPjHbWotmP9jG6qb4$ for graphic product...

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 32609438 32559392 32129359 31049383 29779491=20
29189635 28709829 29119879 30659714 31539649=20
32149586 32479506=20

=3D =3D =3D
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AWUS01 KWNH 250604
FFGMPD
TXZ000-251200-

Mesoscale Precipitation Discussion 1188
NWS Weather Prediction Center College Park MD
103 AM EST Wed Dec 25 2024

Areas affected...Southeast TX, including Middle and Upper TX Coast

Concerning...Heavy rainfall...Flash flooding possible

Valid 250600Z - 251200Z

Summary...Flash flooding remains possible overnight with localized
rainfall rates of 1-3"/hr and additional short-term totals as high
as 3-5" (favored in the vicinity of Victoria and around the Middle
TX Coast).

Discussion...A digging shortwave trough is driving a complex of
thunderstorms over portions of Southeast TX, gradually moving
towards the Middle and Upper TX Coast. Peak rainfall rates have
generally ranged from 1-2"/hr, though occasionally have peaked
between 2-3"/hr along the southern end of the complex (per MRMS
estimates). The mesoscale environment is characterized by ML CAPE
of 500-1750 J/kg, precipitable water values of 1.2-1.4 inches
(near the 90th percentile for late December, per CRP sounding
climatology), and deep layer (0-6 km shear) of 25-50 kts (with
both instability and shear maximized in the vicinity of Victoria).

Going forward, the expectation is for the complex of thunderstorms
to remain active until near dawn, particularly along the southern
portions of the complex. Not only is this the best environment for
discrete convection, but supercells have already favored this area
with bunkers right motions supporting slow storm motions (10-15
kts). With both the strongest and slowest convection near the
Middle TX Coast, the highest localized totals of 3-5" are possible
here (per 00z HREF 40-km probabilities for 3" exceedance of
30-50%, as well as more recent runs of the HRRR indicating totals
near 5"). Farther north (including the greater Houston metro
area), lower instability and a stronger cold pool should support
weaker and faster storm motions, generally limiting additional
totals to the 1-2" range.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6yI9FnMjRfliJHO1AgUChmY7PJv3qFXeb6DtnVXuVPConpX-9354XnRHjm7cJEPIGE1y= n-z-dHGCYjoZH5TvTpfGOs0$ for graphic product...

ATTN...WFO...CRP...EWX...HGX...LCH...

ATTN...RFC...WGRFC...NWC...

LAT...LON 30979476 30979413 30629412 29899440 29399466=20
28959495 28439573 27929684 28799819 29419813=20
29939697 30449603 30769531=20

=3D =3D =3D
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AWUS01 KWNH 251703
FFGMPD
ORZ000-WAZ000-260300-

Mesoscale Precipitation Discussion 1189
NWS Weather Prediction Center College Park MD
1202 PM EST Wed Dec 25 2024

Areas affected...Western WA...Western OR...

Concerning...Heavy rainfall

Valid 251700Z - 260300Z

SUMMARY...Strong deepening dynamics will back winds toward more
favorable orographic ascent by 19-20z and increase rainfall
efficiency to near .5"/hr in favored spots by 00-03z. Runoff will
likely increase stream flows, but flooding is not expected quite
yet except for the most vulnerable/traditional locations.

DISCUSSION...GOES-W WV suite shows a compact shortwave crossing
the Southeast Gulf of AK at the far southeast edge of the global
scale trof that has been dominating the Bering Sea. The compact
wave as a solid negative tilt to it associated with a broad strong
polar Pacific Jet with a 150-170kt 250mb streak supporting solid
low level strengthening wind profile with a strong warm front
starting to press eastward with 700-500mb moisture flux & WAA
resulting in lighter showers across W WA and NW OR at this time.=20
Low level winds continue to strengthen with 40-50kts at 850-700mb
per LGX VWP but remaining mainly parallel to the coast, but
increasing reflectivity and polar microwave passes suggest warm
front is approaching quickly and will veer the wind profile toward
21z across W WA and W OR. This will be accompanied by the core of
the sub-tropical moisture stream; with leading 850-700mb moisture
advected on 60-70kts of flow with IVT values increasing from 400
kg/m/s toward 600 kg/m/s. Upslope component on the SW facing
Olympics and Willapa Hills will see first brunt with .33"
increasing to near, occasionally reaching .5"/hr rates by 00z=20
when winds start to peak near 80kts from the SW and IVT peaks near
850-900 kg/m/s. Rainfall totals of 1.5-2.5" by 03z, are likely to
fully saturate the remaining capacity of the upper soils.=20
Currently, much of the area is about 70-80% capacity through 40cm
and while a lot, this is above average in the 70th percentile near
the coast but increasing toward 75-80th percentile in the higher
elevations and further inland. As a result, increased run-off
will be channeled to the streams; and while this is a strong AR,
the duration is not expected to be long to result in any sizable
flooding but increase stream flows in preparation for subsequent
AR surges over the following days.

As the front passes winds will slacken and veer to more due west
and much of NW WA will be out of the core of the AR moisture plume
with .5-.75" PWATs...while shifting into W OR with 1 to nearing
1.25" total PWats. This will maintain stronger rates in the
coastal range of W OR for a few more hours before the next
wave/lifts northward later on Thursday morning. Still by 03z,
west facing orography in NW OR will experience 1-2.5" of rain even
to the tops of the peaks, while .5-1" totals are expected in the
lower valleys (less than .25" in traditional shadowed locations.=20
Similarly, a good soaking and setting the stage for a likely
active pattern of AR pulses though the weekend; however flooding
is not likely to be an issue with exception of the most susceptible/traditionally flooded areas.=20=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!63vZsNSo0SPkto2ZrbQyGX2WJrtCI8bhV8c3R_XIBrhaaKP1qCVuF8-99Dy7psvvqQ-i= zaXcC8QSeEM7PLM8UuUHVrA$ for graphic product...

ATTN...WFO...MFR...PQR...SEW...

ATTN...RFC...NWRFC...NWC...

LAT...LON 48462444 47932366 47282319 46322307 44672328=20
43912349 43612382 43492435 43922463 44862442=20
45692426 46592439 47372467 47862493 48182502=20
48312497=20

=3D =3D =3D
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AWUS01 KWNH 260301
FFGMPD
CAZ000-ORZ000-WAZ000-261500-

Mesoscale Precipitation Discussion 1190
NWS Weather Prediction Center College Park MD
1000 PM EST Wed Dec 25 2024

Areas affected...Western WA...Western OR...Far Northwest CA

Concerning...Heavy rainfall

Valid 260300Z - 261500Z

SUMMARY...Atmospheric river activity continues across the Pacific
Northwest with areas of heavy rain expected to persist into early
Thursday morning before weakening.

DISCUSSION...GOES-W Airmass RGB satellite imagery shows a strong
shortwave trough amplifying offshore of the Pacific Northwest, and
this is driving a rapidly deepening area of low pressure near 45N
131W. This approaching low center along with a strong upper-level
jet on the order of 130 to 150+ kts at 250 mb will continue to
drive a well-defined atmospheric river into the Pacific Northwest
overnight with a gradual southward shift of the higher PW axis/IVT
core by early Thursday morning as a cold front gradually arrives
and begins crossing the region.

IVT magnitudes are expected to peak over the next 3 to 6 hours
across the coastal ranges of far southwest WA, western OR and far
northwest CA with values impressively reaching as high as 800 to
1200 kg/m/s. However, the offshore energy and attendant cold front
is quite progressive and thus these enhanced IVT parameters are
not expected to persist for too long. The IVT values are forecast
by the 18Z GFS and 12Z ECMWF to steadily weaken by 12Z as the cold
front advances inland along with the corridor of stronger low to
mid-level flow.

Rainfall rates overnight are forecast to generally be on the order
of 0.25" to 0.50"/hour with occasional 0.50"+ rates expected for
especially the southwest facing slopes of the coastal terrain. The
most recent HREF guidance suggests portions of southwest OR and
far northwest CA will generally have the highest probabilities of
seeing these rates, with peak rates potentially here reaching as
high as 0.75"/hour as the cold front arrives later in the night.

By early Thursday morning, the rates are forecast to be weakening
overall, but there will be some post-frontal instability and
persistence of onshore flow to keep shower activity going that may
foster some additional brief heavy rainfall rates. A consensus of
the latest HREF guidance supports additional rainfall totals on
the order of 2 to 4 inches going through early Thursday morning
(15Z/7AM PST) across the orographically favored higher terrain,
and especially the coastal ranges.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8M49YNk1dZh0T4I6mLeXxA08cPYpvQHh3Td323rWZpzqOpGY-HOXXE4-RDpq1HIAuSTx= yjBfKQ0ENUv6OEEPMdRPsBE$ for graphic product...

ATTN...WFO...EKA...MFR...PDT...PQR...SEW...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 47872325 47542211 46972182 46442176 45442171=20
44512185 43832202 43142230 42212222 41632232=20
41052297 40082311 39822346 40102428 41142453=20
42522470 44752434 46162436 47322425=20

=3D =3D =3D
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AWUS01 KWNH 261401
FFGMPD
TXZ000-OKZ000-261930-

Mesoscale Precipitation Discussion 1191
NWS Weather Prediction Center College Park MD
901 AM EST Thu Dec 26 2024

Areas affected...Northern Texas...Southeastern Oklahoma...

Concerning...Heavy rainfall...Flash flooding possible

Valid 261400Z - 261930Z

SUMMARY...Warm advective wing of highly dynamic cyclogenesis
already breaking out elevated convection. Continued increasing
moisture flux and slow instability advection to increase rainfall
rates to 1.5"/hr crossing areas of recent heavy rainfall.=20
Short-term training elements pose risk of localized possible flash
flooding.

DISCUSSION...A very strong and sharp shortwave can be seen moving
out of the Texas Panhandle into western OK. A strong digging
100kt jet parallel to the Front Range of the Rockies decelerates
sharply before rounding a slowly negatively tilting trof across
the Big country then rapidly accelerating into 100-105kt SSW jet
across the MOKSAROK placing much of northeast Texas into a very dynamic/favorable upper-level pattern for rapid evacuation and
strengthening low level flow...as noted by transverse banded
activity across the Big Country. Deep layer moisture has been
limited to the Gulf; but recent CIRA LPW suite denotes that the
strengthening low level jet in response to the height-falls is
advecting increasing moisture and higher theta-E across central TX
toward the region.

The nose of the MUCAPE axis has recently nudged into the area of
ascent with 500 to 750 J/kg being analyzed; and as such, recent
convective towers have been forming along the northeast edge of
the Hill country with active increasing lightning detected.=20
Strong WAA pattern from the SW through 700-500mb, indicates the
strong steering pattern; but with the low level moisture and WAA
response, redevelopment along the effective boundary slowly
lifting northeastward across N TX, will allow for some convective
elements to have a training profile. This training/back-building
potential is likely to be the main key/driving factor to localized
flash flooding as well as crossing areas recently saturated from
prior rainfall two days ago. NASA SPoRT 0-40cm denotes a sharp
gradient of soil saturation along I-35, becoming 50-65% saturated
toward northeast TX; however, AHPS 7 day anomaly shows those
deeper saturation may extend a county or two further west;
increasing the potential to intersect with the heavy rainfall.

Cells are likely to be a bit more moisture starved given limited
mid to upper level moisture and the training is likely to help
over come it. However, the strength of ascent and focused
convergence in banded convective lines may allow for .5"/hr to
increase to 1.5"/hr throughout the late morning into early
afternoon hours with increased moisture flux. As such, streaks of
1-3" totals are probable through the morning with slow
northeastward expansion of the WAA. This places the rates and
totals near or slightly above the lowered FFG values across the
area of concern into SE OK; so localized exceedance is possible
with increased potential in and around the urban DFW corridor.=20=20
As such, flash flooding is considered possible.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7-lwxPQ-ppsZeC5-MLk-uR9jROzDzUapNNWF7iakQfIoO1oPbEoLcDJr0cI4ugbnYljw= Txlo75z-qsOIWKVuiuEnTVY$ for graphic product...

ATTN...WFO...FWD...OUN...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34969605 34879539 34399470 33709458 32999468=20
32499532 32069612 31599769 31689832 32309881=20
33299863 34219764 34679693=20

=3D =3D =3D
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AWUS01 KWNH 261642
FFGMPD
TXZ000-262230-

Mesoscale Precipitation Discussion 1192
NWS Weather Prediction Center College Park MD
1141 AM EST Thu Dec 26 2024

Areas affected...East Central and Southeast Texas...

Concerning...Heavy rainfall...Flash flooding possible

Valid 261645Z - 262230Z

SUMMARY...Increasing convection is developing along confluence
lines within the strengthening warm conveyor belt. Upstream
moisture flux/instability advection likely to aid in storm-scale
backbuilding resulting in periods of training. Rates increasing
from 1.25 toward 2"/hr by 21z will allow for localized spots of
2-4" in the next 6 hours. Localized flash flooding will be
possible.

DISCUSSION...A highly dynamic setup is trying to rapidly evolve an strengthening thermodynamic environment conducive of strong
thunderstorms with intense rainfall potential for this evening.=20
However, in the interim, smaller pockets of unstable air and
strong dynamic ascent patterns will produce widely scattered cells
that will have the capability of producing locally 2-4" totals by
22z and may induce localized flash flooding.

GOES-E WV suite shows a highly amplified upper level pattern with
dual jets flanking a weakly negative tilt orientation across the
Red River Valley into central TX; the upstream jet across E NM is
about 110-120kts decelerating and descending across the Hill
country before rounding the base and entering a broad
strengthening 100 kt jet entance across much of central TX into E
OK, though broader diffluence is supportive of divergence aloft
across the Mid-Texas Gulf Coast into SE TX. attm. The old
stationary boundary extends from near Ardmore to west of DFW metro
toward Austin and just west of BEA/NOG under influence of the
highly unstable western Gulf of Mexico. The strengthening LLJ
aligns with the natural confluence of the western Gulf and is
surging deeper moisture/instability along a rising warm coastal
front through the Coastal Plain at this time; intersecting with
the old surface boundary near KT20. This LLJ will act as a solid
warm conveyor belt with embedded N-S confluence lines until the
main upper-level height-falls and effective mid-level cold front
presses south and eastward into the evening hours. The building
heat from slightly clearing skies has brought temps in the low 70s
with similar high 60s and low 70s Tds and increasing MLCAPEs to
1500-2000 J/kg with the warm front. Convergence from
southeasterly surface low should provide sufficient convergence
for scattered thunderstorm development. Recent Lightningcast
products have been rapidly increasing signals throughout the warm
sector with a few cells even further north into east-central TX;
with expected further expansion with further surface
heating/instability growth.

Cells that do develop will be ingesting solid 1.25-1.5" total PWat
air within 30-35kt increasingly confluent flow, which should
support back-building environment. Given the 850-700mb warm
sector low-level shear profiles will support solid bulk shear
values for organized updrafts with some rotation, further
increasing moisture flux convergence and loading in the lower
profile for efficient rainfall production. Rates of 1.25"/hr will
increase to near 2"/hr over the next 6 hours and while coverage is
likely to be more scattered in nature initially, the backbuilding
and favorable orientation of convergence bands to the mean
steering will allow for short-term periods of localized training
to allow for some localized spots of 2-4"; with greater
probability initially closer to the coast and along the rising
warm front. This may intersect areas that received 2-4" of rain
two days ago, as NASA SPoRT 0-40cm soil saturation ratios are
modestly high particularly north and east of the Houston Metro,
but there were some spots southwest that show 200-400% above
normal precip anomalies on AHPS. With all this considered
scattered incidents of flash flooding are considered possible
before evening but will be increasing with time (and after 22z)
across the area of concern.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!83k89vQkL0se-6SxlNfGWD-VH7qKLS8PCzmL9AIX5ULv-DJljqIl3izLKVzxx1HlQKCv= ZErtIX9-PAavlPWwysaZmIk$ for graphic product...

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON 32249475 31939413 31449382 31059379 30229390=20
29509439 28239651 28449693 29519697 30789716=20
31529678 31979601 32219541=20

=3D =3D =3D
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AWUS01 KWNH 261856
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-270100-

Mesoscale Precipitation Discussion 1193
NWS Weather Prediction Center College Park MD
156 PM EST Thu Dec 26 2024

Areas affected...Northeast TX...Southeast OK...Far Southwest AR...

Concerning...Heavy rainfall...Flash flooding possible

Valid 261900Z - 270100Z

SUMMARY...Reducing instability, rainfall efficiency; but slower
moving cells with some training pose spots of 2-3" and widely
scattered possible flash flooding through evening.

DISCUSSION...The window for excessive rainfall inducing localized
flash flooding is starting to close due to multiple factors; one
being convection moving into areas of higher FFG, though still
equally saturated in the 0-40 cm layer with NASA Sport RSM still
in the 60-70% range. The second is reducing moisture flux and
available instability. Yet, a training steering profile still
remains as well as potential for stationary cells near the
pivoting deep layer cyclone over Northern Texas toward 00z.

Currently, regional RADAR mosaic and GOES-E suite of imagery show
the decaying convection along the effective 850-700mb warm front
across NW LA/SW AR angling back to the developing deep layer pivot
of the cyclone over the central Red River Valley between North and
Northwest Texas. Strong height-falls as the upper-level jet and
5H trough swing more negative tilt across central to northeast
Texas; the effective 850mb cold front is aligning to the surface
and is pressing much faster eastward to the south. A mid-level
dry slot/descent channel is starting to pinch in proximity to
Falls, Robertson and Bell county and the LLJ is starting to take a
more branched appearance as the confluent flow increases
convective activity along the trailing convergent southwesterly
flow and effectively severs the best deep layer moisture transport
along and ahead of the effective 850mb advancing front.=20

Currently, the window is still open and MUCAPE values 750 J/kg
nosing toward 1000 J/kg are still within access and ascend through
the western branch of the TROWAL to maintain/promote convective
activity across the Heart of Texas region. The southerly backing
30kt flow is supporting 1.25" total PWats mainly below 700mb to
providing solid flux convergence for efficient rainfall production
for the next few hours with rates of 1-1.25" slowly diminishing
with time. Deep layer steering at the nose/left rotor of the
developing dry slot may allow for cells to angle sufficiently for
some short-term SW to NE training from Freestone/Navarro county
region to Red River/Cass counties over the next 4-6 hours. As the
dry slot severs the connection rates will drop below 1"/hr and
overall totals will reduce to less than the rising FFG values in
far NE TX, reducing the potential for low-end flash flooding
conditions.

A secondary risk may start to occur near the pivot of the deep
layer cyclone as it crosses North Texas toward 00z. Steepening
lapse rates and remaining modest pooled moisture and convergent
flow along the southeast quadrant may spark a few narrow core
convective cells. Deep layer steering will be near zero near the
center of the low, allowing for Subtle Heavy Rainfall Signature
(SHaRS) events with 1-1.5"/hr rates falling over areas having
recently experienced prolonged moderate shield precipitation
across the Red River Valley and across into S OK. These would be
very spotty in nature, but the intensity of the rates in such a
small area could pose a localized flash flooding risk as well.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6UeAJSEdlBDof7NCT1FAGCfMmd71AcYjg4AgLFxxQkSypyZ3Uumopuv5xMQCBmxZvgts= T2blZsW2fz5MmAwGwxQv8HU$ for graphic product...

ATTN...WFO...FWD...OUN...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34419525 34109433 33619364 32979395 32289460=20
31229645 32409692 33729715 34299646=20

=3D =3D =3D
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AWUS01 KWNH 262358
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-270500-

Mesoscale Precipitation Discussion 1194
NWS Weather Prediction Center College Park MD
658 PM EST Thu Dec 26 2024

Areas affected...southeastern TX into western LA

Concerning...Heavy rainfall...Flash flooding likely

Valid 262356Z - 270500Z

SUMMARY...Training and repeating of thunderstorms will continue a
flash flood threat from southeastern TX into western LA through
05Z. Rainfall rates of 1-2 in/hr and localized totals of 2-4
inches can be expected.

DISCUSSION...Regional radar imagery at 2330Z across the South
showed a line of thunderstorms extending from northwestern LA into
the Piney Woods of southeastern TX with a second line extending
from Jasper/Newton counties to roughly Matagorda Bay. These storms
were occurring just ahead of a pre-frontal trough/wind shift
located east of a cold front moving through east-central TX. SPC
mesoanalysis data from 23Z showed PWATs of 1.4 to 1.7 inches
coincident with the thunderstorm axis and MLCAPE of 500-2000 J/kg
from the central TX/LA border to the mid TX coast. Favorable shear
profiles ahead of a potent mid-level vorticity max (over north TX)
have supported supercells with enhanced rainfall rates while mean
steering flow from the southwest has resulted in areas of training
and/or repeating rounds of heavy rain from the northern TX/LA
border into the southeastern TX Coastal Plain.

Over the next 3-5 hours, the best upper level support (PVA, upper diffluence/divergence) will shift eastward from the Arklatex into
northern LA/southern AR. However, RAP forecasts of instability
show only a small pocket of 500-1000 MUCAPE just ahead of the
mid-level low center which should be steadily tracking east
through the first half of tonight. Due to lower instability
profiles, a lower end flash flood threat will exist for these
northern locations where strong forcing will should be balanced by
a fairly progressive translation of heavy rain toward the east and
limited instability.

Farther south, a lack of height falls for the Gulf Coast region
should result in a slower eastward progression of heavy rain. It
is here where greater instability is forecast to reside within the
warm sector (500-1500 J/kg MLCAPE). 850 mb winds of 40-60 kt from
the southwest and similarly oriented mean steering flow will allow
for areas of training and repeating thunderstorms capable of 1-2
in/hr (perhaps locally above 2 in/hr) due to a slower eastward
progression to the axis of thunderstorms. 2-4 inches of rain over
a roughly 2 hour window is expected to result in a couple of areas
of flash flooding through 05Z from southeastern TX into western LA.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-CVMsN44zV6cl5EGyQ9kxK4q073aGWwSlZREmXdpQRwVl8YWclCSHggBiLiwR3Lwqe2B= _T9ceaMmzLObBgV_elWJF50$ for graphic product...

ATTN...WFO...HGX...JAN...LCH...LZK...SHV...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 33949177 33509109 32649100 31619139 30769200=20
29699292 29499407 29039513 29219549 30059521=20
31439447 32449392 33769307=20

=3D =3D =3D
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AWUS01 KWNH 270246
FFGMPD
CAZ000-ORZ000-271200-

Mesoscale Precipitation Discussion 1195
NWS Weather Prediction Center College Park MD
945 PM EST Thu Dec 26 2024

Areas affected...Southwest OR...Northern and Central CA

Concerning...Heavy rainfall

Valid 270245Z - 271200Z

SUMMARY...New atmospheric river surge arriving overnight will
bring additional rounds of heavy rainfall and potentially some
localized flooding and runoff concerns.

DISCUSSION...The latest GOES-W Airmass RGB satellite imagery shows
a new shortwave trough amplifying offshore of the West Coast which
will drive a new area of cyclogenesis overnight. The developing
low center will arrive across the coastal ranges of northwest OR
and southwest WA by early Friday morning. To the south of this low
center will be a renewed deep layer fetch of Pacific moisture that
will overrun the coastal ranges down the coast, and especially
across southwest OR and into northern and central CA.

A warm front offshore of the West Coast will be approaching as
rather strong IVT magnitudes encroach on the region. Enhanced low
to mid-level flow around the southern flank of the shortwave
trough will drive IVT values upwards of 750 to 1000 kg/m/s at
least for several hours (generally between 03Z and 09Z) as the
warm front arrives and advances inland. Later tonight and toward
12Z, the low center entering the Pacific Northwest will drive a
cold front inland across the coastal ranges.

PWs are forecast to reach as high as 1 to 1.25+ inches, and
reaching locally as high as 2 to 3+ standard deviations above
normal with the greater anomalies forecast to set up in the 06Z to
12Z time frame down across the Bay Area. Even areas a bit farther
south down the coast around Monterey are expected to see a notable
increase in PWs overnight as this latest atmospheric river surge
arrives.

The latest HREF guidance shows rather high probabilities of seeing
at least a few hours of potential 0.50"+/hour rainfall rates
impacting the orographically favored terrain from southwest OR
down through northwest CA and also portions of the Bay Area in the
06Z to 12Z time frame. Some of these heavier rains may also at
least locally spillover into the far northern Sacramento Valley
and the foothills of the northern Sierra Nevada, but generally the
heaviest rates should be across the coastal ranges. This will
coincide with the strongest window of forcing from warm air
advection and higher IVT parameters. After 12Z, the rates should
diminish rather substantially as the energy associated this latest
system advances rapidly inland.

Additional rainfall totals going through 12Z (4AM PST) Friday
morning are expected to reach 2 to 3 inches with isolated heavier
amounts possible. Given the wet antecedent conditions, these
additional rains may result in some localized flooding concerns
and this will include some urban flooding potential around the Bay
Area tonight.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8784PPpwQjwvhq15F2dET7JKppLElsnfqNyj9XokRKUxZ74gHfsylSnY2rK2uCnw_wQK= 8WHCS1WHNlAuclfAjx9eiDQ$ for graphic product...

ATTN...WFO...EKA...MFR...MTR...REV...STO...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 43142392 42382323 41932229 41422172 41052171=20
40552133 40062088 39642075 39182077 39102137=20
40002199 39922247 39572247 38952222 38262196=20
37342135 36822148 36582193 36972258 38182341=20
39262412 40792456 41792449 42912460=20

=3D =3D =3D
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AWUS01 KWNH 270501
FFGMPD
MSZ000-LAZ000-ARZ000-271100-

Mesoscale Precipitation Discussion 1196
NWS Weather Prediction Center College Park MD
1201 AM EST Fri Dec 27 2024

Areas affected...Southwest and Central LA...Western and Central MS

Concerning...Heavy rainfall...Flash flooding possible

Valid 270500Z - 271100Z

SUMMARY...A broken axis of heavy showers and thunderstorms will
continue to foster a localized threat for some flash flooding
overnight across portions of southwest to central LA through
western and central MS.

DISCUSSION...The latest GOES-E IR satellite imagery shows a
vigorous shortwave trough and compact low center transiting the
Lower MS Valley which continues to foster a rather well-organized,
but broken axis of heavy showers and thunderstorms. The activity
has waned somewhat over the last couple of hours as the stronger
mid and upper-level dynamics begin to lift away from the area of
greater instability pooled closer to the Gulf Coast, but the
low-level flow remains rather strong and convergent. In fact, the
area VWP data continues to show a 40 to 50+ kt low-level jet
surging northward up toward the Mid-South from the Gulf Coast and
this is maintaining a corridor of strong moisture transport and
convergence along and just ahead of a cold front.

MUCAPE values of 1000 to 1500 J/kg are still noted across areas of
southwest LA which taper down to 500 to 1000 J/kg across central
LA and into far southwest MS. The level of effective bulk shear
that is in place remains quite strong and is locally exceeding 50
kts which is still favoring a fair degree of convective
organization with the band of thunderstorms including some
supercell structures. These stronger cells will continue to have
the capability of producing very heavy rainfall rates that will
locally reach 1.5 to 2.5 inches/hour, and this will be aided by
PWs of near 1.5 inches and the aforementioned low-level jet.

The 00Z HREF guidance suggests that some southwest to northeast
training of these more organized cells may still occur at least
locally going through the overnight hours, with some spotty swaths
of 2 to 4 inch rainfall totals possible. As a result, the
convective activity is expected to still foster a localized threat
for some flash flooding and especially within any of the more
urbanized corridors.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8AYKJQYCJzdlGJ1DnlsKVi-y-Vy0y68r4TY_Gx05VUkCCrk_D2j8_DfV9ZoNz4PbNAeT= _RwPP91ja-S6tHrJH66gD4o$ for graphic product...

ATTN...WFO...JAN...LCH...LIX...MEG...SHV...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 33929018 33838931 33338915 32638945 32049000=20
31549046 30729121 29619243 29509306 29759358=20
30539289 31749210 33299114=20

=3D =3D =3D
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AWUS01 KWNH 280123
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-280630-

Mesoscale Precipitation Discussion 1197
NWS Weather Prediction Center College Park MD
822 PM EST Fri Dec 27 2024

Areas affected...southern MS/AL into far western FL Panhandle

Concerning...Heavy rainfall...Flash flooding possible

Valid 280121Z - 280630Z

SUMMARY...A threat for training will be heightened across southern
MS into southern AL and far western FL through at least 06Z. The
potential for localized flash flooding from rainfall rates in the
1-3 in/hr range will exist.

DISCUSSION...Regional radar imagery across the central Gulf Coast
at 0115Z showed a SW to NE oriented axis of thunderstorms
stretching from the southern coast of MS into central AL. A second
axis, with only a widely scattered coverage of cells, was present
from the offshore waters south of the MS/AL border into portions
of far southern AL. The environment along and southwest of a
stationary front extending through southern MS/AL contained
500-1500 J/kg MLCAPE and 1.5 to 1.7 inch precipitable water values
(per 01Z SPC mesoanalysis and 00Z LIX sounding). Low level
confluent flow just above the surface was a main driver in the
ongoing axis of convection but lift within the right-entrance
region of a departing 100 kt upper level jet streak over the OH
Valley may also be contributing to ascent across the Deep South.

As a shortwave and associated jet energy continue to pull away
from the region tonight, greater synoptic lift will be weakening
but the low level confluent flow is expected to remain from far
southern MS into southern/central AL with a gradual eastward
translation with time. Instability and moisture parameters will be
supportive of 1-3 in/hr rainfall rates where cells train. Since
FFG values are fairly high (3 to 5 inches in 3 hours), the flash
flood threat should be localized in nature and likely more of an
issue if areas of training focus atop metropolitan regions, such
as Mobile and/or Pensacola. The threat for training and high
rainfall rates is expected to continue until at least 06Z tonight.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!71r839v-_5o6dtr2UdHh9onJgc9ohvM9fxCJDVTYt_8v3LXApt3JgWDndezxxRnFZZol= iUnEg7_i9-z7XwsrVrnv4E8$ for graphic product...

ATTN...WFO...BMX...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 32348685 32208624 31688638 30998660 30228731=20
30058834 29998926 30158951 30418953 30928893=20
31778810 32168757=20

=3D =3D =3D
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AWUS01 KWNH 280307
FFGMPD
CAZ000-ORZ000-281300-

Mesoscale Precipitation Discussion 1198
NWS Weather Prediction Center College Park MD
1007 PM EST Fri Dec 27 2024

Areas affected...Southwest OR...Northwest CA

Concerning...Heavy rainfall

Valid 280305Z - 281300Z

SUMMARY...The latest in a series of atmospheric river surges will
be arriving overnight across southwest OR and northwest CA with a
new round of focused heavy rain over the coastal ranges.

DISCUSSION...The GOES-W Airmass RGB satellite imagery shows
another strong shortwave trough gradually approaching the Pacific
Northwest which will be favoring the arrival of a new area of
deepening surface low pressure near Vancouver Island by early
Saturday morning. To the south of this low center evolution, a
renewed deep layer surge of Pacific moisture and associated
atmospheric river activity will be overrunning the coastal ranges
of southwest OR and northwest CA.

Strong low to mid-level westerly Pacific flow overnight will allow
a warm front to approach the region and advance quickly inland
across northern CA, with a trailing cold front that will then
gradually begin to cross the coastal ranges by early Saturday
morning. IVT magnitudes will rise rather sharply over the next
several hours across especially southwest OR and far northwest CA,
including Coos, Curry and Del Norte Counties, with values
increasing to over 750 kg/m/s by 06Z.

Enhanced warm air advection and moisture transport into the
orographically favored terrain will likely result in rainfall
rates approaching and locally exceeding a 0.50"/hour. The 18Z HREF
guidance shows elevated probabilities (50 to 70 percent) of this
occurring with potentially some brief 0.75"/hour rates occurring
as the IVT values peak overnight just ahead of the approaching
offshore cold front.

The IVT magnitudes will then be dropping off in the 09Z to 12Z
time frame which will allow for the rainfall rates and shower
activity to at least diminish early Saturday morning, but the
aforementioned cold front that arrives will also be tending to
slow down which will keep the front in close proximity to the
coastal ranges of northwest CA through Saturday morning.

Additional rainfall amounts going through 12Z of 2 to 4 inches are
likely for especially the coastal ranges of southwest OR and
northwest CA, with isolated heavier amounts. Given the already wet
antecedent conditions and high streamflows, these rains are
expected to foster at least some localized concerns for runoff
problems and flooding.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5S2qpY0yCgrlh_Xu6QoJd_NKFF2_brL_2Dv6RidVoWup7OYz2RXzF2_zPVJ7mN5N1bJ2= MNpWRLOtTJjCB_69u5oY1Dw$ for graphic product...

ATTN...WFO...EKA...MFR...PQR...STO...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 43822300 43242210 42362196 41802203 41332170=20
40812165 40012113 39812140 40222251 39862285=20
39442332 39442397 40012446 40372455 41322425=20
42042466 42782479 43542448=20

=3D =3D =3D
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AWUS01 KWNH 280412
FFGMPD
FLZ000-ALZ000-MSZ000-281010-

Mesoscale Precipitation Discussion 1199
NWS Weather Prediction Center College Park MD
1111 PM EST Fri Dec 27 2024

Areas affected...Southern MS...Southwest AL...Far Western FL
Panhandle

Concerning...Heavy rainfall...Flash flooding likely

Valid 280410Z - 281010Z

SUMMARY...Extremely heavy rainfall associated with training
showers and thunderstorms is expected over the next several hours
just north of the Gulf Coast involving portions of southern MS,
southwest AL and the far western FL Panhandle. Flash flooding is
already occurring locally and is expected to continue overnight,
including growing concerns for major urban flash flooding.

DISCUSSION...The latest GOES-E IR satellite imagery in conjunction
with dual pol radar shows a corridor of extremely heavy shower and
thunderstorm activity impacting portions of Harrison and Jackson
Counties in southern MS, along with Mobile and Baldwin Counties in
southwest AL. The convection over the last hour has been growing
further in organization with cooling convective tops (as low as
-65C) and the activity showing well-defined cell-training and
backbuilding characteristics.

This convection is being driving by moist, convergent and unstable
low-level flow advancing north in close proximity to a warm front.
This coupled with a focused axis of moisture convergence and
divergent flow aloft is likely to foster a continuation of locally
concentrated and slow-moving showers and thunderstorms with
cell-training concerns going well into the overnight hours.

MLCAPE values of near 1000 to 1500 J/kg have been pooling across
the central Gulf Coast region, and the 00Z RAOB from LIX along
with the latest CIRA-ALPW imagery shows a rather deep column of
moisture in place with PWs of 1.5 to 1.7 inches. This coupled with
as much as 30 to 40 kts of effective bulk shear, and the proximity
of the warm front should favor organized convection capable of
producing rainfall rates as high as 2 to 3 inches/hour with the
strongest cells.

A look at the 00Z HREF guidance suggests additional rainfall
totals going through dawn may reach as high as 4 to 8 inches, and
some localized totals approaching 10+ inches cannot be ruled out
given the enhanced backbuilding and cell-training concerns. Flash
flooding is already occurring, and there will be major urban flash
flooding concerns overnight along areas close to I-10. Areas near
and just to the north of a line from Biloxi, MS to Mobile, AL and
potentially edging east into the far western FL Panhandle north of
Pensacola will need to be very closely monitored overnight for a
threat for locally significant flash flooding.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-Qif0ATdGfBHQYG_-1XDQqcfOslfa8rthM-HBDYZchRAaFAnAyLl9bPt88Te02ozUMxq= 1vdC7YvcR7BpPAdFtrREfTo$ for graphic product...

ATTN...WFO...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 31348709 31028674 30638688 30358737 30258835=20
30378905 30668907 30958868 31278787=20

=3D =3D =3D
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AWUS01 KWNH 281028
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-281625-

Mesoscale Precipitation Discussion 1200
NWS Weather Prediction Center College Park MD
525 AM EST Sat Dec 28 2024

Areas affected...Northern and Eastern TX...Northern LA...Southern
AR...Western MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 281025Z - 281625Z

SUMMARY...Showers and thunderstorms will begin to rapidly develop
and expand in coverage by mid to late morning. Heavy rainfall
rates and wet antecedent conditions will promote increasing
concerns for flash flooding with time.

DISCUSSION...The early morning GOES-E Airmass RGB satellite
imagery shows a mid to upper-level shortwave trough amplifying east-southeastward out of the southern High Plains and advancing
toward the Red River Valley of the South. Increasingly divergent
flow aloft and strengthening shear parameters interacting with the
poleward transport of moisture and instability up across central
and eastern TX will set the stage for rapidly developing clusters
of strong thunderstorms in the 12Z to 15Z time frame across areas
of north-central to northeast TX, with development also then
taking place farther east in close proximity to a warm front over
into areas of northern LA, southern AR and possibly western MS.

This warm front will be an important focus for convection going
toward midday as a strengthening and increasingly convergent
southerly low-level jet reaches 30 to 40+ kts in response to
surface low pressure deepening upstream across north-central TX.
Already there is as much as 1500 to 2500 J/kg of MLCAPE noted over south-central to southeast TX and southern LA which will be
lifting north over the next several hours. The convection should
rather quickly become organized with combinations of multicell and
supercell thunderstorms evolving and growing upscale in a west to
east fashion as stronger upstream forcing arrives in conjunction
with the strengthening low-level jet.

PWs increasing to 1.25 to 1.5 inches coupled with the instability
and strengthening shear will likely favor the stronger storms by
late morning producing rainfall rates as high as 1 to 2
inches/hour, and there will likely be increasing concerns for some
cell-merger activity and cell-training near the aforementioned
warm front. Warm sector convection farther south over areas of
eastern TX will also begin to initiate and evolve by late morning
which will be capable of producing enhanced rainfall rates.

Some rainfall totals of 2 to 4 inches will be possible with the
morning activity, and with the antecedent conditions quite wet
with elevated streamflows across much of eastern TX and into the
Arklatex region, these rainfall amounts are expected to increase
the threat of flash flooding. This will include an urban flash
flood threat from near the Dallas-Fort Worth metropolitan area
eastward over toward Shreveport. More organized coverage of strong thunderstorms (with notable severe weather concerns) along with
heavy rainfall and flash flooding will evolve beyond this period,
and expect more MPDs to be issued accordingly.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4VtrFGxZhdszbz1jCtUQenIjnmV5Yv_41ZrfofGKSvnuqTtrlMLn2MDutfGbQSXldjpg= WH3kujPoD34PLZAZ7XFXOh8$ for graphic product...

ATTN...WFO...EWX...FWD...HGX...JAN...LCH...LZK...OUN...SHV...
TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34119456 34059309 33929136 33259058 32489072=20
31899145 31649230 31249413 30429588 30309690=20
30749739 31419742 31839807 32239820 33089740=20
33699638 33979555=20

=3D =3D =3D
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AWUS01 KWNH 281705
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-282230-

Mesoscale Precipitation Discussion 1201
NWS Weather Prediction Center College Park MD
1204 PM EST Sat Dec 28 2024

Areas affected...eastern TX, northern LA, southern AR,
northwestern MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 281700Z - 282230Z

SUMMARY...Areas of training heavy rain, with rates of 1-3 in/hr,
will affect portions of eastern TX into northern LA, southern AR
and perhaps far northwestern MS through 22Z. Rainfall totals of
3-5 inches in 2-3 hours will be possible across a SW to NE
oriented axis, overlapping TX/LA/AR.

DISCUSSION...Regional radar imagery at 17Z showed scattered to
widespread thunderstorms from the AR/LA border into northeastern
TX. Convection extended roughly near/north of a stationary front
which was analyzed WSW from the MS/AR border into eastern TX at
17Z. Convection transitioned into a QLCS with southeastward bowing
observed across I-20 in eastern TX. Meanwhile, an upstream NNE to
SSW axis of thunderstorms was pressing east along I-35 between ACT
and SAT, located just ahead of a pre-frontal trough/dryline. 30-40
kt of SW 925-850 mb flow was advecting moisture northward through
southeastern TX into the stationary front which marked a gradient
in MLCAPE with roughly 500-1500 J/kg along the boundary via 16Z
SPC mesoanalysis data.

As a potent mid-level shortwave continues to advance east from
central TX today, downstream forcing will increase as an upper
level jet max becomes better defined over eastern OK, placing
right-entrance ascent over the Arklatex to Lower MS Valley. Low
level winds may also increase a little more into the afternoon
ahead of the upper trough axis. Thunderstorms are expected to
continue to expand in coverage ahead of the advancing convective
line near I-35 with low level convergence near the stationary
front aligning with mean SW steering flow to support
training/repeating cores of heavy rain. PWAT coverage of 1.5
inches and greater is forecast to expand across the region,
coupled with more than sufficient instability and favorable shear
to promote organized cells. Thunderstorms will be capable of
producing 1 to 3 in/hr rainfall rates due to training and
repeating rounds could amount to 3-5 inches of rain in a 2 to 3
hour period.

The greatest concern for training and the heaviest rainfall totals
through 22Z will be in the vicinity of the stationary front from
northeastern TX into northern LA/southern AR and perhaps far
northwestern MS. Farther south, while the convective line near
I-35 is likely to remain progressive from west to east, additional
development ahead of the line and periods of short term training
within the convective axis may still promote a threat for flash
flooding across portions of southeastern TX into western LA.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4i5B_CGCd0spZ74-7xxxyMPvLmBC7c-caEj4poEVxog-A1lcfgRu45FBPALHA4_OinGV= Q7HFihBaK-K5Mr1ZVIIl3wA$ for graphic product...

ATTN...WFO...FWD...HGX...JAN...LCH...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34599115 34399049 33749063 32799145 31879208=20
30719287 30099476 30589647 31169716 31819719=20
32369670 32679535 33579389 34119247=20

=3D =3D =3D
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AWUS01 KWNH 282144
FFGMPD
TNZ000-MSZ000-LAZ000-MOZ000-ARZ000-TXZ000-290330-

Mesoscale Precipitation Discussion 1202
NWS Weather Prediction Center College Park MD
444 PM EST Sat Dec 28 2024

Areas affected...far southeastern TX into lower/middle MS Valley

Concerning...Heavy rainfall...Flash flooding likely

Valid 282142Z - 290330Z

SUMMARY...An axis of training heavy rain is expected to produce
scattered areas of flash flooding from far southeastern TX into
the lower/middle MS valley through 03Z. Rainfall rates of 1 to 2
in/hr (locally higher) are expected.

DISCUSSION...Regional radar imagery at 0415Z showed a NE to SW
oriented axis of thunderstorms tracking slowly toward the east
from southeastern AR into LA and far southeastern TX. Cell speeds
were slowest in the vicinity of a quasi-stationary front that was
analyzed from western TN/northwestern MS into southeastern AR,
with a surface low becoming better defined along the front roughly
35 miles west of Monroe, LA. South of this low, a cold front was
moving southeast/east but cells ahead of the front were more
intense than those to the north with generally colder cloud tops,
greater lightning frequency and higher MRMS hourly rainfall
estimates. This was due to the numerous coverage of cells
(including supercells) along/ahead of the cold front near the
lower Sabine River to the MS River, with mergers and brief
training coupling with greater individual cell organization. SPC
mesoanalysis data from 21Z showed 1500 to 2500+ J/kg MLCAPE in
place from the LA/MS border into the southeastern TX Coastal
Plain.

Water vapor imagery showed that a strong shortwave trough over
east-central TX was beginning to take on a negative tilt.
Increasing diffluence and divergence aloft, downstream of the
shortwave, will overspread the lower and middle MS Valley through
the late evening. As this happens, the surface low over northern
LA is expected to organize and track northward up the MS River
Valley. The southward extending cold front will pick up speed and
sweep southeastward across southeast TX and LA. While the forward
speed of the cold front will limit flash flood potential across TX
and portions of LA, multiple rounds with cells in the pre-frontal environment/mergers and brief training will still pose an isolated
flash flood threat for these regions.

Farther north, slow movement of the quasi-stationary front and
increasing low level moisture transport ahead of the organizing
surface low will wrap moisture back to the west, north of the low,
with an expected longer duration of rainfall rates of 1-2 in/hr
and perhaps the highest additional rainfall totals for the region
through 03Z, on the order of 2 to 4+ inches from near the MS River
into northwestern MS and southwestern TN. FFG values are lower for
these northern areas 2-3 inches in 3 hours, and therefore, flash
flooding appears likely.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9w36jnmzsUfUSBYucW5z_D40yqswbGnGbSTvNPgSoLjqC8xkC7mD_LsX7otRtyPAodcm= egr8NDaV1b8KScbomMakKBI$ for graphic product...

ATTN...WFO...HGX...JAN...LCH...LIX...LZK...MEG...SHV...

ATTN...RFC...LMRFC...SERFC...WGRFC...NWC...

LAT...LON 36228927 36068867 35498838 34708850 33298883=20
32028940 30369057 29339295 29559483 30789473=20
31489371 32869292 33719206 35299093 36088987=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 290233
FFGMPD
FLZ000-TNZ000-ALZ000-MSZ000-LAZ000-290830-

Mesoscale Precipitation Discussion 1203
NWS Weather Prediction Center College Park MD
931 PM EST Sat Dec 28 2024

Areas affected...Central Gulf Coast...Mid-South

Concerning...Heavy rainfall...Flash flooding possible

Valid 290230Z - 290830Z

SUMMARY...Strong to severe thunderstorms associated with an
eastward advancing QLCS will continue to foster some potential for
areas of flash flooding going into the overnight hours.

DISCUSSION...The latest GOES-E IR satellite imagery in conjunction
with dual-pol radar shows a well-defined QLCS continuing to
advance off to the east across large areas of the Mid-South with
an extension essentially from northern MS south-southwestward down
into southeast LA. This continues to be associated with a strong
mid-level trough ejecting out of the Lower MS Valley and lifting
toward the Mid-South as it gradually takes on a neutral to
slightly negative tilt. Enhanced deep layer ascent and shear
continues to interact with a strong southerly low-level jet of 40
to 60+ kts and this will continue to drive a well-organized axis
of convection downstream across much of the South going through
the overnight hours.

MLCAPE values of 1500 to 2500 J/kg are noted across southeast LA
into far southern MS, and this coupled with higher PWs reaching
over 1.5 inches should tend to drive heavier rainfall rates across
this area with the more organized convective cells that will be
crossing this region over the next several hours. The convection
in general across the central Gulf Coast region including
southeast LA, southern MS and southern AL may tend to take on more
of a southwest to northeast orientation going through 06Z which
will facilitate some areas of cell-training.

Farther to the north, the instability does drop off rather
considerably, and especially for areas up across northern MS,
northern AL and through middle TN, but with such strong dynamical
forcing crossing this region, there should still be at least some
broken QLCS activity that fosters heavy rainfall. This portion of
the overall convective axis is certainly more progressive though
which will tend to keep the overall rainfall potential a bit more
limited.

Rainfall rates with the stronger and more organized storms, and
especially the supercell activity closer to the central Gulf
Coast, will still be capable of reaching 1.5 to 2.5 inches/hour.
For areas that do see cell-training, some additional rainfall
amounts of 2 to 4 inches will be possible overnight. This may
drive at least some pockets of flash flooding and especially
around the more sensitive urban corridors.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!66qJBdcM3qSWnWivv0F8k5hcl4Ewq1Kk7lTRWu4iMEUXLiuVSl6OCxLGAI7I6L6dgqMn= -S6pPSdzuszfomkmTBntI2U$ for graphic product...

ATTN...WFO...BMX...HUN...JAN...LCH...LIX...MEG...MOB...OHX...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 35668714 35168590 33308571 31228642 30218757=20
29908868 29528996 29249100 29469199 30089196=20
30999050 32408972 34238929 35248854=20

=3D =3D =3D
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AWUS01 KWNH 290426
FFGMPD
CAZ000-ORZ000-291625-

Mesoscale Precipitation Discussion 1204
NWS Weather Prediction Center College Park MD
1125 PM EST Sat Dec 28 2024

Areas affected...Southwest OR...Northern CA

Concerning...Heavy rainfall...Flash flooding possible

Valid 290425Z - 291625Z

SUMMARY...Increasing rainfall rates associated with strengthening
atmospheric river activity will be impacting southwest OR and
northern CA overnight and through early Sunday morning. The wet
antecedent conditions and additional rains will promote concerns
for urban and small stream flooding, including a low-end flash
flood threat for any sensitive burn scar locations.

DISCUSSION...The latest surface analysis shows a warm front across
northern CA and with an offshore extension of this to a developing
surface low near 43N 130W. A cold front then extends well
southwest away from the low center. The low center will be
deepening overnight as it lifts northeastward toward the Pacific
Northwest overnight in conjunction with an amplifying shortwave
trough. The attendant warm front will slowly lift north with time,
but this coupled with deep layer southwest flow should still help
to focus a well-defined atmospheric river into the coastal ranges
of southwest OR and northwest CA.

GOES-W GeoColor satellite imagery shows the southwest extension of
moisture offshore of the West Coast, and the latest CMORPH2 and
NESDIS Blended Rain Rate data shows a pool of heavier rainfall
rates kust offshore in association with the advance of stronger
low to mid-level IVT magnitudes. The IVT values should increase to
750 to 1000 kg/ms/s in the 06Z to 12Z time frame across portions
of Coos, Curry, Del Norte and Humboldt Counties going from north
to south across southwest OR and northwest CA as the core of the
strong low to mid-level flow arrives ahead of the offshore cold
front and the south side of the aforementioned low center.

Enhanced warm air advection, moisture transport and orographic
ascent should favor rainfall rates increase to as much as 0.5" to
1.0"/hour across these coastal ranges. Rainfall rates may also
approach and briefly exceed a 0.50"/hour for some of the adjacent
terrain and counties extending inland into southern parts of the
OR Cascades and also down into the Shasta/Sisikiyou ranges of
northern CA including also eventually parts of the northern Sierra
Nevada early Sunday morning. Some of the heaviest overall rates
should tend to be associated with the final arrival and passage of
a cold front, and there may be some convective elements associated
with the front that will enhance the rainfall rates.

After the cold front passes through, the rates will then quickly
slacken, but additional rainfall totals over the next 6 to 12
hours are forecast to reach as high as 3 to 6+ inches for the
favored coastal ranges, and with as much as 1 to 3 inches
elsewhere. Some of these heavier rains may also reach down the
coast into the Bay Area Sunday morning.

Given the wet antecedent conditions and high streamflows, these
additional rains are likely to increase the concern for areas of
urban and small stream flooding, and there may be at least a
localized flash flood threat should some of these heavier rainfall
rates overlap any of the more sensitive burn scar locations.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8dOWZUGZOi6H9JYNkcqb2e7NJkXCb7ced17aC56rmajOFfoUdP0hiVS36up0JBynBsbt= KlEz6OyACTuHTemwR1GXNhc$ for graphic product...

ATTN...WFO...EKA...MFR...MTR...PDT...PQR...REV...STO...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 44712205 44262132 43742131 43252177 42792210=20
42532272 42132301 41792271 41522238 41502185=20
41262169 41012151 40382131 39562038 39022023=20
38822057 39092111 39682161 40372216 40452237=20
40322278 39782256 39342255 38702206 38012172=20
37282169 36972215 37352271 38142330 39372423=20
40592459 41602465 42482464 43212459 43962399=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 291535
FFGMPD
FLZ000-291945-

Mesoscale Precipitation Discussion 1205
NWS Weather Prediction Center College Park MD
1034 AM EST Sun Dec 29 2024

Areas affected...FL Keys

Concerning...Heavy rainfall...Flash flooding possible

Valid 291533Z - 291945Z

SUMMARY...There is increasing potential for torrential rainfall to
impact the FL Keys over the next few hours. Rainfall rates of 2 to
4 in/hr will be possible, though significant uncertainty remains
with the evolution of rainfall.

DISCUSSION...15Z visible satellite and local radar imagery from
KBYX showed a WSW to ENE axis of thunderstorms about 10 miles
north of the lower and middle FL Keys. The storms were slow
moving, located along a long-lived outflow boundary which has been
slowly dropping south over the past few hours. The environment was
favorable for organized cells with 40+ kt effective bulk shear and
500-1000 J/kg MLCAPE and about 2 inches PWAT (SPC mesoanalysis and
12Z KEY sounding). KBYX estimated rainfall rates were 2-4 in/hr
across the offshore waters of FL Bay. Area surface observations
along the Keys showed southerly winds of 10-20 kt with gusts to
near 30 kt, within a broadly confluent low level wind pattern just
above the surface, allowing overrunning of the slow moving outflow
boundary with cells generally training from west to east. There
were embedded mesocyclones with a fairly large mesocyclone/mesolow
located about 15 miles northwest of MTH. Upper level flow was
diffluent ahead of a southern stream upper jet max over the Gulf
of Mexico.

While hires models are unable to handle the mesoscale details of
the ongoing convective axis, loops of satellite/radar suggest the
outflow will continue to slowly sink south with heavy rain
impacting the Keys over the next 1-2 hours. Cyclonic flow around
the mesolow northwest of MTH may cause the outflow to
progressively sink south through the lower Keys over the next
couple of hours, with only a glancing blow of heavy rain to land
areas. However, this scenario is only speculation and continued
upstream convective development and strong southerly flow may
offset any stronger southward push of outflow, allowing for
stalling and torrential rainfall to persist a bit longer. Even if
rainfall overlaps the island chain for "only" an hour or two, that
could still result in several inches of rain which may produce
flash flooding.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4oDjM0fuHCSNj41GNcQFnIb3blAd1UEH4n_WyjmZbN8Ui77WR-eRpPF4Z7D5bG_NrfFP= a0rlnDyna1OEd9MAtfaPTas$ for graphic product...

ATTN...WFO...KEY...

ATTN...RFC...SERFC...NWC...

LAT...LON 25258024 24738027 24338119 24408180 24688195=20
24878117=20

=3D =3D =3D
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AWUS01 KWNH 092155
FFGMPD
TXZ000-100400-

Mesoscale Precipitation Discussion 0001
NWS Weather Prediction Center College Park MD
454 PM EST Thu Jan 09 2025

Areas affected...Upper Texas Coast

Concerning...Heavy rainfall...Flash flooding possible

Valid 092200Z - 100400Z

SUMMARY...Blossoming convection may briefly train along portions
of the Upper Texas coast this evening. Rainfall rates around
1.5"/hr are possible in urbanized communities and could lead to
localized flash flooding in poor drainage areas.

DISCUSSION...Deepening low pressure along the Texas coast is
located beneath the divergent right-entrance region of a robust
~160kt 250mb jet streak over the Middle Mississippi River Valley
this afternoon. Farther west, an anomalous upper trough over
northern Mexico contains 500mb heights as low as the 1st
climatological percentile according the NAEFS. Onshore flow will
increase at low levels this evening as high pressure over the Ohio
Valley and the deepening surface low along the Texas Coast tighten
the surface pressure gradient. In fact, southerly 850mb winds of
40-50kts around 00Z this evening are above the 99.5 climatological
percentile per NAEFS. These atmospheric parameters are playing a
role in the development of an IVT surpassing 1,000 kg/m/s, which
are values above the maximum observed IVT levels in the CFSR
database per NAEFS.

As the low-level wind field strengthens, surface-925mb FGEN will
also strengthen as low-level winds draw PWs up to 1.75" ahead of
the storm. Rainfall rates will increase in intensity this evening
to the north of the warm front, as well as the western flank of
the storm's circulation. Area averaged HRRR soundings from the
Houston metroplex to Galveston show >98% saturated soundings from
the surface to 300mb and warm cloud layers as deep as 12,000ft.
This supports favorable warm rainfall processes, but the one big
ingredient that is lacking is instability. Moisture advection and synoptic-to-mesoscale forcing alone would support hourly rainfall
rates of 1"/hr rainfall rates, but the HRRR shows as much as 250
J/kg of MUCAPE present along the Upper Texas coast. It is here
where hourly rainfall rates may approach 1.5"/hr with low chances
(5-10% via the 12Z HREF) for rainfall rates of >2"/hr.

NASA SPoRT-LIS in the sfc-10cm and sfc-40cm soil depths are
running drier than normal with some locations in moderate drought
according to the latest drought monitor. This atmospheric setup is
one where most of the observed rainfall will be more beneficial
than harmful. That said, locally excessive rainfall rates may lead
to localized flash flooding tonight in areas that feature a
greater concentration of non-permeable surfaces. Any minor
flooding or ponding may also be harder to identify for motorists
with the heaviest rainfall rates arriving after sundown.

Mullinax

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6WuwYvpJCKhEATb070Liy1Kuaz0SAUjCpSHY6BLIYNSZFUo__rWPTiO-Q7PN2edyhkNT= Rl3AkQy2cmPVUwEZCbtSnw0$ for graphic product...

ATTN...WFO...HGX...LCH...

ATTN...RFC...WGRFC...NWC...

LAT...LON 29949414 29599410 29139464 28519559 28559607=20
28819626 29089625 29489589 29849525=20

=3D =3D =3D
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AWUS01 KWNH 130529
FFGMPD
ALZ000-MSZ000-LAZ000-131027-

Mesoscale Precipitation Discussion 0002
NWS Weather Prediction Center College Park MD
1228 AM EST Mon Jan 13 2025

Areas affected...southeastern Louisiana into southern Mississippi
and southwestern Alabama

Concerning...Heavy rainfall...Flash flooding possible

Valid 130527Z - 131027Z

Summary...Isolated/low-end flash flood potential exists as shallow
convection continues to redevelop/train across the discussion
area.=20

Discussion...Over the past 2-4 hours, a focused area of convection
has trained along an axis extending from near Morgan City to near
Laplace and Lake Pontchartrain. The convection is favorably
oriented parallel to fast (60-80 kt) southwesterly flow aloft and
is also being maintained by focused convergence on the nose of
30-kt 850mb flow. Stout convergence is maintaining this
convection despite modest instability. Training convection was
resulting in a few spots of 0.5-1 inch/hr rain rates that have
persisted long enough for MRMS rainfall estimates exceeding 3
inches per six-hours. MRMS also depicts peak rainfall/FFG ratios
now exceeding 0.6 in spots beneath the training band.

Also somewhat concerning is the fact that models/CAMs suggest that
the sustained convergence resulting in the convection should
persist across areas west of New Orleans for at least another
couple hours, further contributing to localized runoff/flood
potential especially in western suburbs of New Orleans Metro.=20
Over time, the axis of heavier rainfall should translate eastward
in tandem with peak 850mb flow, with a few spots of isolated
flood/runoff problems extending toward Northshore Lake
Pontchartrain and adjacent areas of southern
Mississippi/southwestern Alabama over the next 2-4 hours or so.=20
This threat should remain isolated, but may become enhanced where
heavier rain rates can affect any urban/low-lying areas.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5lgj6_24p6wF6tyyVzp9KfTlxr-vAa1kZJ22IwlhC8WBE9JViKvc4uF2BemgDzRy8QhS= QRgbkMFzgMA3Zc4jIei9jZs$ for graphic product...

ATTN...WFO...JAN...LCH...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 31418904 31418809 30988783 30648822 30028936=20
29888975 29659086 29649184 30129186 30689116=20
31089015=20

=3D =3D =3D
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AWUS01 KWNH 261906
FFGMPD
CAZ000-270105-

Mesoscale Precipitation Discussion 0003
NWS Weather Prediction Center College Park MD
205 PM EST Sun Jan 26 2025

Areas affected...Southern California

Concerning...Heavy rainfall...Flash flooding possible

Valid 261905Z - 270105Z

SUMMARY...Locally heavy showers and a few thunderstorms arriving
over the next several hours may result in localized areas of burn
scar flash flooding, including debris flow activity. This will
include the Eaton, Palisades, Hurst, Franklin, Bridge and Hughes
fire areas.

DISCUSSION...GOES-W satellite imagery shows an upper-level low
continuing to drop south toward southern CA, with coastal surface
low pressure helping to facilitate an increase in low-level
onshore flow into the Transverse and Peninsular Ranges. The flow
is modest, but the uptick in Pacific moisture coupled with
gradually steepening mid-level lapse rates and divergent flow
aloft via DPVA is driving broken coverage of moderate to locally
heavy shower activity.

Additional shortwave energy rounding the base of the upper low
will overspread the coastal ranges this afternoon, including much
of the broader Los Angeles Basin. This coupled with a slight
increase in diurnally driven instability and orographic ascent
should help facilitate an increase in rainfall rates. In fact,
there has already been some lightning activity noted with recent
low-topped convection that has impacted Ventura County, and radar
imagery shows convection tending to intensify just offshore of Los
Angeles County which will be moving inland soon. This is where
some MUCAPE values of 250+ J/kg are noted in the latest RAP
analysis.

The 12Z HREF guidance favors occasional rainfall rates locally
reaching or exceeding a 0.25"/hour with some of the stronger
convective elements that materialize over the next several hours.
However, with the slight increase in instability and pulse nature
of the convective threat, it is possible that there could be as
much as a 0.25" of rain in as little as 15 to 30 minutes. The
latest guidance suggests some spotty 6-hour rainfall totals
reaching upwards of 1 inch where some of this activity persists
over the foothills of the terrain including the San Gabriel and
San Bernadino Mountains.

Given the significant sensitivities on the ground with the ongoing
wildfire activity and/or recently burned areas, these rains may be
sufficiently heavy enough, at least on a localized basis, to
result in some debris flow/mudslide activity and related flash
flooding concerns. The Eaton, Palisades, Hurst, Franklin, Bridge
and Hughes burn scar areas in particular will need to be closely
monitored for impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!53YZ0QmbT34wxoA1C2YMl_sXNG14x0HdATKan4Qquj7yxKUoUmHjETLGk1wc_3hwLdq4= tI_pP8L1bTMokH8WkTqy3os$ for graphic product...

ATTN...WFO...LOX...SGX...

ATTN...RFC...CNRFC...NWC...

LAT...LON 34861989 34761923 34681885 34521836 34381780=20
34271702 33761663 33271688 33101720 33241756=20
33491792 33601830 33841860 34041918 34291960=20
34422014 34662028=20

=3D =3D =3D
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AWUS01 KWNH 270206
FFGMPD
CAZ000-270805-

Mesoscale Precipitation Discussion 0004
NWS Weather Prediction Center College Park MD
906 PM EST Sun Jan 26 2025

Areas affected...Southern California

Concerning...Heavy rainfall...Flash flooding possible

Valid 270205Z - 270805Z

SUMMARY...An uptick in shower and thunderstorm activity is
expected through the evening hours across coastal portions of
southern California. This may result in localized areas of burn
scar flash flooding, including debris flow activity. This will
include the Eaton, Palisades, Hurst, Franklin, Bridge and Hughes
fire areas.

DISCUSSION...GOES-W satellite imagery continues to show a deep
layered low dropping south just off the southern CA coast. Some
cooling of cloud tops is noted over coastal Santa Barbara county,
resulting in a modest uptick in rainfall rates. As of 01z, water
vapor imagery continues to depict mid and upper level dry air
further south over Los Angeles county, likely helping limit shower
coverage and intensity. However, as the low continues to drop
south, we should see a gradual moistening of the column, along
with a steepening of lapse rates. These factors should promote an
uptick in shower (and isolated thunderstorm) activity over coastal
areas of Ventura, Los Angeles and Orange counties as the evening
progresses. In fact as of 02z just beginning to see an uptick in
shower activity and slight cooling in IR imagery over Los Angeles
County.

Recent HRRR runs and the 18z HREF are supportive of an uptick in
shower coverage and rainfall rates between 02z and 12z. HREF
probabilities of exceeding 0.5" in an hour increase into the
20-40% range. The 23z HRRR depicted hourly rainfall around 0.75"
just offshore, although the 00z HRRR is back closer to 0.5" an
hour for peak rates. Both the HREF and HRRR focus the majority of
these higher rates just offshore where the weak instability should
stay focused. However, while the better coverage of these higher
rates should remain just offshore, do anticipate we will see some
0.5"-0.6" an hour rainfall make it onshore on a localized basis
anytime between ~02z and 12z.

For the most part this forecast rainfall will only result in
localized minor flooding of urban and low lying areas. However,
more significant impacts are possible over recent burn scar areas,
particularly over Los Angeles County. Confidence on these more
significant impacts remains low, however with the expected uptick
in shower coverage and intensity this evening, the threat of
significant impacts is higher than it was earlier this afternoon.
The Eaton, Palisades, Hurst, Franklin, Bridge and Hughes burn scar
areas in particular will need to be closely monitored for debris
flow impacts this evening into the overnight hours.

Chenard

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4uDbQG2HQ3AXj8bza6JbxE_3NsjrpFL5VCim8O4HzhHqpTV4u8UDgWZJQs1a_ZIc2wmp= mkTgB9Us3LpwC15hDi3sH1k$ for graphic product...

ATTN...WFO...LOX...SGX...

ATTN...RFC...CNRFC...NWC...

LAT...LON 34651835 34431817 34301774 33981760 33631762=20
33451786 33571821 33631832 33991925 34322034=20
34382049 34642044 34551947 34561934 34611884=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 300146
FFGMPD
ARZ000-TXZ000-OKZ000-300644-

Mesoscale Precipitation Discussion 0005
NWS Weather Prediction Center College Park MD
845 PM EST Wed Jan 29 2025

Areas affected...Parts of North Texas and Southeast OKlahoma

Concerning...Heavy rainfall...Flash flooding possible

Valid 300144Z - 300644Z

SUMMARY...Increasing shower and thunderstorm activity is underway
and is expected to continue into the late evening across portions
of northern Texas and southeast Oklahoma which results in an
increasing risk of flash flooding through 0630Z.

DISCUSSION...Composite image of area 88D reflectivites from early
this evening showed shower and thunderstormn activity growing in
areal coverage with embedded heavy rainfall already moving through
portions of the urbanized Dallas-Ft Worth metropolitan area.=20
Given the approach of a trough in the southern stream along with a
surface cold front...the trend for increasing coverage and
rainfall intensity is expected to continue through at least 0630Z
leading to increased risk of flash flooding.

Recent HRRR runs and the 18z HREF are supportive of increasing
coverage of showers and thunderstorms overnight as low level flow
becomes southerly in the 20 to 35 kt range and begins to draw
moisture northward from the Gulf. However...the models have
already been proven to be too slow to develop heavy rainfall
rates. Rainfall rates from the most active convection should
generally be in the 1 to 1.5 inch range although isolated 2 inch
per hour rates can not be entirely ruled out with some potential
for 2 to 4 inches possible.

Concern for flash flooding is greatest in urban areas and where
storms have a chance to train...with flooding more in low lying
areas in more rural areas.

Bann

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6RSuJnuptgV9-xdqjF6cijpCseCo3G956WMpp8TGA3eVxuaKhKWo-mAMwAdeG9yIQKOc= gagUSGQqnwQfU5ZP1VZ0RrY$ for graphic product...

ATTN...WFO...EWX...FWD...LZK...OUN...SHV...SJT...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 35289442 34329402 32469591 31239713 30439775=20
30989861 32489814 34389658=20

=3D =3D =3D
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AWUS01 KWNH 300544
FFGMPD
TXZ000-OKZ000-301043-

Mesoscale Precipitation Discussion 0006
NWS Weather Prediction Center College Park MD
1243 AM EST Thu Jan 30 2025

Areas affected...North-Central to Northeast TX...Far Southeast OK

Concerning...Heavy rainfall...Flash flooding likely

Valid 300543Z - 301043Z

SUMMARY...Heavy showers and thunderstorms will continue through
the overnight hours. Areas of cell-training will continue to pose
concerns for flash flooding and especially around the more
urbanized locations. This will include the Dallas-Fort Worth
metropolitan area.

DISCUSSION...The latest GOES-E IR satellite imagery in conjunction
with dual-pol radar shows a southwest/northeast oriented band of
heavy showers and thunderstorms impacting areas of north-central
to northeast TX, including especially the southern and eastern
portions of the Dallas-Fort Worth (DFW) metropolitan area.

All of the convection is being driven by the interaction of
shortwave energy ejecting northeast across the southern Plains out
ahead of the deep closed low over the Southwest, and with the
pooling of at least modest instability and favorable southerly
moisture transport out ahead of a frontal zone. MUCAPE values
across much of central to northeast TX have risen to as much as
1000 J/kg with the aid of a southerly low-level jet of 30 to 40+
kts, and the CIRA-LVT values in the SFC-850 mb layer have been
increasing steadily over the last few hours which is reflective of
the increasing low-level moisture transport.

The flow aloft is quite divergent based off the GOES-E IR/WV data
and this should continue to promote a stronger low-level jet
response going through the overnight hours with enhanced warm air
advection along with favorable moisture and instability transport
for heavy rainfall. There has been some cell-training noted with
the convection over the last couple of hours and portions of the
DFW metroplex have already received 2 to 3+ inches of rain with
rainfall rates with some of the stronger cells reaching 1.5+
inches/hour.

Over the next few hours, the focus for the strongest axis of
convection and heavy rainfall should tend to remain over the
southern and eastern sides of the broader DFW metroplex, with some
localized expansion of convection expected off to the northeast
toward areas of the Arklatex, but mainly concentrated over areas
of northeast TX and far southeast OK.

Additional rainfall amounts of 2 to 4 inches are forecast
overnight with isolated heavier totals possible where any
cell-training tends to persist. Given the heavy rainfall that has
already occurred over the last few hours, and these additional
totals, flash flooding is likely overnight with the more urban
locations the most susceptible to impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7Uv1FVTO6kNQSACLqRdyU4m03fCcfknashKVouQS9FXbudzYYCfAIwO3RmYkc5y8sR8q= 4dSTJ9xm3Jq-hVo_-dioFDs$ for graphic product...

ATTN...WFO...FWD...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 33999460 33289472 32549572 31759694 31499786=20
31699820 32269791 33179691 33949544=20

=3D =3D =3D
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AWUS01 KWNH 300922
FFGMPD
ARZ000-TXZ000-OKZ000-301520-

Mesoscale Precipitation Discussion 0007
NWS Weather Prediction Center College Park MD
421 AM EST Thu Jan 30 2025

Areas affected...Central to Northeast TX...Southeast OK...Western
and Central AR

Concerning...Heavy rainfall...Flash flooding likely

Valid 300920Z - 301520Z

SUMMARY...The threat for areas of flash flooding will continue
this morning from broken bands of heavy showers and thunderstorms
which will occasionally be capable of training over the same area.

DISCUSSION...The latest GOES-E IR satellite imagery along with
dual-pol radar continues to show broken areas of heavy shower and
thunderstorm activity impacting areas of central to northeast TX
through southeast OK and more recently into areas of western AR.

Strong warm air advection with the aid of a strengthening
south-southwest low-level jet of 30 to 50 kts continues to work in
tandem with modest instability, but rather strong moisture
convergence for sustainable convection. The flow aloft remains
rather divergent out ahead of a deeper layer low center slowly
ejecting east out into the southern High Plains, and this along
with a triple point low center over northern TX is further helping
to concentrate a corridor of rather strong forcing.

MUCAPE values remain generally around 1000 J/kg with PWs close to
1.5 inches, and this coupled with at least moderate shear should
continue to support some rainfall rates with the stronger storms
reaching as high as 1.5 inches/hour. This has been realized over
much of the DFW metroplex already where cell-training overnight
has yielded rainfall totals of as much as 2 to 5 inches.

As shortwave energy ejects off to the northeast across the
Arklatex region this morning, the overall axis of stronger warm
air advection and moisture transport should also translate off to
the northeast. This will help to maintain locally heavy showers
and thunderstorms along an axis that will still tend to linger
over northeast TX and southeast OK, but should move well
downstream into areas of western and central AR going through the
morning hours.

Given the locally heavy rainfall rates and periodic cell-training
concerns, additional rainfall totals of as much as 2 to 4 inches
are expected which is also supported by the 00Z HREF guidance and
recent HRRR runs. Some of these rains will be falling over areas
that have already seen locally heavy rainfall overnight, so
additional areas of flash flooding will generally be likely this
morning and especially over the more urbanized areas.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5ZQehYyNkVq3vDFLKDg74s0Azc8Jcq8SamPVbRiiYZI4a181TMTI4Rg1VcBklN6Hxhh9= u-kRalLjnzNhSWDyCxIcasw$ for graphic product...

ATTN...WFO...FWD...LZK...MEG...OUN...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 36009200 35839128 35319103 34489198 33439396=20
32349544 31579663 31269764 31619826 32429817=20
33229756 34439598 35469410 35849292=20

=3D =3D =3D
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AWUS01 KWNH 301534
FFGMPD
TNZ000-KYZ000-ILZ000-MSZ000-MOZ000-ARZ000-TXZ000-OKZ000-302130-

Mesoscale Precipitation Discussion 0008
NWS Weather Prediction Center College Park MD
1033 AM EST Thu Jan 30 2025

Areas affected...ArkLaTex into mid-MS Valley

Concerning...Heavy rainfall...Flash flooding likely

Valid 301532Z - 302130Z

SUMMARY...Areas of flash flooding appear likely to continue from
portions of the ArkLaTex into the mid-MS Valley through 21Z. Flash
flood coverage is expected to be scattered with peak rainfall
rates of 1-2 in/hr and additional totals of 2-4 inches are likely
over the next 6 hours.

DISCUSSION...Widespread areas of moderate to heavy rainfall were
ongoing as of 15Z across northeastern TX into central AR and the
MO Bootheel. While peak rainfall rates over the past few hours
have dropped below 1 in/hr, the steady rainfall over the region
since just before midnight has resulted in 3 to 5 inches of
observed rainfall from northeastern TX into the Ouachita Mountains
and the I-40 corridor. A strong low level jet was present from the
ArkLaTex into western AR with VAD wind plot observed speeds of
50-60 kt. Low level warm air advection to the north of a surface
warm front (which extended W to E across southern AR) was focusing
repeating rounds of moderate to heavy rain from SW to NE along an
elevated convergence axis which was located between 925-850 mb
from northeastern TX into the northwestern half of AR.

While elevated instability to the north of the warm front was, and
is expected to remain, weak (<500 J/kg) through the early
afternoon, steady rain with rates occasionally peaking above 1
in/hr should maintain areas of flash flooding from portions of the
ArkLaTex into the mid-MS Valley over the next 3-6 hours. As a
powerful closed low over the southern/central High Plains
continues to slowly advance eastward during the afternoon, the low
level jet is forecast to maintain its intensity while gradually
translating eastward. Diffluent flow aloft and the slow moving to
nearly stationary elevated axis of convergence will continue to
allow for repeating rounds of heavy rain with occasional rates of
1+ in/hr (but less than 2 in/hr) where pockets of relatively
higher instability coincide with training echoes of heavy rain.
Additional rainfall of 2-4 inches can be expected from portions of
southwestern AR into northeastern AR and the adjacent MS Valley.
Due to fairly low flash flood guidance values, flash flooding is
considered likely.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6pDT3mKLeC3Lx-xR0A--qt9EQ6LYvz1vztxsgzxRgcoq9N1K6r0u4rlXBtPHZyUI6B5P= efYtnkAJhPWWh_oplYOSad0$ for graphic product...

ATTN...WFO...FWD...LSX...LZK...MEG...OHX...PAH...SGF...SHV...
TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...OHRFC...NWC...

LAT...LON 37388967 37298861 37068807 36648778 36248786=20
35598849 34619099 33649280 33179405 33249540=20
34009560 35969379 37079202=20

=3D =3D =3D
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AWUS01 KWNH 302203
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-310200-

Mesoscale Precipitation Discussion 0009
NWS Weather Prediction Center College Park MD
502 PM EST Thu Jan 30 2025

Areas affected...mid-MS Valley into lower/middle OH Valley

Concerning...Heavy rainfall...Flash flooding possible

Valid 302200Z - 310200Z

SUMMARY...Areas of moderate to heavy rain will maintain a flash
flood threat from northeastern AR/southeastern MO into the lower
and middle OH Valleys and much of western and central KY through
at least 02Z. Hourly rainfall of 0.5 to 1.0 inches will be
possible along with 3 hourly rainfall up to 2 inches.

DISCUSSION...A broad area of moderate to heavy rainfall extended
from near the MO Bootheel into the lower OH Valley as of 2130Z.
This area of rainfall has been translating northeastward during
the day and has been responsible for peak hourly rainfall up to
about 1 inch from the eastern AR/MO border into western KY and
northwestern TN since ~18Z. While hourly rainfall totals have not
been too high given MUCAPE has largely remained below 500 J/kg,
3-hour rainfall totals of 2 to 3+ inches have resulted in numerous
reports of flooding and flash flooding from southwestern to
northeastern AR.

The heaviest rainfall has been occurring at the nose of a 50-60 kt
low level jet measured between 925-850 mb, which has been
overrunning a surface warm front lifting north across AR and
northern MS. The axis of greatest low level moisture transport is
likely to continue to slowly shift east into KY/TN over the next
few hours with an elevated convergence axis aloft focusing from
near the MO Bootheel into the lower OH Valley. The orientation of
this low level convergence axis will be parallel to the mean
steering flow, allowing for repeating rounds of moderate to heavy
rain.

While instability is likely to remain limited into the late
evening/early overnight hours, forcing will remain strong in the
form of low level warm air advection and convergence beneath a
strengthening area of upper level divergence located within the
right-entrance region of a 150-160 kt upper level jet max centered
over OH/PA/NY. Peak hourly rainfall of 0.5 to 1.0 inches and
3-hourly rainfall of 1-2 inches may result in additional flash
flood concerns across downstream locations along the OH Valley as
these rains fall on top of locations that have already picked up 2
to 3+ inches of rain since this morning. Embedded within this
threat could be an isolated spot or two with higher end
runoff/flooding depending on local hydrologic conditions.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_WfeXhkUoEcRdU2jQCUfJEVb89Eaqg1ZGQYuJA1_DpAdmS-upWdTLbPLYGO5d1LDBdZx= HPDxtoLrEc-3uVEsyc_L5_A$ for graphic product...

ATTN...WFO...ILN...ILX...IND...JKL...LMK...LSX...LZK...MEG...
OHX...PAH...

ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC...

LAT...LON 38848597 38598485 38008385 37228401 36768481=20
36528671 36118840 35438943 35109024 35369091=20
36259103 37329028 38618767=20

=3D =3D =3D
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AWUS01 KWNH 310202
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MSZ000-MOZ000-ARZ000-310600-

Mesoscale Precipitation Discussion 0010
NWS Weather Prediction Center College Park MD
901 PM EST Thu Jan 30 2025

Areas affected...Portions of Kentucky and Tennessee

Concerning...Heavy rainfall...Flash flooding possible

Valid 310200Z - 310600Z

SUMMARY...Areas of moderate to heavy rain will maintain a flash
flood threat across portions of the lower and middle OH Valleys
and much of KY through at least 06Z. Hourly rainfall of 0.5 to 1.0
inches will be possible along with 3 hourly rainfall up to 2
inches.

DISCUSSION...A broad area of moderate to heavy rainfall extended
along and east of the Mississippi River into the Ohio and
Tennessee Valley as of 0145Z. This area of rainfall has been
translating northeastward during the afternoon and early evening
and has been responsible for peak hourly rainfall up to about 0.75
inch in eastern AR/MO border into western KY. MUCAPE has largely
remained below 500 J/kg but that was enough to support 3-hour
rainfall totals of 1.5 to 3 inches earlier.

The heaviest rainfall has been occurring at the nose of a 50-60 kt
low level jet measured between 925-850 mb, which has been
overrunning a surface warm front lifting north across northeast
Arkansas and far southern Tennessee at 00Z. The axis of greatest
low level moisture transport is likely to continue to slowly shift
east into KY/TN through late evening with an elevated convergence
axis aloft focusing activity into the western lower OH Valley. The
orientation of this low level convergence axis will be parallel to
the mean steering flow, allowing for repeating rounds of moderate
to heavy rain.

While instability is likely to remain limited into the late
evening/early overnight hours, forcing will remain strong in the
form of low level warm air advection and convergence beneath a
strengthening area of upper level divergence located within the
right-entrance region of a 135-150 kt upper level jet max centered
over OH/PA/NY from 00Z soundings. Peak hourly rainfall of 0.5 to
1.0 inches and 3-hourly rainfall of 1-2 inches may result in
additional flash flood concerns across downstream locations along
the OH Valley...with the greatest concern for excessive rainfall
at locations where these rains fall on top of locations that have
already picked up 2 to 3+ inches of rain since this morning.
Embedded within this threat could be an isolated spot or two with
higher end runoff/flooding depending on local hydrologic
conditions.

Bann

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6AZrqa0rA0VEncquGN1STgxmYga5xVTkj-dm30YilLetOxvMSuYZwHR0OkwE17w4VfiI= Yziu9BoDUX_K83OjKn28WP0$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...MEG...OHX...PAH...RLX...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38658585 38458319 37408284 36798460 35488777=20
34838867 34818982 35518999 37188904 38108772=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 011917
FFGMPD
CAZ000-020700-

Mesoscale Precipitation Discussion 0011
NWS Weather Prediction Center College Park MD
217 PM EST Sat Feb 01 2025

Areas affected...central to northern California

Concerning...Heavy rainfall

Valid 011915Z - 020700Z

SUMMARY...Heavy rain will develop across north-central CA this
afternoon and especially tonight. Rainfall will be steady but with
hourly totals increasing to over 0.5 inches, especially for the
northern Sierra Nevada tonight. 12 hour totals of 3 to 6+ inches
can be expected for the northern Sierra Nevada with 1 to 3 inches
for the Coastal Ranges.

DISCUSSION...A big picture view of Blended Total Precipitable
Water (PW) and MIMIC Total PW showed a southwest to northeast
oriented axis of PW values in excess of 1.5 inches streaming
across HI to about 36N, and extending east to about 127W,
weakening with eastward extent to the West Coast. Land-based GPS
data from 18Z showed that PW values of greater than 1 inch
extended from northern Mendocino County to Santa Barbara County
with a max near 1.25 inches centered around San Francisco Bay and
eastward into the lower Sacramento River Valley. The values within
the core of the moisture axis are well over 200 percent of normal
via the blended imagery.

Placement of a low ot mid-level low over British Columbia and
ridge centered about 600 miles west of the northern Baja Peninsula
has allowed for a funneling of these anomalous moisture values
into the CA coast. A powerful (191 kt at 250mb via 12Z SLE
sounding) zonally oriented upper level jet was sandwiched between
the low to the north and high to the south, with no significant
movement of these two features forecast through early tonight.
Recent GFS, RAP and other guidance are good agreement with the
arrival of a corridor of stronger 850 mb winds (40-50 kt) arriving
into Sonoma and Marin counties over the next 1-2 hours, oriented
perpendicular to the coastline along and just south of a east-west
oriented quasi-stationary front extending offshore of the central
CA coast. Some backing of low level flow toward the southwest is
expected across the Valley into the foothills of the Sierra
Nevada. With the increase in low level flow and a subtle increase
in PW values (up to ~1.4 inches), IVT magnitude is expected to
peak between 800-900 kg/m/s from just north of San Francisco Bay
into the southern Sacramento Valley in the 21Z-02Z time frame. The
surge will be short-lived however and poor low and mid level lapse
rates should limit instability to near zero for coastal and inland
locations through the first half of tonight with rainfall
intensity largely driven by wind speed and orographic lift.

Steady light to moderate rain was ongoing across the coast and
Sierra Nevada of north-central CA as of 18Z but should increase in
magnitude over the next 6 hours, especially into the upslope
regions of the Sierra Nevada where orographic ascent will be
maximized given 700 mb winds peaking in the 70-80 kt range just
after 00Z. 12 hour rainfall totals of 1 to 3 inches are expected
for the Coastal Ranges from just north of San Francisco Bay to
just south of 40N and 3 to 6+ inches for the Sierra Nevada from
roughly Amador to Butte counties. While rainfall through 07Z is
not expected to produce impacts from flooding, heavy rain will
continue through the night with potential for flooding and higher
rain rates to increase prior to 12Z.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5dIiGAeulu1rxK0zydcPEuCyMtNZXnx8os26hae-z-rkAXFPgV4aUFw3fciXn_7RGhfq= v6P58ylRb53IJTNahh-6NHU$ for graphic product...

ATTN...WFO...EKA...HNX...MTR...REV...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 40442163 40302137 40112102 39882047 39442017=20
38772012 38181972 37901960 37541946 37371955=20
37521991 37722010 38022037 38332090 38262158=20
37982207 37892261 37972305 38372341 38722374=20
39002387 39362397 39652383 40062346 40262297=20
40412231=20

=3D =3D =3D
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AWUS01 KWNH 020701
FFGMPD
NVZ000-CAZ000-021900-

Mesoscale Precipitation Discussion 0012
NWS Weather Prediction Center College Park MD
200 AM EST Sun Feb 02 2025

Areas affected...Northern California

Concerning...Heavy rainfall

Valid 020700Z - 021900Z

SUMMARY...An atmospheric river aimed at northern California will
continue to produce heavy rain with rates between 1/4 and 3/4
inches per hour possible.

DISCUSSION...An atmospheric river aimed at northern California
will continue to advect tropical moisture from near Hawaii
northeastward into the state today. The moisture has a tropical
connection due to an expansive area of high pressure located off
southern California joining forces with a cold core low off
Vancouver Island to squeeze the moisture into a relatively narrow
corridor (atmospheric river). PWATs between 1 and 1.25 inches are
associated with the moisture plume. This is 4 sigma above the
climatological normal as well as within the 90th to 95th
percentile compared to a 30-year average of PWATs for the area.
IVT values from CW3E GFS and EC guidance are around 800 kg/ms.
Over the past 24 hours, Anywhere from 1 to 4 inches of rain have
fallen across northern California, with the highest values in the
Sierras around and west of the Lake Tahoe region. NASA Sport soil
moisture imagery shows much of the surface soil layer has
saturated significantly compared to 24 hours ago, so most of the
rain that falls from here should convert to runoff.

Radar imagery shows a plume of rainfall occurring over much of far
northern California with rates generally between 1/10 and 1/4 inch
per hour ongoing. These rates are confirmed by the numerous
weather stations set up across northern California. A stationary
front draped over northern California (not shown) delineates the
remarkable surface convergence occurring within this atmospheric
river, with winds off the coast of Crescent City 20 kts out of the
north, and winds both off the coast of Mendocino as well as up the
northern Sacramento Valley are 20 kts out of the south. This
remarkable convergence is adding to the overall lift within the
atmosphere along the front, with almost all of the rain occurring
north of the front.

As a potent upper level shortwave approaches the coast over the
next 12 hours, HiRes models are in good agreement as to a slight
increase in rainfall rates in far northern California over the
next 4 hours or so, followed by a gradual southward drift of the
rainfall plume towards Point Arena and the northern Sacramento
Valley. Rainfall rates may locally increase to as high as 3/4
inches per hour. Along the coast, rates should diminish through
the predawn hours, with the rainfall tapering from north to south
through the morning. Expect 3-6 inches of rain for much of the
northern Sierras through 19Z, 2-4 inches of rain for the northern
Coastal Ranges, and lesser amounts within the Sacramento Valley
along the I-5 corridor and to the immediate lee (east) of the
coastal ranges.

Mudslides and rock slides are possible in the foothills and
mountains below 6,500 feet where the precipitation remains all
rain. Localized flooding is possible in the areas where the
heaviest rain occurs over flood-sensitive and low-lying areas.

Wegman

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5Y4MMwOjNyUN8M1ASjGdGoHdQd6EJBF4AQTmwo1AvwSuAu3qu99oohaY-xe_RHQ_mUMv= 9zgJEkNuqis28DNtP29-2pg$ for graphic product...

ATTN...WFO...EKA...MFR...MTR...REV...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41902181 41862023 41252007 39932011 39391980=20
38501957 38312007 38352115 39352158 40282212=20
40012270 39472270 38732243 38352235 38622251=20
38122328 38932398 39432394 40012417 40472452=20
40982421 41562316=20

=3D =3D =3D
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AWUS01 KWNH 021936
FFGMPD
CAZ000-030700-

Mesoscale Precipitation Discussion 0013
NWS Weather Prediction Center College Park MD
236 PM EST Sun Feb 02 2025

Areas affected...northern California

Concerning...Heavy rainfall

Valid 021935Z - 030700Z

SUMMARY...Moderate to Heavy rain will continue over the northern
Sierra Nevada throughout the next 6-12 hours while a second round
of moderate to locally heavy rain develops for the northern
Coastal Ranges this evening. While locally higher totals will be
possible on an isolated basis, additional rainfall totals of 3 to
5 inches are expected for the northern Sierra Nevada into the
southern Cascades and an additional 1 to 2 inches for the northern
Coastal Ranges through 07Z.

DISCUSSION...Eastern Pacific view of total precipitable water (PW)
showed a relatively narrow axis of values greater than 1 inch
extending from near the triple point of an occluded cyclone 36N
138W (which showed up well in visible satellite imagery), ENE to
the northern CA coast. Gauge observations have shown peak hourly
rainfall totals in the 18Z hour of 0.1 to 0.2 inches for the
northern Coastal Ranges and 0.25 to locally in excess of 0.5 in/hr
for the northern Sierra Nevada. 24 hour totals near 9 inches have
been reported just east of Chico in the Sierra Nevada with up to
roughly 4 inches for the northern Coastal Ranges. Reports of
flooding thus far have been limited and primarily focused across
southern portions of the region on either side of I-80 in the
Sierra Nevada and between San Pablo Bay and Santa Rosa via local
storm reports.

Confluent mid-level flow between a mid-level low over southwestern
Canada and a low amplitude longwave trough centered near 145W
along with a ridge over the Baja Peninsula will keep zonal flow
focused from the northern CA and OR coastline, eastward into the
central U.S. through the overnight. At the surface, a shallow but
well-defined stationary front, co-located with the moisture axis,
will essentially remain in the same place over the next 6-12 hours
(slow northward drift), with low level winds varying within the
plume between 40-50 kt in the 850-700 mb layer. Some subtle
strengthening of 850 mb winds will be possible toward 00Z ahead of
the leading edge of a weak mid-level shortwave expected to near
the West Coast at 00Z, but IVT values are forecast to remain in
the 400-600 kg/m/s range through 06Z Monday across northern CA.

No significant changes to peak rainfall rates are expected for
northern CA through 06Z, but additional light to moderate rainfall
(perhaps locally heavy) is expected into the northern Coastal
Ranges later this evening with the approach of the offshore
mid-level impulse. Additional peak rainfall totals of 1-2 inches
for the Coastal Ranges and 3-5 inches for the northern Sierra
Nevada are likely over the next 12 hours but given rainfall rates
will remain somewhat modest, it is the long duration of this
rainfall event that will be noteworthy. At least through 06Z
tonight, additional flooding impacts are expected to remain
isolated with rainfall rates remaining under more critical
thresholds.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4n3AZcPfTSdqmNWbK_ffJ6tUgbACVgJ7QSgoq4mOymxc8QfMd6TnHX7t1gN3EeZjfQhd= wbRivGG_nTd2zxNA-mPbQZ4$ for graphic product...

ATTN...WFO...EKA...MFR...MTR...REV...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41932111 41782055 41352037 41122043 40772058=20
40382047 39872026 39282015 38942034 38772068=20
38712095 38892118 39192143 39482163 39782182=20
40032213 40082244 39972271 39512264 39282247=20
38962222 38592215 38302216 38122234 38132269=20
38222311 38502358 38832386 39182406 39592417=20
40192451 40602421 40832377 40892338 40932300=20
41122267 41302234 41712170=20

=3D =3D =3D
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AWUS01 KWNH 022304
FFGMPD
CAZ000-030200-

Mesoscale Precipitation Discussion 0014
NWS Weather Prediction Center College Park MD
603 PM EST Sun Feb 02 2025

Areas affected...Shasta County / northern CA

Concerning...Heavy rainfall...Flash flooding likely

Valid 022302Z - 030200Z

SUMMARY...A narrow and focused band of heavy rain is expected to
result in a localized area of flash flooding for portions of
Shasta County in and around the Redding metro area. Peak hourly
rainfall of 1-2 inches will be possible with localized additional
totals of 3-5 inches through 02Z.

DISCUSSION...Local radar imagery from KBBX at 2240Z showed a
narrow band (just 2-4 miles wide) of stationary heavy rain
occurring just south of downtown Redding, CA. This band has been
present for the past 2 to 3 hours and has resulted in 4 to 6
inches of rain, most of which has occurred since 20Z. These
rainfall reports have been sourced from a number of
Wunderground.com observations with the band just recently shifting
south to Redding Regional Airport.

The band of heavy rain was located along an axis of strong
surface/near-surface convergence co-located with a
quasi-stationary front that extended SW to NE across the northern
Sacramento Valley. Weak instability may be present with RAP
estimates of near 100 J/kg. Little change to the pattern on the
regional scale is expected to keep the quasi-stationary front in
roughly the same position over the next few hours though some
minor wavering of the rainfall axis is expected over the next
couple of hours along with possible weakening of the little
instability that could be in place. Given the presence of this
band of heavy rain across the I-5 corridor near Redding and into
the higher terrain of eastern Shasta County, a localized area of
flash flooding appears likely with this band. Due to the highly
mesoscale nature of this feature, confidence is below average in
its longevity but it seems likely to persist for at least another
1-2 hours.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4FAue9RTzh4i5PUpyW3cLxsADkEMcSbETXUz06rF_bbTk_yK60JiUQSPa9-OGZO58C4g= VO04DZVPTarVWNVVISBa5BE$ for graphic product...

ATTN...WFO...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41082185 40972166 40772163 40642187 40262256=20
40462268 40972208=20

=3D =3D =3D
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AWUS01 KWNH 030213
FFGMPD
CAZ000-030700-

Mesoscale Precipitation Discussion 0015
NWS Weather Prediction Center College Park MD
913 PM EST Sun Feb 02 2025

Areas affected...Redding Area of Shasta County

Concerning...Heavy rainfall...Flash flooding possible

Valid 030212Z - 030700Z

SUMMARY...Heavy rain associated with a convergence band over
Shasta County, CA will continue into tonight. Flash flooding will
be possible in addition to the ongoing areal flooding.

DISCUSSION...An impressive WSW-ENE convergence band that set up at
the head of the Sacramento Valley near Redding and Anderson, CA
continues to be the source of heavy rain this evening. A strong
southerly low level jet (LLJ) with winds of over 40 kts at 850 mb
continues along the Sacramento Valley, with surface stations south
of the band reporting winds as high as 20 kts south of the band.
The band had been nearly stationary over Anderson, CA or just
south of Redding, but trends have been for the band to crawl
northward with time. Guidance shows very little if any
instability, so this band is likely being forced by the strong
convergence in the area from the combination of the strong
southerly flow with the LLJ hitting a stationary front in that
same area, as well as localized upslope as the terrain of the
Sacramento Valley forms an arc, or upside down U, allowing for
southerly flow to become focused and converge in the Redding area.
Surface observations show there has been over 1.7 inches of rain
in the last 3 hours, and 2.5 inches of rain in the last 6.

HiRes guidance is in good agreement that the front and convergence
band will remain in place for at least the next several hours, if
not throughout the overnight (HRRR). With rates as high as an inch
per hour possible, expect continued areal flooding and possible
flash flooding in those areas where the convergence band interacts
with the terrain to focus the rain water into narrow streams,
creeks, and channels. Urban areas in and around Redding may also
locally increase the flash flooding threat.

Wegman

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9eS4LoJC5rkLYwpzCDlGSmDkq3NN8Fuul9JOKPgas3J0LLhDLgP0FQpPCjCFg8iwYp73= zgSNm_NPyE4BnVj4BcMxRqs$ for graphic product...

ATTN...WFO...EKA...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 40792205 40692191 40492197 40422224 40402259=20
40332288 40452290 40542276 40662255 40742235=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 030703
FFGMPD
CAZ000-031900-

Mesoscale Precipitation Discussion 0016
NWS Weather Prediction Center College Park MD
202 AM EST Mon Feb 03 2025

Areas affected...Northern California

Concerning...Heavy rainfall...Flash flooding possible

Valid 030702Z - 031900Z

SUMMARY...Steady rain will continue into northern California today
with localized convergence bands of heavy rain embedded within the
broader atmospheric river. Localized rates over 1 inch per hour
and flash flooding possible.


DISCUSSION...Heavy rain associated with the ongoing atmospheric
river will continue through the day today. Just in the past 24
hours, rainfall amounts locally exceeding 6 inches have fallen
around and just south of the Redding area. This caused flooding in
several areas as noted by the local storm reports. For now the
band that caused that flooding around Redding has diminished in
intensity. However, many of the ingredients that led to the band's
formation remain in place. A stationary front remains in the area
acting as a convergence boundary between the colder air to its
north and the warmer air and southerly flow to its south. A
southerly low level jet from 850 to the surface remains strong
moving up the Sacramento Valley, with winds to 40 kts at 850 and
20 kts as noted by several stations in the Sacramento Valley south
of the area of rain. This low level jet and the orientation of the
terrain are locally enhancing convergence at the northern end of
the Sacramento Valley around Redding, as noted by localized
increased in the radar reflectivities around that area. Meanwhile,
plumes of moisture continue to move into the northern California
coast, where their initial uplift by the northern coastal ranges
are also responsible for heavier rains.

The jet stream remains largely zonal extending hundreds of miles
west out into the Pacific. The upper low to the north and the high
to the south continue to put the squeeze on the moisture plume,
increasing upper level winds and narrowing the moisture into a
100-200 mile wide corridor that is the atmospheric river. During
the day today, the upper low helping direct the jet stream will
retrograde west. This will begin to reorient the atmospheric river
from its current westerly flow to a southwesterly flow. This will
allow the atmospheric river to begin to drift southward down the
coast, while remaining in place over much of interior northern
California. This reorientation may also work to support the low
level jet, as the wind flow becomes more parallel with the
mountains.

HiRes guidance is in agreement that rainfall rates should remain
largely steady through the early morning, though again embedded
heavier bands remain very possible, especially at the northern end
of the Sacramento Valley. Where any bands form, localized flash
flooding in addition to the ongoing areal flooding cannot be ruled
out. A subtle surface low will approach the coast around 18Z,
likely enhancing the rainfall rates area-wide from west to east
and could cause additional flooding into the afternoon. Expect
another 2-4 inches of rain into the northern Sacramento Valley
through 19Z with 1-3 inches of rain expected elsewhere in the
highlighted area.

Wegman

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7nIjQKs2tSVxxpcQYGLU-voXabZlkuB003nbt11vwnS7sz9ePTpazwWKCbA1blSCz4CG= gVYQhD9XiSdz8mYMgIlR4qQ$ for graphic product...

ATTN...WFO...EKA...MFR...REV...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41912071 41622024 41282032 40912043 40342055=20
39872043 39302035 39182094 39862145 40172184=20
40302233 39802263 39442263 39162262 38912281=20
38832334 38902386 39432391 39712388 40082424=20
40392454 40732441 41102419 41622357 41882317=20
41852176=20

=3D =3D =3D
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AWUS01 KWNH 031757
FFGMPD
CAZ000-040600-

Mesoscale Precipitation Discussion 0017
NWS Weather Prediction Center College Park MD
1256 PM EST Mon Feb 03 2025

Areas affected...Northern California & San Francisco Bay Area...

Concerning...Heavy rainfall

Valid 031800Z - 040600Z

SUMMARY...AR continues though orientation will become more NE-SW
with time as weak height-falls and shortwave press slow moving
cold front southwest toward the Redwood Coast of California and
increasing rainfall potential with some embedded convective
elements possible with hourly rates of .33-.5".

DISCUSSION...18z surface analysis depicts an atypically well
defined surface front across NW NV into the northern portions of
the CA Sierra Nevada into the southern slopes of the Trinity
mountain and toward a weak surface wave near Cape Mendocino.=20
Strong southerly veering to southwesterly flow through the
northern Valley continues to intersect and ascend with moderate
moisture into the upper 40s/lower 50s in Tds. Cold air into SW OR
allows for a fairly steep isentropic ascent pattern to maintain
light to moderate rainfall across the rim of mountains across the
northern Valley with snow levels still above most but the highest
peaks of the terrain. As such, prolonged .15-.25"/hr rates are
likely to continue for a few more hours before the orientation of
the AR/plume changes with the advance of the front; generally with
a fulcrum/pivot point of the plume centered in N CA near
Shasta/Siskyou county line.

GOES-W IR and WV suite show a defined shortwave comma
east-southeast of the 40N130W benchmark continuing to advance
rapidly northeast under the influence of the rapidly exiting 150kt
jet streak and associated right entrance region. As the
ascent/shortwave-ridge pattern passes with this entrance region,
influence of surface to 850mb northwesterly flow will allow for
eastward progression of the well defined frontal zone. CIRA LPW
sfc-850mb layer shows the stark moisture difference across the
boundary with solid .5" over-topped by .25-.3" at 850-700mb and
further solid core of subtropical moisture already at 700-500mb along/downstream of the shearing shortwave to further increase
total moisture to over 1" nearing 1.25" intersecting the Redwood
Coast southeast of Cape Mendocino. The shortwave is expected to
further elongate/shear while reaching the NW CA coast by 00-02z
period and the associated cold front intersection with the coast
will drop southeastward. Forty-five to 60 degrees of sfc-850
25-35kt confluent flow will support IVT to increase slowly from
300-400 to 400-600 kg/m/s as the core of deepest moisture overlaps
after 00-06z. Some mid-level CAA may support very weak vertical
development given 50-150 J/kg possible; though driving mechanism
is likely to be more low level convergence and orographic ascent
across the Coastal Range. Typical .25-.33"/hr may occasionally
increase to .5"/hr across S Mendocino county into Sonoma county
after 00z. Scattered showers may extend into the Bay and Santa
Cruz mountains late in the period (03-06z), though rates are not
likely to be sizable for any flash flooding with exception of most
susceptible urban locations.

...Northern Valley/Lower Slopes of Sierra Nevada...
Southerly flow will veer to more southwesterly and increase
orographic ascent toward perpendicular as the shortwave/DPVA
crosses the region after 00z. Solid remaining moisture in the
valley will ascent and present solid potential for .25-.5"/hr
rates resulting in spotty totals of 2-2.5" by 06z. Given recent
heavy rainfall and increased upper soil saturation increased
run-off will occur resulting in areal expansion of increased
riverine stream flows.

All locales and rates are likely to be below critical values for
any flashy style flooding and so will keep the tag on this
discussion at Heavy Rainfall but will continue to monitor for any
highly localized issues that may unfold.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5NT9hdA1JDhaj4Y1NVc-AQ5Osz_eKHK8Hq3u18ZgRFhg6FFoR-LJP0Siff8Lgcpr-N_u= S4j1gv4W9wxECn3Yf4sNI44$ for graphic product...

ATTN...WFO...EKA...MFR...MTR...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41412218 41392159 41082138 40842145 40682170=20
40402166 40062151 39822115 39602081 39192055=20
38772036 38372059 38532160 38292196 37802207=20
37182183 36892198 36952237 37972305 38442344=20
38962384 39722393 40052434 40502446 40972405=20
40732365 40942346 40832288 41112243=20

=3D =3D =3D
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AWUS01 KWNH 040556
FFGMPD
NVZ000-CAZ000-041800-

Mesoscale Precipitation Discussion 0018
NWS Weather Prediction Center College Park MD
1256 AM EST Tue Feb 04 2025

Areas affected...Central and Northern California

Concerning...Heavy rainfall

Valid 040600Z - 041800Z

SUMMARY...Heavy rain associated with the ongoing atmospheric river
may locally reach rates to 1 inch per hour with any convective
banding and heavier showers through mid-morning.

DISCUSSION...The primary AR has shifted into the Bay Area and
northeast through Sacramento this evening. For most areas, the
rain is generally light to moderate, producing 1/10 to 1/4 inch
per hour rates. The higher 1/4 inch per hour rates are largely on
the windward (southwest-facing) sides of the coastal ranges and
the Sierras. Onshore flow to 40 kt at 850 continues into the Bay
area. Upon moving inland the flow shifts to southerly as it tracks
along the foothills of the Sierras up the Sacramento Valley. This
low level jet has been the primary driver of the moisture
advection producing locally heavier rains in the form of
convergent bands and enhanced upslope rainfall activity over the
past few days. Since the LLJ isn't going anywhere, these local
"flare-ups" of heavier rain will continue through the overnight
and into Tuesday morning.

The band is expected to shift south of the I-80 corridor by around
10Z/2am PST based on all of the latest HiRes guidance. This will
leave the I-80 corridor from San Francisco through Sacramento in
off-and-on shower activity. The band will taper a bit as it stalls
out generally from a Monterey to Modesto line through the rest of
the overnight and into Tuesday morning. For far northern
California, the area is in a much needed break right now in most
areas, though very light rain and higher elevation snow continues
north of Redding. This break in the rain will continue through at
least sunrise as noted by the relative lack of higher cloud cover
off the coast of California on the graphic.

The next low is following swiftly behind this latest round.
Guidance has shifted significantly northward in the latest runs.
Thus, now expect another round of heavy rain to impact much of the
Sacramento Valley, including the hard-hit Redding area. This
heavier rain will arrive with the next low around 15Z/7am PST. IVT
values with the low will increase to around 750 kg/ms according to
CW3E interpolations of the GFS along the coast. The low will be
supported by a quickly-advancing zonal jet stream moving in from
the Pacific, so northern California will be in the left exit
region of that jet. The surface low will thus be supported by
favorable upper level dynamics. The heavy rain will be further
supported by the strengthening LLJ in the Sacramento Valley, which
will intensify in response to the approaching low and increasing
pressure gradient. It's likely that any 1 inch per hour rates with
any convergent bands will occur from mid-morning on due to the
additional moisture and advection.

Any resultant flooding from the heavy rain will likely be confined
to urban areas and flood-prone streams and creeks.

Wegman

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!59G7LOfcoquUdQ5I44TLMUtD7kBqieQZlczqOHpWckco43BIlk7w5Dc1x577hsedxg-G= epVnUC0EIUZOlvbjghhm55A$ for graphic product...

ATTN...WFO...EKA...HNX...MFR...MTR...REV...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41642113 41392063 40972019 40202000 39102000=20
38591974 38091969 37492045 37112124 36902191=20
36992236 37492259 37812264 37972309 38182304=20
38992387 39512390 39902398 39952396 40322377=20
40672325 41062280 41582213=20

=3D =3D =3D
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AWUS01 KWNH 041813
FFGMPD
CAZ000-050600-

Mesoscale Precipitation Discussion 0019
NWS Weather Prediction Center College Park MD
111 PM EST Tue Feb 04 2025

Areas affected...Northern and Central California

Concerning...Heavy rainfall...Flash flooding possible

Valid 041800Z - 050600Z

Summary...Localized flash flooding is possible with additional
1-3"+ rainfall totals through 06z. Localities most likely to
realize isolated flash flooding from additional 3-5" totals are
along the northern foothills of the Sierras and the Santa Lucia
Range.

Discussion...Another round of moderate to heavy precipitation is
underway across portions of northern and central CA, driven by a
mid-level vort max leading an anomalous shortwave trough pivoting
into the Pacific Northwest (along with synoptic uplift provided by
upper-level divergence via the left exit region of a 130+ kt jet
streak). The 12z HREF indicates an additional 1-3"+ of QPF through
06z, with localities along the northern foothills of the Sierras
and the Santa Lucia Range most at risk of localized flash flooding
(with the highest chances for 0.5"+/hr rates and additional totals
of 3-5", per the 12z HREF 40-km neighborhood probabilities for
0.5" exceedance and ensemble agreement scale 0-100 km of 3.0"
exceedance, respectively). The HRRR has also been among some of
the wettest guidance, suggesting banded rainfall capable of
0.5-1.0"/hr rainfall rates extending into the lower elevations of
coastal regions (such as Santa Rosa and San Francisco). This seems
plausible, given the location of the surface boundary and the
uptick in low-level moisture flux convergence already underway per
SPC RAP analysis (along with the favorable synoptic environment
and total precipitable water values of 1.2"+ near the max moving
average, per OAK sounding climatology). Please consult local NWS
products for up-to-date information on flood hazards.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-3MqJeUTsCEduFm2c40d3KhB_DpG4USTTrHVrqWRBE724la5up9LZmQrMY6CbeVvHZIQ= fGwsoLslMkDywPsQgzK1dI4$ for graphic product...

ATTN...WFO...EKA...HNX...LOX...MFR...MTR...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41232226 41182197 40922182 40512171 40212157=20
39972125 39732092 39032065 38462016 37751965=20
37391947 36991909 36571882 36321867 36041878=20
36251903 36631941 36891963 37191985 37412019=20
37602049 37522078 37372103 37082126 36702152=20
36472146 36212119 35892084 35482062 35302078=20
35362137 35772195 36402232 37162279 37802305=20
38442338 38742315 39122321 39412339 39792365=20
40072361 40452342 40812310 40972275 41122236=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 060557
FFGMPD
MDZ000-VAZ000-WVZ000-OHZ000-KYZ000-061154-

Mesoscale Precipitation Discussion 0020
NWS Weather Prediction Center College Park MD
1256 AM EST Thu Feb 06 2025

Areas affected...much of West Virginia, far northeastern Kentucky

Concerning...Heavy rainfall...Flash flooding possible

Valid 060554Z - 061154Z

Summary...A gradual uptick in excessive runoff potential is
expected especially in central/eastern West Virginia through 12Z.
Local 1-2 inch rainfall totals are expected.

Discussion...Areas of light to moderate rainfall have developed
across much of the discussion area since 03Z, with several
observations of 0.5-1 inch rainfall totals noted. In addition to
the recent rainfall, an upstream scenario is favoring repeated
rainfall with heavier rates through 12Z, including: 1) upstream
shortwave energy encouraging updrafts across western KY/TN, 2)
increasing low-level flow impinging on a low-level boundary
near/along the KY/TN border, and 3) 40-60 knot low-level flow,
which was increasing instability/MUCAPE from west to east across
Kentucky and vicinity. The net result of this pattern is a
gradual increase in convective elements along a west-east axis
from western Kentucky through the discussion area. Nearly
continuous rainfall should occur through 12Z in most areas, with
spots of 0.25-0.5 inch/hr rain rates and 1-2 inch rainfall totals
expected.

These rainfall totals should fall across areas of wet soils from
antecedent rainfall over the past month from eastern KY into the
central Appalachians. FFG thresholds are generally in the 1
inch/3-hour range and are potentially lowering given ongoing
rainfall. The regime should support a few areas of
runoff/flooding especially across sensitive terrain in
central/eastern West Virginia.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8u5tbUgiwIZheyNTPlzDMifhCAMlBdj6Hb5O6QBIEXw_tPWEV3CBwUTr2jl5tQFtN51T= MZwco3xcbOTNj646mYFQZLk$ for graphic product...

ATTN...WFO...ILN...JKL...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 39377916 39007889 38137978 37548077 37458241=20
37928337 38258350 38538317 38878224 39208068=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 060822
FFGMPD
WVZ000-OHZ000-KYZ000-061321-

Mesoscale Precipitation Discussion 0021
NWS Weather Prediction Center College Park MD
322 AM EST Thu Feb 06 2025

Areas affected...northern/central Kentucky

Concerning...Heavy rainfall...Flash flooding possible

Valid 060821Z - 061321Z

Summary...At least minor/isolated flash flood potential should
continue through 13Z or so as upstream convection near the
Mississippi/Ohio River confluence migrates eastward through the
discussion area.

Discussion...Persistent, repeating convection along an axis from
near Lexington, KY to near Huntington, WV has produced several
areas of 1-1.75 inch rainfall totals over the past 3-6 hours
despite relatively quick movement. The rainfall associated with
these storms has wet soils considerably across the region, with
most recently updated FFG thresholds lowering into the 0.25-0.75
inch/hr range and MRMS Flash responses suggestive of at least
isolated, minor flooding and runoff issues existing along that
corridor.

Convection upstream of this region is causing some concern that
perhaps another uptick in flash flood potential might occur
between 09-13Z. This convection is expected to expand due to 1)
forcing for ascent aloft associated with mid-level vort maxima
across IL/IN, 2) fast low-level flow impinging on a warm front in
western KY, and 3) increasing MU/SBCAPE across the region. CAMs
generally follow suit with this thinking, suggesting another round
of potential training convection entering the Lexington/Huntington
axis between 10-13Z with possible 0.25-0.75 inch/hr rain rates.=20

Should this potential materialize as forecast, isolated flash
flood potential can be expected especially in the 10-13Z timeframe.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Dbq6sRFf-TmWAgKxEN9tpF57_2A46cfFrfpBZfR6GDUtFhpx-71Wt25V371NY16Y7ly= aHQuREIgM8AVbkSlD_tx01g$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...RLX...

ATTN...RFC...OHRFC...NWC...

LAT...LON 38728286 37988244 37468285 37208508 37498620=20
38138567 38578468=20

=3D =3D =3D
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AWUS01 KWNH 061300
FFGMPD
VAZ000-WVZ000-KYZ000-061830-

Mesoscale Precipitation Discussion 0022
NWS Weather Prediction Center College Park MD
800 AM EST Thu Feb 06 2025

Areas affected...South-central & Eastern KY...Southern WV... Far
Western VA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 061300Z - 061830Z

SUMMARY...While intensity and coverage is on a downward trend, a
few cells will remain capable of intense rain rates of
1.25-1.5"/hr over saturated soils for scattered incident or two of
flash flooding through the remainder of the morning.

DISCUSSION...GOES-E WV suite shows the core of the triggering
shortwave energy along the base of the broader synoptic trough has
slid across central Ohio with trailing tail crossing northern KY
along/ahead of the approaching 130+kt flat upper-level jet. This
orientation continues to provide solid broad scale ascent with
DPVA south and eastward across the area of concern, accompanied by
solid divergence to maintain ongoing convective activity across
the warm sector. Surface and VAD wind profiles also denote the
speed and directional confluence/convergence supporting the active
line of cells with about 30-45 degrees of convergence in both
10-20kts of sfc and 50 to 60kts of 850mb flow. Additionally, this
confluence zone continues to align with diminishing but
sufficient unstable air mass with mid-60s temps over upper 50s/low
60s Tds and modest lapse rates for 750-1000 J/kg of SBCAPE across
south-central to southeastern KY reducing across WV to below 500
J/kg.

As such, overall trends have been toward slightly warming tops;
however, there remain some stronger/broader updrafts with weak
rotation across southern KY to tap all the available low level
moisture (over 1.25" total PWats), to allow for some remaining
efficient rainfall with sub-hourly rates resulting in some totals
over 1-1.25" in quick duration. Instability and rates will
diminish through the morning, but west to east cell motion and
inflow from the southeast into increasing terrain should help for
some orographic enhancement as well to maintain a low-end
scattered threat for intense rates.=20

While orientation of the convergence/convective line has become
more oblique to the mean steering flow, reducing the capability
for much higher totals from training noted overall; the soil
conditions across E KY into S WV/W VA remain cold and highly
saturated with NASA SPoRT LIS 0-40cm soil ratios well over 75%
with some spots near 90% in higher terrain that may still have or
recently just lost the majority of snow pack. As such, FFG values
are very low (1-1.5"/hr) naturally and with little capacity for
uptake especially in remaining sub-hourly intense rates...even has
they diminish with reducing instability into late morning,
incidents of flash flooding will remain possible.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4QeDRkGcVP3I_A0OHqJcVfoqVaN09OCm6L59ruCauiCi-ZP8B0HE2_GPbwyy0ITJEJdY= XHekTKSHT7OVBkq_Z6OdEhs$ for graphic product...

ATTN...WFO...JKL...LMK...MRX...RLX...RNK...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38778098 38658043 38308041 37908075 37228132=20
36698199 36628406 36738564 37078586 37408487=20
38088309 38468188=20

=3D =3D =3D
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AWUS01 KWNH 061444
FFGMPD
CAZ000-070300-

Mesoscale Precipitation Discussion 0023
NWS Weather Prediction Center College Park MD
943 AM EST Thu Feb 06 2025

Areas affected...Coastal Ranges, Sacramento Valley and Lower
Slopes of Sierra Nevada in California

Concerning...Heavy rainfall...Flash flooding possible

Valid 061500Z - 070300Z

SUMMARY...Compact, quick moving storm with anomalous moisture flux
to affect mainly coastal ranges at first but by late afternoon
transition to more convective localized convective showers with
training potential. Given rates up to .5"/hr, locally 2-3" totals
are possible in favored orography.=20

DISCUSSION...GOES-W WV suite denotes a compact, increasingly
well-defined southern stream shortwave and associated surface low
near 38N and 128W lifting east-northeast with expanding baroclinic
shield downstream starting to cover much of northern California.
This wave/low will continue to strengthen and occlude further
throughout the day as northern upstream persistent upper-low
finally swings southeast and provides further DPVA and sharpens
the entrance region to the strengthen upper-level jet streak;
while steepening lapse rates with cold advection aloft (mainly
affecting northern CA later in the forecast period, after 00z),
prolonging the onshore flow and potential for locally heavy
rainfall.

RAP analysis/forecast shows strong warm advective pattern
approaching the central California coast with southerly 30kt 850mb
winds veering to 50-65kts in the 17-19z period. The nose of the
LLJ is also accompanied by the core of a narrow warm
conveyor/moisture axis with 1-1.25" total PWats (though CIRA LPW
suggests this is mainly below 700mb) and trends continue to direct
it centered from Monterey Bay southward along the Santa Lucia
Range. IVT values appear to be 600-700 kg/m/s and given
orthogonal ascent to the southern Santa Cruz and Santa Lucia
range, rates of .33-.5"/hr are likely to commence with the arrival
of the warm front around 17-18z and continue for 5-6hrs, with a
very slow southward drift of the core of the LLJ/moisture axis.=20
This magnitude of moisture flux is about 5 standard anomaly above
normal even in the wet season. As such, localized totals of 2-3"+
are probable along the range. Later in the afternoon, the plume of
moisture sags south and rounds Cape Conception around 00z, winds
will slowly be diminishing to about 30kts at 850mb; there is some
more oblique (45-60 degrees) of orographic ascent in the
mid-levels, but southerly surface flow will not increase until
after the forecast period as the cold front rounds the bend. So
at this time there is mixed signals to potential for sizable rates
over the fresh burn scars across the eastern Transverse Ranges, so
while not completely improbable for flash flooding/mudslides by
03z, we will be monitoring closely for potential for a targeted
MPD if conditions increase/warrant it later into this
evening/overnight.

Meanwhile, further north the western branch of the TROWAL will
provide ample moisture flux wrapping north of over the
surface-850mb low to feed surface upslope forcing to allow for
moderate rainfall with .25-.33" rates along the coastal ranges
north of the San Francisco Bay; which should slowly expand
eastward through into the lower slopes of the Trinity to northern
Sierra Nevada Ranges. As the upper-level northern stream DPVA
swings southeast, providing some cooling aloft and steepening
lapse rates, it will also help to sharpen the
deformation/convergence zone across NW CA as the surface low
transitions from coastal to northern central Valley from 23-01z.
An uptick in convective activity with slight reduction in forward
speed may result in spotty .33-.5"/hr rates across the
Redwood/Lost Coast resulting in localized totals of 2-3" by 03z as
well, this should remain more of a heavy rainfall risk as the
older burn scars are less susceptible, but an isolated
creek/stream with quick rise is not completely out of the picture
given soil conditions remain above average in the 80-95
percentiles even for this time of year given recent rainfall.=20

Bottom-line, this quick hitting/strong moisture flux is highly
anomalous even in the wet season but the overall rates and totals
still generally remain below flash flooding concerns and will hold
with a 'heavy rainfall' tag at this time; however will convective
trends closely for any potential targeted MPDs and flash flooding conditions.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_m8IGq-VPPGXEQyevjqhrrzrpAKV7GP0muBc3Y085SJcZwXQPsBVIx3odYIwSQaiWOVe= yRxGb-5-ycijb610wIr1vsI$ for graphic product...

ATTN...WFO...EKA...HNX...LOX...MTR...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 40862210 40712184 40432167 40082152 39602087=20
39172059 38832038 38522027 38141999 37601966=20
37271940 36881906 36511880 36191865 35951876=20
36131904 36361928 36671951 37201977 37752022=20
38092079 37922118 37852141 37492161 37032143=20
36472092 35972040 35722025 34981988 34761927=20
34551873 34071906 34331984 34422053 34812083=20
35452118 36102182 37532286 38292338 39092396=20
39782422 40382392 40422342 40172319 39972297=20
39912271 40212264 40582251 40842237=20

=3D =3D =3D
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AWUS01 KWNH 062159
FFGMPD
VAZ000-WVZ000-TNZ000-KYZ000-INZ000-070357-

Mesoscale Precipitation Discussion 0024
NWS Weather Prediction Center College Park MD
458 PM EST Thu Feb 06 2025

Areas affected...portions of KY and southwest VA

Concerning...Heavy rainfall...Flash flooding possible

Valid 062157Z - 070357Z

Summary...Showers and thunderstorms within a saturated atmospheric
column over saturated soils are expected to lead to hourly rain
totals to 1.5" and local amounts to 3". This could lead to flash
flooding over saturated soils and urban areas.

Discussion...Recent radar imagery shows quick-moving but scattered
showers and thunderstorms forming and moving through western KY at
the present time. They are elevated in nature and forming on the
back side of a frontal zone with a few surface waves on the south
side of a broad shortwave trough in the Great Lakes, utilizing
500-1000 J/kg of MU CAPE. Other activity to the southeast is much
closer to the surface front. At the moment, the flat wave in
western TN is closest to the back edge of the convection.=20
Precipitable water values of 0.75-1.25" lie across the region
within a cool air mass, leading to almost complete saturation.=20
Effective bulk shear is ~50 kts, which is enough for both linear
convective organization and mesocyclone formation.

Flash flood guidance values are fairly low, roughly 1" in three
hours -- within the past 24 hours, 1-3" of rain fell in this area.
With the expectation of 0.5"+ an hour totals, possibly as high as
1.5" in an hour, expected over the next several hours as the
storms propagate generally east-southeast parallel to thickness
lines, flash flood guidance exceedance could occur in scattered
spots where cells can train/two or more mesocyclones can align.=20
The progressive frontal boundary and quick cell movement should
keep rain amounts from getting exceptionally high. Hourly totals
to 1.5" with local amounts to 3" are the expectation, which could
lead to flash flooding in urban areas and over saturated soils and
hilly topography.

Roth

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4hjqNsAz6I_CgvsCe2AdIOO_gfHq22emXLJFkkxZcrzBwWbHk8xyOFB25QZTRoWSnQ43= PyYx9RdN4MljM43fwdPmtzI$ for graphic product...

ATTN...WFO...JKL...LMK...MRX...OHX...PAH...RLX...RNK...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38228453 37108114 36598259 36368416 36528789=20
38218643=20

=3D =3D =3D
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AWUS01 KWNH 070318
FFGMPD
NVZ000-CAZ000-070916-

Mesoscale Precipitation Discussion 0025
NWS Weather Prediction Center College Park MD
1017 PM EST Thu Feb 06 2025

Areas affected...much of California

Concerning...Heavy rainfall...Flash flooding possible

Valid 070316Z - 070916Z

Summary...Flood/flash flood potential should continue on at least
an isolated basis through 09Z/1a PST. An additional 1-2 inches of
rainfall is expected along windward locations of the Sierra, and
locally higher amounts cannot be ruled out.

Discussion...Flood/flash flood potential is expected to continue
through at least 09Z this evening. Persistent lift associated
with an upstream mid-level wave west of Oregon continues to
support scattered to widespread shower activity across the region.
Additionally, strong southerly low-level flow (40-50 knots at
850mb) continues to support local terrain enhancement to rain
rates across windward locations of the Sierra, where hourly rain
rates nearing 0.25 inch were noted per MRMS near/southeast of
Redding. These rates have contributed to isolated flash flooding
and mudslides. This regime is expected to persist for several
more hours, with additional rainfall accumulations of 1-2 inches
expected. Wet (and moistening) ground conditions and ongoing
rainfall is expected to continue to foster at least isolated
instances of excessive runoff/flood impacts.

Around/after 09Z, models suggest the low-level flow enhancing
rainfall rates this evening will begin to weaken slightly.=20
Moderate to heavy rainfall should still remain in the area,
although a gradual decrease in the overall coverage of the
heaviest rainfall should commence. A gradual lessening of the
flash flood risk is also expected during this timeframe.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7sio6R-zD-MkEH7oU-5ZcgLLWkA77ovXv8xNE8-FPjMaKLIzGgMa50aRkvVG02OrovOx= fRjlFcDlzwbRkCjqOCf6qRI$ for graphic product...

ATTN...WFO...EKA...HNX...MFR...MTR...REV...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41242187 40582099 39452012 38001937 37381921=20
37161927 37201984 38132077 38812152 38512191=20
37612172 36792147 36512163 37682257 40012355=20
40912315 41172265=20

=3D =3D =3D
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AWUS01 KWNH 070349
FFGMPD
CAZ000-070948-

Mesoscale Precipitation Discussion 0026
NWS Weather Prediction Center College Park MD
1048 PM EST Thu Feb 06 2025

Areas affected...portions of southern California

Concerning...Heavy rainfall...Flash flooding possible

Valid 070348Z - 070948Z

Summary...Increasing onshore flow is interacting with the
Transverse Ranges in southern California to produce scattered
showers and locally heavy rainfall. Rainfall totals of 0.25-1
inch are possible through 10Z/2am and beyond. Excessive runoff
and debris flows are a distinct possibility - especially near
sensitive areas of variable terrain and near burn scars.=20

Discussion...Over the next several hours, a strong low-level
cyclone (currently centered near Eureka) will migrate
northeastward toward Oregon. As this occurs, strong southwesterly
low-level flow will increase across portions of southern
California especially near terrain-favored coastal ranges. Moist
air (characterized by 1-1.1 inch PW values) will accompany the
increasing flow and become forced over the Transverse Ranges,
resulting in areas of orographically enhanced moderate to heavy
rainfall. This process is already underway, with spots of 0.2-0.4
inch/hr rain rates already observed west of Los Angeles in the
past hour very near Malibu and Castaic. These trends are expected
to continue, and a roughly 6-12 hour window of heavier rainfall
potential will exist across the discussion area continuing into
the overnight hours (perhaps through 12Z-15Z Friday).

These areas of heavy rainfall will occur in areas of sensitivity
from both terrain and burn scars from recent fires across the
region. As a result, areas of flooding and debris flows are
possible. Rainfall totals of 0.25-1 inch are probable through
10Z, with locally higher amounts (exceeding 1.5 inches) possible
in terrain-favored areas.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8xHNefkHYP3_lJgJJICRRL1GK8_LbVx7lSPiJ3pel_wzghsP-I4EeifkSzULBluoOydH= JBQwRntAtlaAIl5l-aQqq0E$ for graphic product...

ATTN...WFO...HNX...LOX...SGX...VEF...

ATTN...RFC...CNRFC...NWC...

LAT...LON 35242052 35241936 35121841 34921756 34291731=20
33971765 34001857 34512041 34842065=20

=3D =3D =3D
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AWUS01 KWNH 080741
FFGMPD
VAZ000-WVZ000-OHZ000-KYZ000-081340-

Mesoscale Precipitation Discussion 0027
NWS Weather Prediction Center College Park MD
240 AM EST Sat Feb 08 2025

Areas affected...much of West Virginia and a small part of eastern
Kentucky

Concerning...Heavy rainfall...Flash flooding possible

Valid 080740Z - 081340Z

Summary...At least minor/isolated runoff issues could develop in
the next few hours as moderate rain moves in from central/northern
Kentucky through 14Z.

Discussion...Strong convergence on the nose of a 40-kt low-level
jet over western Kentucky has aided in development of moderate
rainfall generally along an axis from near Louisville to near the
WV/KY border near Pikeville. Within this axis, the persistence of
rainfall has allowed for MRMS-estimated areas of 0.10-0.30 inch/hr
rain rates to materialize. The axis was also parallel to robust
westerly flow aloft (supporting persistence), and recent radar
mosaic imagery indicates upstream shower activity near the MS/OH
River confluence poised to move through areas currently affected
by moderate rainfall. The net result of this pattern is a fairly
prolonged period of light to moderate rainfall eventually
extending into West Virginia, with 0.75-1.25 inch rainfall totals
expected through 14Z across the discussion area.

Despite modest rain rates, soils are wet across the area from
recent rainfall and FFG thresholds are 1) ~0.25 inch/hr and 2)
less than 1 inch/3-hr across parts of the region (especially in
hillier terrain in eastern WV). These thresholds and recent flash
flood events suggest that ground conditions are extremely
sensitive. The moderate rainfall moving in from Kentucky should
persist for several hours, resulting in at least isolated
instances of excessive runoff/flooding. The uptick in flood risk
should persist in the 0830Z-1400Z timeframe and beyond as
low-level convergence strengthens across the area through the day.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_gr4qwKw5K5jYf9hzwSVfd5OU0gHU4AZ65N0702g3mo6SY0OyiHomCv70lD39JquYytq= XuS7c2SyHio4hQsMcSo5XK8$ for graphic product...

ATTN...WFO...ILN...JKL...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 39108015 39037954 38687946 38157973 37708021=20
37518090 37498204 37568309 38528343 38888208=20
38988118=20

=3D =3D =3D
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AWUS01 KWNH 090206
FFGMPD
VAZ000-WVZ000-OHZ000-KYZ000-090804-

Mesoscale Precipitation Discussion 0028
NWS Weather Prediction Center College Park MD
906 PM EST Sat Feb 08 2025

Areas affected...southern West Virginia, far eastern Kentucky

Concerning...Heavy rainfall...Flash flooding possible

Valid 090204Z - 090804Z

Summary...Fast-moving showers could produce a quick 0.25 inch of
rainfall across the discussion area through 05-06Z. Extremely
sensitive ground conditions suggest potential for
efficient/excessive runoff and impacts during this timeframe.

Discussion...Forcing/ascent along and ahead of a cold front has
aided in development of a couple bands of convection extending
from Parkersburg to Huntington to Somerset, KY. These showers
were in a marginal environment in terms of instability, although
~100 J/kg MUCAPE appears to support updrafts along and ahead of
the front. Quick movement (from 70 kt mean steering flow) has
limited rain rates so far, although recent MRMS data suggests
pockets of 0.1-0.2 inch/hr rates near Jackson, KY over the past
hour.

These showers will move toward portions of the discussion area
that are extremely sensitive to any additional rainfall. NASA
SPORT soil moisture values are near 100% across the area amid
plenty of antecedent rainfall (including 1-1.5 inch totals in the
past 24 hours). FFG thresholds generally range from 0.25-0.5
inch/hr, but are near zero in a few spots. Several impacts were
also reported this from this morning's round of rainfall.=20
Incoming rainfall along/ahead of the front may result in an uptick
in excessive runoff and flood potential through 07Z.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6CEl1e3dRVBZoJxLJsa61bKoSMJFD78rTxWcNS0IlUX6QYExwTPlGoyKjjoYiqi6dcik= Vqkxvao6vBmbl3PUftyaBpo$ for graphic product...

ATTN...WFO...JKL...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 39258120 39198015 38957938 38497951 37768007=20
37438073 37308138 37478217 38198265 38988194=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 120928
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-121526-

Mesoscale Precipitation Discussion 0029
NWS Weather Prediction Center College Park MD
427 AM EST Wed Feb 12 2025

Areas affected...much of Louisiana, central/southern Mississippi,
and a small part of east Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 120926Z - 121526Z

Summary...Convective bands will continue to increase and grow
upscale into clusters and lines while moving eastward across the
discussion area. A few areas of 1-2 inch/hr rain rates are
expected, which should pose a flash flood risk especially near
sensitive areas.

Discussion...Over the past hour or so, radar mosaic imagery has
depicted a distinct uptick in convective activity across east
Texas and Louisiana. The increase in convection is likely tied to
a dramatic increase in southerly 850mb flow along the Sabine River
Valley (into the 40-60 kt range) along with attendant
convergence/ascent. The eastward movement of a distinct mid-level
shortwave trough and steep lapse rates aloft were also
contributing factors to the increase in convection. Most storms
are elevated above a cool stable boundary layer, although mergers
and growth into linear segments with localized training have
already been observed near/just east of Lufkin, where spots of 1
inch/hr rain rates were already estimated via MRMS.

These convective trends are expected to continue, with
observations and CAMs both suggestive of upscale growth into one
or two dominant complexes that move eastward across the region.=20
Many cell mergers are anticipated and localized training will
remain a distinct possibility. These factors should contribute to
occasional 1-2 inch/hr rain rates at times as storms move eastward
through the discussion area. These rates should approach FFG
thresholds - especially along an axis from Lufkin to Greenville to
Columbus where prior rainfall has contributed to wet soils and
<1.5 inch/hr FFG thresholds. Prolonged rainfall along and south
of this axis (i.e., greater than 1 hour of heavy rainfall) may
also result in flash flooding. This threat is expected to persist
through 15Z, with occasional convective redevelopment in east
Texas indicated in the models throughout the morning.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7lIa7zzacsrpPgW07lPFC80pQTiBIi1dUIuuMNf9dXQ_UvaMihtl4fGGQ3H3scWSq11f= CVF68sukC-fDK3-OoZLRXG4$ for graphic product...

ATTN...WFO...HGX...JAN...LCH...LIX...MEG...SHV...

ATTN...RFC...LMRFC...SERFC...WGRFC...NWC...

LAT...LON 33888837 33218839 32128857 31239008 30539215=20
30489469 31609498 32489388 33409101 33838960=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 121519
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-122031-

Mesoscale Precipitation Discussion 0030
NWS Weather Prediction Center College Park MD
1018 AM EST Wed Feb 12 2025

Areas affected...Lower Missisippi Valley

Concerning...Heavy rainfall...Flash flooding possible

Valid 121518Z - 122031Z

Summary...Showers and thunderstorms will expand in coverage and
begin to train from SW to NE through the afternoon. Rainfall rates
in excess of 1"/hr will become more common, which through training
may produce 2-3" of rain. This could lead to instances of flash
flooding.

Discussion...The regional radar mosaic this morning depicts two
areas of heavy precipitation spreading across portions of the Gulf
Coast and lower Mississippi Valley states. A meandering stationary
front analyzed by WPC draped from northern MS into eastern TX is
providing focus for a corridor of convection, while a more broad
warm front slowly lifting across LA/MS is helping to spawn warm
advection showers and isolated thunderstorms. In general, rainfall
rates this morning have been between 0.25 and 0.5 inches per hour,
but a few embedded 1"/hr cells have recently been observed via
MRMS radar estimates. This has produced locally 2-3" of rain in
the past 6 hours, and a few flood advisories are currently in
effect.

As the morning progresses into the afternoon, upstream troughing
across the Central Plains will amplify, with synoptic ascent
becoming enhanced across the region through height falls, PVA, and
an intensifying jet streak aloft. Together, this will help lift
the warm front more steadily northward, leading to greater
instability drawing northward and impinging into the stationary
front. This is reflected by impressive moisture transport vector
convergence later this morning, especially from northern LA into
northern MS. As CAPE climbs to 500-1000 J/kg, this will support
more widespread convective rain rates which the HREF indicates
have a 20-40% chance of exceeding 1"/hr, with short term rain
rates potentially eclipsing 2"/hr as shown by the HRRR 15-min
fields. Storm motions will remain quick on 850-300mb winds of
40-60 kts, but organization along this boundary and some
backbuilding into TX will support training. This suggests that
despite the fast motion of individual cells, some areas may pick
up 2-3" of rain.

The soils across this region are generally saturated as noted via
NASA SPoRT 40cm soil moisture that is around the 90th-95th
percentile. This has reduced FFG to just 1-2"/3 hrs, or less, in
many areas, for which the HREF suggests has a 20-50% chance of
exceedance in the next few hours. This is further reflective of
the isolated potential for flash flooding into this afternoon.


Weiss

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5eDLGJEwOksezvhbZNpBWprRz3gZUBB61rszsHvK2Q2fLtc_mwlEocph5LRwhyUAkwSs= tbV3sRDDzZmp40aMZ8EYLHo$ for graphic product...

ATTN...WFO...JAN...LCH...LZK...MEG...SHV...

ATTN...RFC...LMRFC...SERFC...WGRFC...NWC...

LAT...LON 34238926 33958850 33368831 33048848 32578930=20
32039023 31339199 31039338 31069381 31169418=20
31549474 32279439 32789356 33479207 33969096=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 122026
FFGMPD
ALZ000-MSZ000-LAZ000-130215-

Mesoscale Precipitation Discussion 0031
NWS Weather Prediction Center College Park MD
326 PM EST Wed Feb 12 2025

Areas affected...Lower Mississippi Valley through Northern Alabama

Concerning...Heavy rainfall...Flash flooding possible

Valid 122024Z - 130215Z

Summary...Showers and thunderstorms rapidly blossoming within a
warm sector will expand in coverage and intensify through the
afternoon. These thunderstorms will lift northward and then train
SW to NE ahead of a cold front, with rainfall rates as much as
2-3"/hr. This could lead to instances of flash flooding.

Discussion...The regional radar mosaic across the Gulf Coast this
afternoon depicts rapidly expanding and intensifying thunderstorms
along and just south of a warm front from LA to the FL Panhandle.
This convection is expanding within a pronounced warm sector
characterized by favorable instability (MLCAPE 1000-2000 J/kg) and
elevated PWs (1.6 to 1.8 inches) according to the SPC
mesoanalysis. Additionally, recent VWPs from the region indicate
modest low-level veering but with strong inflow, supporting large
updrafts capable of producing intense rainfall rates. This is
being analyzed by recent MRMS 15-min rainfall as high as 0.75"
(3"/hr rates), resulting in rising CREST unit streamflow values
across parts of LA and MS. Upstream of this fresh convection, a
wave of low pressure and attendant cold front are analyzed by WPC
crossing from TX into LA, along which additional thunderstorms are
occurring with current FFWs.

As the afternoon progresses into the evening, the environment
should become increasingly unstable as the plume of 1000-2000 J/kg
MLCAPE surges as far north as Birmingham, concurrent with elevated
PWs being drawn northward. This plume of robust thermodynamics
will be advected on 850mb inflow that is progged to reach 50+ kts,
resulting in 850-700mb moisture flux that may exceed 5 sigma
according to the SREF. Additionally, increasing synoptic lift
within the RRQ of an intensifying jet streak will support an
expansion of convection into the evening, with thunderstorms
likely aligning along or just ahead of the convergence axis of the
approaching cold front as it squeezes the warm sector. This
alignment will rapidly enhance the flash flood risk, as training
of cells along the boundary will offset the limiting storm speed
of 40-60kts.

The HREF suggests that coverage of rainfall rates exceeding 1"/hr
will expand, and the HRRR 15-min progs suggest rainfall intensity
may produce 0.75 to 1 inch of rain in as little as 15 minutes.
These rates themselves could cause instances of flash flooding,
but where training occurs, more than 3" of rain is possible,
enhancing the flash flood risk. The most likely locations for any
flash flooding will be across urban areas as soil moisture in
southern LA, MS, AL is drier than normal according to NASA SPoRT.
However, training of these intense rain rates could quickly
overwhelm even the drier soils, so flash flood instances are
possible anywhere across the discussion area into this evening.


Weiss

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7HS20P0xpH_2YeArlrAwCpCkIcjONWRgMCzQPbWsAxBFJQAM3nSAqEdYjgbLbHzZEWoP= UGLjng9UesXPUWDHdCY15PE$ for graphic product...

ATTN...WFO...BMX...HUN...JAN...LCH...LIX...MEG...MOB...SHV...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34828712 34538627 33658599 32878613 32308688=20
31708793 31268939 30989077 30979206 30969237=20
31009261 31569255 32349167 34568837=20

=3D =3D =3D
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AWUS01 KWNH 122031
FFGMPD
ALZ000-MSZ000-LAZ000-130215-

Mesoscale Precipitation Discussion 0031...Corrected
NWS Weather Prediction Center College Park MD
331 PM EST Wed Feb 12 2025

Corrected for updated graphic

Areas affected...Lower Mississippi Valley through Northern Alabama

Concerning...Heavy rainfall...Flash flooding possible

Valid 122024Z - 130215Z

Summary...Showers and thunderstorms rapidly blossoming within a
warm sector will expand in coverage and intensify through the
afternoon. These thunderstorms will lift northward and then train
SW to NE ahead of a cold front, with rainfall rates as much as
2-3"/hr. This could lead to instances of flash flooding.

Discussion...The regional radar mosaic across the Gulf Coast this
afternoon depicts rapidly expanding and intensifying thunderstorms
along and just south of a warm front from LA to the FL Panhandle.
This convection is expanding within a pronounced warm sector
characterized by favorable instability (MLCAPE 1000-2000 J/kg) and
elevated PWs (1.6 to 1.8 inches) according to the SPC
mesoanalysis. Additionally, recent VWPs from the region indicate
modest low-level veering but with strong inflow, supporting large
updrafts capable of producing intense rainfall rates. This is
being analyzed by recent MRMS 15-min rainfall as high as 0.75"
(3"/hr rates), resulting in rising CREST unit streamflow values
across parts of LA and MS. Upstream of this fresh convection, a
wave of low pressure and attendant cold front are analyzed by WPC
crossing from TX into LA, along which additional thunderstorms are
occurring with current FFWs.

As the afternoon progresses into the evening, the environment
should become increasingly unstable as the plume of 1000-2000 J/kg
MLCAPE surges as far north as Birmingham, concurrent with elevated
PWs being drawn northward. This plume of robust thermodynamics
will be advected on 850mb inflow that is progged to reach 50+ kts,
resulting in 850-700mb moisture flux that may exceed 5 sigma
according to the SREF. Additionally, increasing synoptic lift
within the RRQ of an intensifying jet streak will support an
expansion of convection into the evening, with thunderstorms
likely aligning along or just ahead of the convergence axis of the
approaching cold front as it squeezes the warm sector. This
alignment will rapidly enhance the flash flood risk, as training
of cells along the boundary will offset the limiting storm speed
of 40-60kts.

The HREF suggests that coverage of rainfall rates exceeding 1"/hr
will expand, and the HRRR 15-min progs suggest rainfall intensity
may produce 0.75 to 1 inch of rain in as little as 15 minutes.
These rates themselves could cause instances of flash flooding,
but where training occurs, more than 3" of rain is possible,
enhancing the flash flood risk. The most likely locations for any
flash flooding will be across urban areas as soil moisture in
southern LA, MS, AL is drier than normal according to NASA SPoRT.
However, training of these intense rain rates could quickly
overwhelm even the drier soils, so flash flood instances are
possible anywhere across the discussion area into this evening.


Weiss

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5MQOgaXrGVUoKPJkQubelxBuZyrEYS24uHQXIN3l7yhjsj_2rwva_5FCBl-uLT7SYJgF= n5-HZtHsTQA859vPlm0_hRI$ for graphic product...

ATTN...WFO...BMX...HUN...JAN...LCH...LIX...MEG...MOB...SHV...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34828712 34538627 33658599 32878613 32308688=20
31708793 31268939 30989077 30979206 30969237=20
31009261 31569255 32349167 34568837=20

=3D =3D =3D
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AWUS01 KWNH 130221
FFGMPD
NCZ000-GAZ000-TNZ000-ALZ000-MSZ000-LAZ000-130820-

Mesoscale Precipitation Discussion 0032
NWS Weather Prediction Center College Park MD
920 PM EST Wed Feb 12 2025

Areas affected...Portions of Eastern LA...Southern MS...Much of
AL...Southeast TN...Northern GA

Concerning...Heavy rainfall...Flash flooding likely

Valid 130220Z - 130820Z

SUMMARY...Heavy showers and thunderstorms will continue to impact
the South overnight with concerns for high rainfall rates and
cell-training. Additional areas of flash flooding are likely which
will include the more sensitive urban corridors.

DISCUSSION...The latest radar and satellite imagery continues to
show a well-organized convective outbreak evolving across the
South with multiple bands of strong to severe convection,
including supercells, that are focusing corridors of locally
enhanced rainfall. A strong southwest low-level jet of 40 to 50+
kts continues to advance up across eastern LA through southern MS,
with it nosing up into areas of western and central AL. This is
fostering strong moisture transport along with the arrival of a
moderately buoyant airmass characterized by MUCAPE values of 1000
to 2000 J/kg.

Strong low to mid-level veering flow with height continues to
yield enhanced shear profiles favorable for supercells and these
more organized storms out ahead of an approaching cold front and
in vicinity of a warm front lifting northeast across the Southeast
have been tending to locally train over the same location this
evening.

Over the next few hours, areas of southern MS through central AL
in particular will continue to see cell-training and cell-merger
concerns as the convection attempts to evolve a bit more into a
QLCS which will still include embedded supercell concerns. By late
this evening and going well past midnight, areas of northwest GA
will begin to see more of the concentration of heavier convective
rainfall.

The evening CAM guidance, including the HRRR and the experimental
WoFS supports an additional 2 to 4 inches of rain with isolated
heavier amounts possible where the corridors of more organized
cell-training occurs, and this will be aided by rainfall rates of
generally 1 to 2+ inches/hour.

Some areas of flash flooding are already occurring, and the
additional rains over the next several hours should yield
additional areas of flash flooding. This will include especially
the more sensitive urban areas, which by later in the night may
include the Atlanta metropolitan area.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_3fNJtQJjYRscRkNcMOzrGhXFAUr56rJ10qzqoCtWZNkR97j4WNaN_fsQhuz9NB-qHqL= UURXVMq2s7XddsY3-NVIKYs$ for graphic product...

ATTN...WFO...BMX...FFC...GSP...HUN...JAN...LIX...MOB...MRX...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 35448488 35208370 34498325 33368365 31778605=20
30328893 29919032 30629034 32228877 33658741=20
34978636=20

=3D =3D =3D
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AWUS01 KWNH 130544
FFGMPD
CAZ000-131740-

Mesoscale Precipitation Discussion 0033
NWS Weather Prediction Center College Park MD
1244 AM EST Thu Feb 13 2025

Areas affected...portions of northern, central and southern CA

Concerning...Heavy rainfall...Flash flooding possible

Valid 130543Z - 131740Z

SUMMARY...Areas of heavy rain will overspread a sizable portion of
northern to south-central CA through 18Z Thursday ahead of an
approaching occluded cyclone. Some locations may see hourly
rainfall in excess of 0.5 inches for several hours with the
greatest potential for high rates along the Santa Lucia Range. 12
hour rainfall totals of 3 to 5+ inches are likely within areas of
favored terrain and heavy rain may produce areas of flooding/flash
flooding within urban areas and/or sensitive burn scars.

DISCUSSION...Loops of GOES West water vapor imagery through 05Z
showed a strengthening closed mid to upper-level low centered near
42N 134W. A strong, zonally oriented 250 mb jet axis was located
across 36N 140W, south of the closed low, with winds in excess of
150 kt located as far east as 134W per GOES West DMW vectors. The
location of the upper level jet max west of the upper trough axis
indicated the longwave trough was digging southward, but the
parent closed low appeared to be generally moving toward the east.
A ribbon of moisture streamed from west to east across the eastern
Pacific Ocean along a cold front connected into an occluded
cyclone over the eastern Pacific. TPW and LPW imagery showed that
the plume of moisture extended thousands of miles back to the
west, originating in the tropical west-central Pacific. However,
anomalous moisture was already located just off of the CA coast
with 00Z soundings from OAK and VBG showing PWAT values between
the 90th percentile and climatological max for mid-February. Warm
advection rainfall was already occurring in advance of the warm
front analyzed southeastward toward the south-central CA coast,
roughly 60 miles west of the coast of Monterey County.

As the closed low continues to advance off toward the east over
the next 6-12 hours, the attendant cold front is forecast to
steadily advance east and southeast, reaching the northern coast
of CA around 12Z. IVT values will steadily increase across the
central CA coast through 12Z peaking between 800-900 kg/m/s in the
vicinity of San Francisco. IVT values will remain above 600 kg/m/s
for a good portion of the central to south-central CA coast for
several hours with 850 mb winds peaking between 50-60 kt. The
orientation of the 850 mb flow is expected to be perpendicular to
the coast from North Bay to Point Conception.

Hourly rainfall in excess of 0.5 inches will become likely in and
around the higher terrain of San Francisco Bay by 09Z, perhaps
lasting for 3-5 hours. Farther south, hourly rainfall may reach 1
in/hr along the Santa Lucia Range given the favorable orthogonal
orientation of the low level flow to the axis of the mountain
chain. Downstream into the Sierra Nevada, snow levels are expected
to be near 7000 ft which will result in rainfall impacts to
potentially extend up to a relatively high elevation. Hourly
rainfall in excess of 0.5 inches may exceed 6 hours in duration
for portions of the central Sierra Nevada and Santa Lucia Range.
Sub-hourly rainfall rates over 0.25 inches in 15 minutes will be
possible within area of orographic ascent and boosted by weak
instability, though CAPE values are forecast to remain focused
below ~4 km AGL and stay below 250 J/kg by a majority of the most
recent guidance prior to 18Z.

12 hour rainfall totals through 17/18Z are expected to peak in the
3 to 5 inch range for the Coastal Ranges into the upslope regions
of the central Sierra Nevada, through higher totals may occur
within the Santa Lucia Range given a favorable low level wind
orientation. While flooding/flash flooding will be possible, it is
expected to remain on the low end of the scale and may be focused
across urban areas or perhaps lingering sensitivity on any area
burn scars.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5Xmh9Oowt5YmUjifd4UFwIY0mxZaT2flnAljU8G1GJgFwfOn4sGM2mM1sT_wTJ33SY2v= mCQsmDq9al77Us9izFuTJMQ$ for graphic product...

ATTN...WFO...EKA...HNX...LOX...MTR...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 40782243 40652194 40112164 39712119 39512070=20
39232058 38912037 38572025 38051987 37581950=20
37421919 37171914 37021903 36751880 36571874=20
36271862 35941838 35501850 35381881 36001952=20
36032012 35642002 35171970 34622061 35212158=20
35932251 37862346 39302456 39972518 40592460=20
40532360 40662277=20

=3D =3D =3D
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AWUS01 KWNH 130817
FFGMPD
FLZ000-GAZ000-ALZ000-131345-

Mesoscale Precipitation Discussion 0034
NWS Weather Prediction Center College Park MD
317 AM EST Thu Feb 13 2025

Areas affected...FL Panhandle into southeastern AL and central GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 130815Z - 131345Z

SUMMARY...A low probability threat for flash flooding due to
training will exist from the FL Panhandle into southeastern AL and
central GA through ~13Z. The threat will carry the potential for
rainfall rates in the 1-2 in/hr range within any areas of training.

DISCUSSION...Radar imagery at 08Z showed that a SW to NE oriented
axis of thunderstorms extended from the western FL Panhandle into
north-central GA. These thunderstorms were located out ahead of a
cold front and trends over the past few hours have shown a
weakening of the portion of the line over southwestern AL in favor
of strengthening of a new line out ahead, which was currently
crossing the western FL Panhandle. Recent infrared satellite/radar
trends through 08Z showed yet another line beginning to organize
about ahead of the existing convective axis, ~85 miles south of
Mobile Bay.

The environment within the warm sector was characterized by 500 to
1500 J/kg MLCAPE from the warm frontal position along the AL/GA
border to just south of the Gulf Coast along the FL Panhandle.
Flash flood guidance was lowest to the north (2-3 inches in 3
hours) and highest in western FL (4+ inches in 3 hours). The
greatest potential for high rainfall rates, near or even in excess
of 2 in/hr, will exist within the better instability across
southern locations.

Water vapor imagery showed a longwave trough over the central U.S.
advancing east, but with the base of the trough lifting north,
from OK to the MS Valley. This deamplification along the southern
end of the upper trough favors a gradual weakening trend of 850 mb
wind magnitude and of convective intensity over the AL/GA/FL
tri-state region. However, lingering instability and sufficient
low level moisture transport could allow for training if the
convective axis to the south continues to expand north and meets
with the ongoing northern portion advancing to the east at a
somewhat faster pace. While the general movement should be a
progressive eastward movement at 25-30 kt, There is a low end
chance that alignment of the heavy rain axis/axes will allow for a
brief period of training, which could contain rainfall rates of
1-2 in/hr, and local 2-3 inches of rain over a 2 to 3 hour window.
Localized flash flooding could result, but again, this threat
appears to be fairly low and recent CAM guidance does not support
much in the way of a flash flood threat over the next 3-5 hours.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7s8IP4xI0b1AYsqAUAimeiOmfPECkOXtCWqYtuKrqVX6k26DOppC74qbJEl_8Iojm-yn= PIyiCfeNtY13adK3mY0lnso$ for graphic product...

ATTN...WFO...BMX...CAE...CHS...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 33618302 33498228 33078167 32528146 31768171=20
30898320 30198408 29568500 30128734 31088690=20
32538513 33028448 33508380=20

=3D =3D =3D
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AWUS01 KWNH 131726
FFGMPD
CAZ000-140300-

Mesoscale Precipitation Discussion 0035
NWS Weather Prediction Center College Park MD
1225 PM EST Thu Feb 13 2025

Areas affected...Coastal Central and Southern
California...Foothills of Sierra Nevada...

Concerning...Heavy rainfall...Flash flooding likely

Valid 131730Z - 140300Z

SUMMARY...Strong Cyclone and atypically broad Atmospheric River
will have potential for .75"/hr rates and localized totals of 3-5"
in favored orographic ascent. Flash flooding is likely, especially
in lower FFG of Southern California. Significant flash flooding
may be possible in/near fresh burn scars.=20

DISCUSSION...GOES-W WV suite depicts a broad, fairly symmetric
closed low just off the NW coast of California continuing to bowl
ESE likely crossing the coastline much later tonight. This low is
atypically deep with the 90th to 95th percentile, but in
combination with fairly cold/stronger ridging downstream has
resulted in an atypically broad subtropical moisture plume with
1.25-1.5" total PWat values along upstream along/ahead of the
height-falls and associated cold front. GOES-W Vis/IR suite
denotes a stark cloud line with slightly anafrontal to the
southeastward cold front and moisture surge. Within the thick
stratus plume, 850-700mb flow is in the 50-65kt range and is
currently orthogonal to the Santa Lucia and Diablo Ranges,
presenting strong IVT/orographic convergence along the range.

...Central California/Sierra Nevada Foothills...
The IVT values are 4-5 standard anomaly units above seasonal
average and range about 700-900 kg/m/s. Rates have been slowly
increasing, with 3hr totals reaching 1-1.25" but will likely
increase with an additional .5-.75"/hr for maybe 1-2 hours as the
plume shifts southeastward. Totals already have reached 3-4" in
the Santa Cruz and northern Santa Lucia resulting in rapid stream
rises and some localized reports of flash flooding. The
additional 2-3" over the next few hours will likely result in
spots of 4-6" totals and continue the flash flooding risk.=20=20

Additionally, the plume has saturated the sub-cloud environment in
the San Joaquin Valley to allow for rain to reach the ground as
the core of the plume presses onshore. The warm front will press
through to the foothills and help to increased the depth of
orographic ascent resulting in spots of .75-1"/hr rates before
becoming very heavy snow at or above 7000Kft. This will decrease
with the passage of the plume/cold front and the flux will reduce
accordingly resulting in scattered shallow convective cells and
bands may aggravate the area given those steepening lapse rates,
which may have intense but brief cores of heavy rainfall/small
hail/graupel.

...Southern California...
Unlike further north, there is precedent moist airmass in place
across the California Bight/Channel Islands, surface to 700mb
values are above normal and total PWats are in the 1-1.25" range.
Currently, the warm front has progressed through the highest
terrain of the Transverse Range and winds are veering slightly
while increasing. This will allow for short-term increase in
orographic ascent across the Transverse (particularly east) and
Peninsular Ranges prior the main core of the AR/cold front later
this evening. Rates of .25-.33"/hr will increase as winds slowly
uptick from 15-20 to 30kts by 00z below 7500 Kft across the
ranges. Spots of 1-1.5" are probable to pre-soak the windward
facing topography.=20=20

A few hours prior to 00z, the cold front and AR will round Cape
Conception and winds will have solid veered profile with depth
with 40-50kts of 850-700mb flow fairly orthogonal to the range. A
few hi-Res CAMs suggest 100-250 J/kg may be present from slightly
higher theta-E air in place allowing for a subtle but important
uptick in vertical development that should result in .75"/hr rates
with spotty potential of 1"/hr. The growing concern here, is
while the plume is less orthogonal to the terrain the breadth of
the AR will allow for increased duration of exposure to the higher
flux. As such, below freezing levels, spots of 3-4" are probable
across the western Transverse Range by 03z and likely to be
similar toward the eastern and Peninsular Ranges thereafter. It
is not out of the realm of possibility that spots of 5" are
possible and heavy rainfall will extend to the coast with .5"/hr
rates and totals over 1-1.5" resulting likely flash flooding
conditions through the evening even for urban locations.=20=20

This is of particular concern given recent burn scars are going to
be less tolerable to any rates over .50"/hr let alone any
potential crossings of .75-1"/hr. It is too early to be certain
about any particular canyon/scar, but given hourly rates and
overall totals there is a sizable possibility for significant
flash flooding/debris flows in or near these scars and avoidance
of this prone areas is strongly advised. Please keep close
attention to local statements/warnings from WFO Los Angeles, state
and local emergency managers. It is possible a subsequent
targeted MPD may be required to address ongoing rainfall trends.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5Jo-Vnr9C7RceznyxJQj2mzaqf1eMMqjQu8gci3RUa33MtzZyNzLc3-bkHz0P8kSr9kP= RHKQXeh5NFj5hCkzyP5N6vM$ for graphic product...

ATTN...WFO...HNX...LOX...MTR...SGX...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 39472072 39042072 38382025 37511965 37171934=20
36811897 36291868 35631855 35491870 35611899=20
36381942 37042017 37252083 36982108 36442068=20
35832027 35381997 35141959 34871927 34721872=20
34681829 34651797 34351744 34271688 33721646=20
33041646 32571633 32541676 32521721 32761767=20
32821887 33141955 33592012 34292057 35002087=20
35632142 35912176 37062251 37762270 38112257=20
38602206 39002160 39242125=20

=3D =3D =3D
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AWUS01 KWNH 140217
FFGMPD
CAZ000-141200-

Mesoscale Precipitation Discussion 0036
NWS Weather Prediction Center College Park MD
916 PM EST Thu Feb 13 2025

Areas affected...Coastal Southern California...Foothills of the
SIerra

Concerning...Heavy rainfall...Flash flooding likely

Valid 140200Z - 141200Z

SUMMARY...The ongoing Atmospheric River event will continue into
the early hours of Saturday, with the threat of .50-.75"+ hourly
rainfall rates across portions of Southern California and into the
western upslope of the Sierra. Flash flooding will remain likely
across Southern California, especially across recent burn scar
areas, and possible in the foothills of the Sierra. The flash
flooding threat will be diminishing from west to east across
Southern California after 0200 UTC as a cold front moves steadily
east, but should perist to near 1200 UTC in the Sierra Foothills.

DISCUSSION...The latest GOES-W satellite imagery shows the broad
mid to upper level trof along the west coast pushing steadily
inland. An axis of anomalous PW values..2 to 2.5+ standard
deviations above the mean, and 850-700 mb moisture flux anomalies
of 3 to 5+ standard deviations above the mean, will continue on
the southeast side of this upper trof, along and ahead of the
associated cold front pushing steadily eastward across Southern
California this evening. Surface analysis at 0000 UTC indicates
this front having pushed to the southeast of Santa Barbara and
extending eastward just south of Sandburg and Edwards AFB.=20=20=20
There is good consensus in the latest hi res guidance on the
timing of the primary heavy rain areas in the vicinity of this=20
front pushing across Southern California this evening. HREF
neighborhood probabilities are high, 90%+, for hourly rain totals
of .50"+/hr along and ahead of the front, but drop to generally
less than 25% for 1"+/hr, reflective of the progressive nature of
this front. This progression will lead to a sharp cutoff in the
flash flood threat as the front passes. However, until this
occurs, flash flooding will remain likely across Southern
California, especially over recent burn scar regions.=20

..Foothills of the Sierra Nevada...
While the primary anomalous PW axis will remain across Southern
California this evening, persistent west southwesterly low level
upslope flow level will continue to impact the foothills of the
Sierra into early Saturday. HREF neighborhood probabilities for
.50"+/hr rainfall amounts are not as high or continuous as areas
across Southern California. but do depict potential for localized
heavy amounts and the potential for flash flooding issues.=20
Simulated hi res radars do show potential for cells to be much
slower moving and train in the upslope regions of the Sierra. In
areas of training, additional hourly amounts of .50-.75"+ and
additional totals of 2-3" are possible through early Saturday
morning.
=20

Oravec

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!89MFGru-sN9tQMcyudE5FAOdDpRlLChT9anMRUAZeQHCenuXZAVsnylGh7z6d0rV3Mh9= Cq58UMkl4T356xrp3V4SigM$ for graphic product...

ATTN...WFO...HNX...LOX...PSR...SGX...STO...VEF...

ATTN...RFC...CNRFC...NWC...

LAT...LON 39932145 39242074 38191983 38101991 37181925=20
36221856 35051825 34711787 34711774 34451696=20
34351684 33951639 32951616 32321669 33011746=20
33041754 33101769 33441803 33491825 33951871=20
34411857 35511890 36741990 37352017 38572095=20
39722147=20

=3D =3D =3D
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AWUS01 KWNH 150722
FFGMPD
TNZ000-KYZ000-ILZ000-MOZ000-ARZ000-151315-

Mesoscale Precipitation Discussion 0037
NWS Weather Prediction Center College Park MD
220 AM EST Sat Feb 15 2025

Areas affected...northeastern AR across MS Valley into KY and TN

Concerning...Heavy rainfall...Flash flooding possible

Valid 150717Z - 151315Z

SUMMARY...The threat for flash flooding will steadily increase
over the next 3-6 hours from northeastern AR, across the MS Valley
and into KY and TN. Training and repeating rounds of rain will
produce peak hourly rainfall of 0.5 to 1.5 inches and 6 hour
totals of 1 to 2 inches, locally as high as 3 inches.

DISCUSSION...Scattered showers and elevated thunderstorms were
observed to be increasing in coverage over portions of the lower
and middle MS Valleys in association with strong low level warm
air advection. 850 mb winds were from the S to SW, peaking around
70 kt in southern MO (per VAD wind data). Layered PW imagery
showed the rapid northward return of moisture from the eastern
half of TX into the lower MS Valley (surface to 700 mb layers),
allowing for the swift development of MUCAPE from west to east as
dewpoints in the lower layers of the troposphere increase,
allowing parcels to make use of relatively steep 700-500 mb lapse
rates (6-7 C/km).

Regional radar imagery at 07Z showed a persistent region of
elevated convection from northeastern AR into northwestern TN,
co-located with an axis of moisture flux convergence located at
the leading edge of low level moisture return. Alignment of this
axis and the mean steering flow from the WSW has caused training
and repeating rounds of heavy rain to affect portions of
northeastern AR into far northwestern TN. Local Wunderground
rainfall network observations have shown 0.3 to 0.6 inches of rain
within 30 minutes and one report as high as 0.7 inches in 30
minutes, just south of the MO Bootheel from ~06Z.

Expectations are for continued low level warm air advection to
maintain the trend of increasing MUCAPE values toward the east,
supporting elevated thunderstorms into central KY/TN later this
morning. RAP forecasts indicate little latitudinal movement of the
elevated zone of low level convergence over the next several hours
and additional upstream development is anticipated over AR in the
12-15Z window as forcing for ascent increases ahead of an
approaching shortwave trough axis which extended from the central
High Plains into the Desert Southwest at 07Z. Repeating rounds of
showers and thunderstorms will continue through the morning with
periodic episodes of training which will translate into locally
high rainfall rates.

Soil moisture across a large portion of the region is above
average due to recent rainfall and/or snow melt. As a result, FFG
values are low, with less than 2 inches in 3 hours along the KY/TN
border and less than 2.5 inches in 3 hours closer to the MS River.
While this MPD is tagged with flash flooding "possible", the
threat is only expected to increase over the region during the
daytime hours.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_LKzuenuFE5n5GFxs7T9W29CMESBylqN1j8oHhWN0qhcWfw7cdPyRqwFnLJlnpYxzdkU= PZuwZc4Uo9CGdNvPzJ_r8YM$ for graphic product...

ATTN...WFO...JKL...LMK...LZK...MEG...MRX...OHX...PAH...SGF...

ATTN...RFC...ABRFC...LMRFC...OHRFC...NWC...

LAT...LON 37398765 37278539 36858434 36188435 35808534=20
35518752 35158996 34769206 35459269 36329152=20
37068991=20

=3D =3D =3D
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AWUS01 KWNH 151332
FFGMPD
VAZ000-WVZ000-TNZ000-KYZ000-INZ000-MSZ000-MOZ000-ARZ000-151930-

Mesoscale Precipitation Discussion 0038
NWS Weather Prediction Center College Park MD
830 AM EST Sat Feb 15 2025

Areas affected...Portions of the OH/TN Valleys and Mid-South

Concerning...Heavy rainfall...Flash flooding likely

Valid 151330Z - 151930Z

SUMMARY...An expansive axis of heavy showers and thunderstorms
with strong cell-training concerns will be promoting a widespread
flash flood threat over the next several hours across portions of
the OH/TN Valley region and Mid-South.

DISCUSSION...The latest GOES-E IR satellite imagery shows an
expansive areas of heavy shower and thunderstorm activity
impacting areas of eastern AR up across central and western TN and
much of central and southern KY. Light to moderate stratiform
rains are noted north of here closer to the OH River and also into
the central Appalachians.

The convection that is organizing is associated with strong warm
air advection which is being aided by a powerful southwest
low-level jet of 50 to 60+ kts overrunning a strong frontal zone.
This is driving very strong moisture transport which is showing up
in an impressive fashion with the experimental CIRA-LVT (Layered
Vapor Transport) imagery as it is depicting SFC/850 layer LVT
magnitudes of 300+ kg/m/s. Meanwhile, a nose of MUCAPE values on
the order of 500 to 1000 J/kg is now oriented up across central to
northeast AR through western TN and western KY and this is helping
to facilitate the broader axis of elevated convection.

Over the next several hours, very strong warm air advection and
moisture transport will continue to support organizing bands of
convection that will be aligned with the deeper layer mean flow
and thus will be conducive for a substantial level of
cell-training. Increasing CAPE values with time along with
strengthening shear profiles will support stronger convective
elements that will yield increasingly heavy rainfall rates.

Rainfall rates with the stronger storms may reach as high as 1 to
1.5 inches/hour at least going through midday, but with
significant cell-training concerns, this may result in some
rainfall amounts by early afternoon alone of 2 to 4 inches. The
latest CAM guidance suggests areas of western/northern TN through
southern KY will have the heaviest totals going through the 18Z to
20Z time frame, with somewhat lesser amounts farther north.

Given the extremely sensitive/saturated soil conditions and
already elevated streamflows for many locations, these rainfall
totals over the next several hours are likely to begin resulting
in widespread flash flooding. Additional MPDs will be issued this
afternoon to update what should evolve into a high-impact and
life-threatening flash flood event in time.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9YBX9aJ4KgA8Z4iKzzTmNqcBfe8AW-uZDjSAoMlL6IbG7HtnQ7qDKHisENvc779BvUjO= SUH7voR82zaHIzanXz9Ys10$ for graphic product...

ATTN...WFO...JKL...LMK...LZK...MEG...MRX...OHX...PAH...RLX...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38438386 37938214 36958191 36258289 35938480=20
35578763 34359122 34619187 35219176 36318988=20
37208813 38008597=20

=3D =3D =3D
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AWUS01 KWNH 151701
FFGMPD
VAZ000-WVZ000-152300-

Mesoscale Precipitation Discussion 0039
NWS Weather Prediction Center College Park MD
1200 PM EST Sat Feb 15 2025

Areas affected...Central Appalachians and Portions of the VA
Piedmont

Concerning...Heavy rainfall...Flash flooding possible

Valid 151700Z - 152300Z

SUMMARY...Heavy rainfall moving into the central Appalachians and
adjacent areas of the VA Piedmont coupled with areas of melting
snow will set the stage for areal flooding and possible flash
flooding going through the afternoon hours.

DISCUSSION...The latest radar imagery shows moderate to heavy
rainfall along with locally some mixed precipitation that is in
the process of changing to rain advancing east across the central
Appalachians with southern WV and southwest VA seeing generally
the heaviest corridor of higher rainfall rates. The rainfall is
associated with strong warm air advection and moisture transport
into the region which is being aided by a southwest low-level jet
of 40 to 50 kts.

Instability is generally non-existent, but the level of isentropic
ascent and low-level frontogenetical forcing is quite strong and
is supporting rainfall rates of a 0.25" to 0.50"/hour. Meanwhile,
heavier rains are noted locally upstream over areas of central and
eastern KY which will be advancing eastward this afternoon, and
with an additional strengthening of the low-level jet expected
this afternoon, somewhat heavier rates that may exceed a
0.50"/hour will be possible over areas of southern WV down through
southwest VA. Some very modest intrusion of elevated instability
may arrive toward this evening that may also support a few
thunderstorms capable of producing these heavier rates.

The 12Z HREF guidance suggests additional rainfall amounts of as
much as 1 to 2+ inches by early this evening. These rains coupled
with warmer temperatures and a melting snowpack over some of the
higher terrain, and already high streamflows, will favor an
increasing concern for areal flooding and potentially some flash
flooding where these heavier rainfall rates can focus and persist.
Conditions will continue to be closely monitored over the next
several hours.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9CXcnsAJgEF_8dcauc9YTCzQK2Ukg73QSPRiGtp6YqQvqygLqPd4dqwi8v6lfNypQH5a= JsyKzLS8e6_RN0Yz9pC3E8A$ for graphic product...

ATTN...WFO...LWX...MRX...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 38808007 38567930 38127898 37597888 37007910=20
36707971 36598126 36708187 37698188 38258235=20
38578216 38798126=20

=3D =3D =3D
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AWUS01 KWNH 151856
FFGMPD
TNZ000-KYZ000-ILZ000-MSZ000-MOZ000-ARZ000-160055-

Mesoscale Precipitation Discussion 0040
NWS Weather Prediction Center College Park MD
155 PM EST Sat Feb 15 2025

Areas affected...Lower MS Valley into the Mid-South and OH Valley

Concerning...Heavy rainfall...Flash flooding likely

Valid 151855Z - 160055Z

SUMMARY...Flash flooding will become more expansive and
significant going into the early evening hours as heavy showers
and thunderstorms organize and train over the same area. Some of
the flash flooding is expected to be extremely dangerous and
life-threatening.

DISCUSSION...Strong shortwave energy ejecting east out across the
southern Plains will be encroaching on the Lower MS Valley this
afternoon and will be interacting with a moist and increasingly
unstable airmass which coupled with strengthening shear profiles
will set the stage for expanding clusters of strong to severe
thunderstorms. This is likely to include a combination of
multicell and supercell convection which will be embedded within
an environment conducive for yielding very heavy rainfall rates.

GOES-E visible satellite imagery shows a notable increase in cloud
street activity across LA/MS and through central and southern AR
which is indicative of an increasingly unstable boundary layer.
Diurnal heating via solar insolation has allowed for MLCAPE values
to increase to 1000 to 1500 J/kg, and these values will continue
to increase over the next few hours. A quasi-stationary front is
draped from the Arklatex northeastward into northern MS and far
southwest TN with multiple waves of low pressure noted along it.
Meanwhile, a powerful southwest low-level jet is in place reaching
upwards of 50 to 60+ kts and this is yielding very strong moisture
transport from the Gulf of America up across the broader Lower MS
Valley and Mid-South region with PWs that have now increased to
1.3 to 1.5 inches.

As thunderstorms continue to develop and organize over the next
several hours, there will be rainfall rates capable of reaching
1.5 to 2 inches/hour with the stronger cells. Cell-merger and
cell-training concerns will increase by later this afternoon and
this evening with potentially some QLCS-related training of storms
possible in the 21Z to 00Z time frame from south-central to
northeast AR into the MO Bootheel, northwest TN and far southwest
KY. This is favored by a consensus of the 12Z HREF and the 16Z to
18Z runs of the experimental WoFS guidance which shows a
combination of multicell, supercell and QLCS-driven convection
heading into the evening hours.

Additional rainfall amounts of as much as 3 to 6 inches are
expected within the corridors of greatest cell-training which
currently is being most favored across northeast AR into the MO
Bootheel, northwest TN and far southwest KY going through 00Z.
Given that some of these areas already have flash flooding
ongoing, the additional rains are likely to foster extremely
dangerous and life-threatening flash flooding conditions by this
evening, with Flash Flood Emergency level impacts possible. As
conditions evolve this evening, additional MPDs will be issued to
address this high-impact event.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5sDaEqb8kaaqOtjNqI9qjq4Zfoa4R4X76DNCTY7jrCBOcSZPwnFV4Z8bjoJSYUeH8OqW= QlIa7Da_Ddzeh7AkvK07zns$ for graphic product...

ATTN...WFO...LMK...LZK...MEG...OHX...PAH...SGF...SHV...

ATTN...RFC...ABRFC...LMRFC...OHRFC...NWC...

LAT...LON 37798645 37448527 36658564 36088783 34629061=20
33119252 33099332 33889348 35589251 36809080=20
37528852=20

=3D =3D =3D
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AWUS01 KWNH 151947
FFGMPD
VAZ000-WVZ000-OHZ000-TNZ000-KYZ000-INZ000-160145-

Mesoscale Precipitation Discussion 0041
NWS Weather Prediction Center College Park MD
246 PM EST Sat Feb 15 2025

Areas affected...Portions of the OH/TN Valleys and Central
Appalachians

Concerning...Heavy rainfall...Flash flooding likely

Valid 151945Z - 160145Z

SUMMARY...Locally significant flash flooding is expected going
into the evening hours from persistent heavy rainfall over
saturated soils.

DISCUSSION...The latest GOES-E IR satellite imagery along with
dual-pol radar shows an expansive area of heavy rain continuing to
advance west to east across central and eastern KY and into
southwest VA and southern WV. The activity continues to be
associated with strong warm air advection which is being aided by
a powerful southwest low-level jet of 40 to 60+ kts overrunning a
strong frontal zone.

This is driving very strong moisture transport with magnitudes in
the SFC/850 mb layer of as much as 320 kg/m/s aiming across much
of western and central TN and toward southern KY as seen in the
experimental CIRA-LVT (Layered Vapor Transport) imagery. Some very
modest instability with MUCAPE values of as much as 100 to 250
J/kg is noted over the region and this has been supporting some
occasional elevated convective elements.

Over the next several hours heading into the evening, there will
continue to be a west to east axis of heavy rainfall given the
level of strong isentropic ascent and frontogenetical forcing, but
as a warm front lifts north with time, this band of heavy rainfall
should also gain latitude with the rain eventually getting into
more of north-central to northeast KY and central WV.

The rainfall rates should be able to at least occasionally reach
into the 0.50" to 0.75"/hour range, and especially with any
stronger convective elements that continue to materialize. These
rates and overall persistence of heavy rainfall should support
additional rainfall totals by early this evening of 1 to 2 inches
with locally higher amounts.

Many areas have ongoing areal flooding and flash flooding, and
with extremely sensitive/saturated soil conditions and very high
streamflows, much of the additional rainfall will lead to
immediate runoff and potentially support significant flash
flooding for some locations. This will include areas of the
central Appalachians for locations that currently also have a
melting snowpack and thus added water runoff concerns.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_x0dK2JV4HgGIM65ux75coVlDb0zP0EKlMSOCYp6OUxNID4h2UFh_3Lze1FX9vfrroeP= NMzW9UPAY6yLbhgB4ivmMHs$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...LWX...MRX...OHX...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 38868096 38507991 38007962 37197993 36698093=20
36348411 36568591 37358642 37988611 38578432=20
38848255=20

=3D =3D =3D
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AWUS01 KWNH 160046
FFGMPD
OHZ000-TNZ000-KYZ000-INZ000-ILZ000-MSZ000-MOZ000-ARZ000-160645-

Mesoscale Precipitation Discussion 0042
NWS Weather Prediction Center College Park MD
745 PM EST Sat Feb 15 2025

Areas affected...Lower MS Valley into the Mid-South and OH Valley

Concerning...Heavy rainfall...Flash flooding likely

Valid 160045Z - 160645Z

SUMMARY...Widespread flash flooding with damaging and
life-threatening impacts will continue as showers and
thunderstorms continue to train locally over the same area and
focus heavy rainfall totals.

DISCUSSION...The latest GOES-E IR satellite imagery along with
dual-pol radar shows widespread and well-organized showers and
thunderstorms impacting much of the Lower MS Valley with a
northeastward extension up across portions of the Mid-South and
the OH Valley. Strong shortwave energy is crossing the Arklatex
and will be rapidly lifting northeastward into the OH Valley
overnight. As it does so, the energy will be interacting with a
moist and moderately buoyant airmass continuing to surge
northeastward from the Lower MS Valley.

This airmass is characterized by MUCAPE values of as much as 1000
to 1500 J/kg and PWs approaching 1.5 inches which is also being
aided by the persistence of a powerful 50 to 60+ kt southwest
low-level jet. Radar imagery shows a QLCS currently evolving from
eastern AR up across western TN and western KY with some embedded
supercell convection. The better thermodynamics are situated from
southeast AR through northern MS and into western TN and this
should provide convective sustenance through the remainder of the
evening hours as the overall QLCS activity advances off to the
east.

While the southern flank of the overall convective footprint this
evening should become increasingly progressive as a cold front
arrives from the west, there will still be notable concerns for
training showers and thunderstorms for several more hours farther
off to the northeast in close vicinity of a warm front lifting
north through the OH Valley.

Rainfall rates with the stronger storms over the next several
hours will still be capable of reaching 1.5 to 2 inches/hour with
the strongest of cells. Additional rainfall amounts going through
06Z may reach as high as 2 to 4 inches with isolated heavier
amounts not out of the question.

Many areas have already received 2 to 4 inches of rain since early
this morning, and the extremely sensitive ground conditions with
saturated soils and ongoing widespread areas of flash flooding
coupled with the additional rainfall, will pose concerns for
potentially Flash Flood Emergency level impacts with damaging and life-threatening conditions. This situation will continue to be
closely monitored.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-u7CK8MFFfh285T7L6vQEdWwmFqgQ4JozDgaBI4lhPBu2Yio0WTPIyifjGyhjkKWHNON= Qc75AzU5U893xOknW4FalYw$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...LZK...MEG...MRX...OHX...PAH...
RLX...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38918407 38398319 37498313 36788408 36358516=20
35508719 34558970 34249121 34669174 35549119=20
36728984 37428858 38068736 38868545=20

=3D =3D =3D
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AWUS01 KWNH 160121
FFGMPD
TNZ000-ALZ000-MSZ000-LAZ000-ARZ000-160720-

Mesoscale Precipitation Discussion 0043
NWS Weather Prediction Center College Park MD
820 PM EST Sat Feb 15 2025

Areas affected...Northern LA...Central and Northern MS...Western
and Northern AL...Middle TN

Concerning...Heavy rainfall...Flash flooding possible

Valid 160120Z - 160720Z

SUMMARY...Heavy showers and thunderstorms will be sweeping across
the region over the next several hours which may produce some
areas of flash flooding, with especially the more urbanized
locations at risk for potential runoff problems.

DISCUSSION...Radar and satellite imagery shows an evolving QLCS
crossing through areas of eastern AR through western TN, with more
broken clusters of organized convection including a few supercells
down across areas of northern LA which is beginning to move into
areas of western MS.

The airmass downstream of the current convection is moist and
moderately buoyant with MLCAPE values of 1000 to 1500 J/kg locally
and PWs of near 1.5 inches. However, a substantial amount of shear
remains in place ahead of the strong shortwave and attendant
frontal system crossing the Lower MS Valley. A very strong
low-level jet of 50 to 60+ kts remains a key player in driving
enhanced moisture/instability transport and this will sustain the
convective threat well into the overnight hours as a cold front
approaches and eventually crosses the region.

Rainfall rates associated with the QLCS and more discrete
supercell activity over the next several hours will likely reach
as high as 1.5 to 2 inches/hour, and there may be at least some
occasional cell-merger and cell-training activity that will
support some locally excessive rainfall totals that may reach 2 to
4 inches.

NASA SPoRT data shows antecedent soil conditions on the moist side
across much of the region given the heavy rainfall that occurred a
few days ago. This coupled with the locally heavy convective rains
over the next several hours may pose at least some concern for
areas of flash flooding. However, generally the more urbanized
locations will be at greatest risk for runoff problems and impacts
heading into the overnight hours.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_dh-UctBjAzaR5XuVslTA7kCWT2U17Uy4b4tnD0KR7Ikw5OL3TSB6yB3TtpYwMlaiFlY= TmhjBMfPKLhR7eOGB3-TFn0$ for graphic product...

ATTN...WFO...BMX...HUN...JAN...LCH...LIX...LZK...MEG...MRX...
OHX...SHV...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON 36018588 35688528 34408623 32918779 31708932=20
31109076 31149210 31389265 31909290 32679249=20
33559157 34289031 35008825=20

=3D =3D =3D
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AWUS01 KWNH 160202
FFGMPD
PAZ000-MDZ000-VAZ000-WVZ000-OHZ000-KYZ000-160800-

Mesoscale Precipitation Discussion 0044
NWS Weather Prediction Center College Park MD
901 PM EST Sat Feb 15 2025

Areas affected...Portions of the OH Valley and Central
Appalachians

Concerning...Heavy rainfall...Flash flooding likely

Valid 160200Z - 160800Z

SUMMARY...Locally significant and life-threatening flash flooding
will continue into the overnight hours with additional Flash Flood
Emergency level impacts possible from additional rounds of heavy
rainfall, with the central Appalachians continuing to see the
greatest risk of this.

DISCUSSION...The latest radar imagery continues to show an
expansive area of heavy rainfall impacting areas of mainly
north-central to northeast KY through central WV and down into
areas of south-central VA. The activity continues to be associated
with strong warm air advection which is being aided by a powerful
southwest low-level jet of 40 to 60+ kts surging up through the
OH/TN Valley region and into the central Appalachians.

Very strong transport continues as a result which coupled with
enhanced isentropic ascent and frontogenetical forcing continue to
yield heavy rainfall rates generally in the 0.25" to 0.50"/hour
range with some occasionally heavier rates where some embedded
elevated convective elements focus. Some very modest instability
with MUCAPE values of as much as 100 to 250 J/kg is noted over the
region and this continues to favor at least some transient pockets
of convection.

A warm front continues to gradually lift north into the OH Valley
and central Appalachians and this is allowing for the overall
heavy rainfall shield to gain latitude. Going into the overnight
hours, rainfall rates should still be capable of reaching a
0.50+"/hour locally and especially with the aforementioned pockets
of elevated convection. Additional rains of as much as 1 to 2
inches will be possible over the next 6 hours, with areas closer
to the OH River involving northeast KY and southern OH seeing
potentially 2 to 3 inches given heavier rainfall approaching from
western KY including some stronger pockets of even stronger
convection.

Given the additional rainfall and ongoing widespread focus of
areal flooding and flash flooding, significant and
life-threatening flash flooding is likely to continue with
additional potential for Flash Flood Emergency level impacts. This
will especially be the case over portions of the central
Appalachians where there have already been a total of 4 Flash
Flood Emergencies issued since early this afternoon.
Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Fg8Ag0Kz6_p6CldtRGTmShLNnTzxgtRFgJQKMCYiQiuItEFTm3kwmTWjaghChzH9c0f= cMRalbMI6zKUo33LWwfq1OI$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 39878106 39677973 39037917 38167920 37658001=20
37598196 37648310 37888390 38408422 39038417=20
39528328 39768232=20

=3D =3D =3D
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AWUS01 KWNH 160432
FFGMPD
PAZ000-WVZ000-OHZ000-KYZ000-INZ000-161000-

Mesoscale Precipitation Discussion 0045
NWS Weather Prediction Center College Park MD
1132 PM EST Sat Feb 15 2025

Areas affected...southwestern to eastern OH into western PA

Concerning...Heavy rainfall...Flash flooding possible

Valid 160430Z - 161000Z

SUMMARY...Localized flash flooding will be possible from portions
of southwestern OH into eastern OH and western PA through 10Z.
Peak rainfall rates between 0.50 and 0.75 in/hr may occur but most
locations should see lower rates. Still, the addition of 1-2
inches of rain over a relatively short period of time atop
sensitive ground conditions may result in localized flash flooding.

DISCUSSION...Regional radar imagery at 04Z depicted an area of
higher reflectivity moving east-northeastward into
southwestern/central OH, just north of MPDs #42 and #44. While
bright banding accounts for these higher reflectivity values with
surface temperatures only in the 30s and 40s, ground observations
have reported peak rainfall rates of about 0.25 to 0.50 inches
(locally higher) to the west and north of Cincinnati within the
last hour. This axis of precipitation is related to a
strengthening zone of low level frontogenesis (850-700 mb),
located north of an approaching surface low in KY, connected to a quasi-stationary front that extended through eastern KY into
north-central WV. SPC mesoanalysis data from 04Z indicated less
than 100 J/kg MUCAPE to the north of the front into OH. Strong
divergence aloft was also present over the region, given the
position of a 180+ kt upper level jet max located over MI and Lake
Huron, placing OH within its favorable right-entrance region.

Short term RAP forecasts indicate the surface low over KY will
steadily track northeastward over the next several hours, allowing
the front to lift north as a warm front through 09Z. This movement
will cause the strong axis of frontogenesis to also lift north
while weak MUCAPE (up to 150 J/kg or so) moves into southeastern
OH and western PA between 06-09Z. Bands of heavy rain are expected
within the broader precipitation shield with occasional rates as
high as 0.50 to 0.75 in/hr. Additional rainfall of 1 to 2 inches
is expected to occur through 10Z from southwestern OH into eastern
OH and western PA. While this region of the Midwest has escaped
the ongoing significant rains and flooding to the south, soils
remain sensitive with low FFG values of only 1 inch in 3 hours
across the upper OH Valley. Localized flash flooding may result
due to an additional 1-2 inches of rain over a fairly short period
of time.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7BAiGOy8kEX0Z4HBYlIicO-KDRnqegYnHBg7SBqOeCHPk2w6XUgTeWNieeac3ajxg3Uv= trfZBU7hi5iGPucbXayZgAw$ for graphic product...

ATTN...WFO...CLE...CTP...ILN...PBZ...RLX...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 41607951 41217861 40217943 39797989 39858054=20
39788209 39048425 38888491 39668496 40678319=20
41268145=20

=3D =3D =3D
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AWUS01 KWNH 160641
FFGMPD
VAZ000-NCZ000-WVZ000-TNZ000-KYZ000-161230-

Mesoscale Precipitation Discussion 0046
NWS Weather Prediction Center College Park MD
140 AM EST Sun Feb 16 2025

Areas affected...Cumberland Plateau into central Appalachians

Concerning...Heavy rainfall...Flash flooding likely

Valid 160639Z - 161230Z

SUMMARY...Despite an expected weakening trend in rainfall
intensity, additional rainfall over a 2-3 hour window will impact
locations of the central Appalachians hard hit on Saturday. Up to
an inch of rain is expected in some locations with rates of 0.25
to 0.5 in/hr. These rains are expected to exacerbate ongoing
flooding concerns.

DISCUSSION...0630Z radar imagery showed that a squall line
extended SSW from southern TN (between I-65 and I-24) into
northwestern AL. An inflection along the line was noted over
southern TN with an inferred low level vorticity max to its west.
North of the inflection point, the convective line was weaker but
still has had a history of producing hourly rainfall in excess of
1 inch over Middle TN since 04Z. The convective line has begun to
outpace many of the 00Z hires models, most notably over AL, likely
not properly capturing the influence of the mesoscale vorticity
max.

Going forward, instability will be a limiting factor to higher
rainfall rate potential across the "northern" locations of eastern
KY, southern WV and western VA. However, recent hires models may
be slightly downplaying rainfall rate potential from the
Cumberland Plateau into the central Appalachians. Current thinking
is that 0.25 to 0.50 in/hr will be possible from eastern KY into
southern WV and western VA with locally higher rates farther south
over eastern TN where up to a couple hundred J/kg of CAPE may be
present to locally boost rainfall intensity. However, heavy
rainfall duration will be limited by the progressive movement of
the convective line across TN.

Farther north into eastern KY, southern WV and western VA, poorer
organization of the line will be somewhat offset by a longer
duration of rainfall, about 2-3 hours is when a majority of the
expected rainfall will fall. Portions of this region have received
heavy rainfall over the past 24 hours and have ongoing/widespread
significant flooding. Up to an additional inch of rain may fall
across these sensitive locations which will act to exacerbate
existing flooding concerns.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4tfc1TY4BPoPr3mT0SExna_-HdVTbXyjJ7Lx8pDjG2Kd9NnJHBU1PtteAsY_pIjgmpr_= j5g0qjkAmSOkRRfFrLxPxJQ$ for graphic product...

ATTN...WFO...JKL...MRX...OHX...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 38398034 38327990 37977999 37388020 36928005=20
36508149 36288219 35728344 35498470 35698554=20
36188547 36918424 37558322 37988274 38278199=20
38368112=20

=3D =3D =3D
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AWUS01 KWNH 160733
FFGMPD
PAZ000-WVZ000-OHZ000-KYZ000-INZ000-161030-

Mesoscale Precipitation Discussion 0047
NWS Weather Prediction Center College Park MD
233 AM EST Sun Feb 16 2025

Areas affected...upper OH Valley

Concerning...Heavy rainfall...Flash flooding likely

Valid 160730Z - 161030Z

SUMMARY...Moderate to heavy rain will continue to translate east
through the upper OH Valley in the short term with an additional
inch of rain through 1030Z. Renewed flash flooding is expected.

DISCUSSION...0730Z radar imagery showed a leading linear segment
of heavy rain moving through eastern KY, followed by a stratiform
region of moderate to heavy rain over eastern KY. As a low level
vorticity max advances northeast from Middle TN, an 2-3 hour long
duration of stratiform moderate to heavy rain is expected to
advance into eastern KY, southern OH and eventually portions of
western WV. In addition, preceding the stratiform region will be a
leading line of showers with embedded thunderstorms which have had
a history of 0.25 to 0.50 in an hour but with a 0.25 inch or more
in 15 minutes over eastern KY.

As the entire envelope of rain translates toward the
east/northeast, additional totals up to about an inch are expected
through 1030Z, with a likelihood of renewed flash flooding or a continued/worsening of ongoing flooding concerns occurring from
heavy rain which fell over the past 24 hours.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6BP8PzyRHNEKpvsqNiFF7Yyyibfz9nGkUd5w_1SazcpiI6Buo5H2cC0t0gEgqrf8pdsJ= SNCWbBtxqXXKNUUPknncq0Q$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...PBZ...RLX...

ATTN...RFC...OHRFC...NWC...

LAT...LON 40038127 39908038 39558035 39178062 38228193=20
37628302 36958397 36798457 36938503 37448531=20
38198528 39078473 39758323 39958210=20

=3D =3D =3D
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AWUS01 KWNH 222021
FFGMPD
CAZ000-ORZ000-WAZ000-230820-

Mesoscale Precipitation Discussion 0048
NWS Weather Prediction Center College Park MD
320 PM EST Sat Feb 22 2025

Areas affected...Pacific Northwest

Concerning...Heavy rainfall

Valid 222020Z - 230820Z

SUMMARY...Atmospheric river conditions arriving across the Pacific
Northwest will bring heavy rainfall in across the coastal ranges
and into the windward slopes of the Cascades later today and
tonight.

DISCUSSION...A series of offshore shortwave impulses lifting
northeastward toward British Columbia over the next 6 to 12 hours
will be bringing an offshore frontal system toward the coastal
ranges of western WA and western OR along with strong atmospheric
river conditions.

The latest GOES-W WV suite along with CIRA-ALPW and experimental
LVT data shows a very well-defined trans-Pacific fetch of deep
moisture extending from just offshore of the Pacific Northwest
southwestward all the way down to northwest of Hawaii with notable
tropical origins of some of the moisture transport. Multiple
low-amplitude shortwave impulses are embedded within this
atmospheric river channel, and this will help to facilitate strong
warm air advection and onshore flow into especially the coastal
ranges of western WA and western OR along with the windward slopes
of the Cascades by later today and continuing into the overnight
period that will drive locally enhanced rainfall amounts.

PW anomalies are forecast to rise to 2 to 3+ standard deviations
above the climatological mean by 00Z and continue at this level
through tonight as a strong southwest low to mid-level jet sets up
and persists just offshore and overruns the higher terrain of the
Pacific Northwest. In fact, the 850/700mb moisture flux anomalies
are forecast to rise to as much as 3 to 5+ standard deviations
above normal, with one peak this evening by around 00Z and then
another later tonight as the arrival of each shortwave impulse
corresponds to a stronger low to mid-level wind field.

Given the enhanced deep layer warm air advection and moisture
transport along with some of its tropical origin, the rainfall
rates are expected to be efficiently high. The 12Z HREF guidance
shows high probabilities of seeing 0.50" to 0.75"/hour rainfall
rates across the Olympic Peninsula in the 21Z to 00Z time frame,
with portions of the southwest WA coastal range also seeing
elevated probabilities of these rates toward early this evening.
Areas farther east into the windward slopes of the Cascades and
farther south across coastal OR and gradually coastal northwest CA
should see rates easily reach into the 0.25" to 0.50"/hour range
with rates occasionally over a 0.50"/hour.

Over the next 12 hours, some rainfall totals are expected to reach
as high as 3 to 5+ inches over the higher terrain and especially
the favored coastal ranges and upslope areas of the Cascades with
lesser amounts over the adjacent interior valleys/terrain-shadowed
locations. Generally these initial rains are not likely to cause
much in the way of any flooding threat aside from potentially some
localized urban and small stream runoff concerns where the heavier
and more persistent rates set up. However, additional heavy
rainfall beyond this period going into Sunday will gradually raise
the flooding threat.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-Bcn8atyisx4Hf-E9XQot4K2cLaj04bBNcljUCuWosTXrq0j5Uxuq4UDLpO2N8fDN-3m= XFr0k6riV0DfUzAGFmmzU_c$ for graphic product...

ATTN...WFO...EKA...MFR...OTX...PDT...PQR...SEW...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 49162120 48902067 48122052 47472075 47002120=20
46402119 45762157 45192153 44712176 44052168=20
43342208 42402211 42282262 42932320 42792371=20
42262360 41472341 40742345 40022393 40282454=20
41532441 43062470 44952423 46622433 47972464=20
48332411 48092348 47562304 47682238 48692234=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 230754
FFGMPD
IDZ000-CAZ000-ORZ000-WAZ000-231800-

Mesoscale Precipitation Discussion 0049
NWS Weather Prediction Center College Park MD
253 AM EST Sun Feb 23 2025

Areas affected...Coastal and Cascade Ranges of S WA, OR & Far
Northwest CA & E WA/SE OR/N ID...

Concerning...Heavy rainfall

Valid 230800Z - 231800Z

SUMMARY...Prolonged AR continues but very broad plume of moisture
will start to focus ahead of next stronger cyclone/frontal push
toward 18z. Deep moisture surges through the Columbia Plateau
into E WA/N ID prepping the soils/increasing run-off ahead of next
surge.

DISCUSSION...GOES-W WV suite shows broad cirrus canopy associated
with polar jet streak and deep atmospheric river extending from
the eastern Pacific across W WA into S British Columbia into the
entrance of the core jet streak that is about 150-160kts. The weakening/initial low level cyclone has occluded northward into
the central BC coastal region with the front extending southward
into/near the Cascade Range, while the warm front extends through
the Columbia River Valley. CIRA LPW, particularly the sfc-850mb
layer bares this evolution out very well with the cold front
starting to sag/stall SW to NE just across the W WA angling back
toward the next approaching stronger wave out near 150W. The
plume remains very broad/wide from the W WA coast to the
Lost/Redwood coast of northwest California with a solid slug of
850-500mb centered on the NW Oregon coast extending back toward
37-38N and 140W; both layers showing associated moisture flux
values running well into 99th percentile for the 20 year record.=20
As such, 1.25" TPW values intersect much of the coastline with
weakly confluent 850-700mb flow angled from the SW about 30
degrees off perpendicular, but given the depth has washed over the
coastal range to to the Cascades. Still, within a broad ascent
pattern in the exiting right entrance pattern provides a
continuation of moderate rainfall rates of .25-.3"/hr, slowly
reducing from north to south across the WA Cascades through the
early morning (but remaining solid further south across OR). This
should result in 2-4" totals across the coastal and Cascade ranges
of Oregon to 18z; with 1.5-2.5" across WA early through 15z.

...Eastern Washington/N Idaho...
As noted above, the broad plume is broad and deep enough to wash
over the coastal range and has begun to fill the Columbia river
Valley into the Plateau region. IVT values of 300-400 kg/m/s will
increase to near 500-600 kg/m/s along 30-45kts of gap flow through
the Plateau into the foothills and eventually higher terrain of SW
WA/NE OR and then toward the Clearwater Range by 12z. Total PWat
values are starting to increase above .75" which would place 90+th
percentile moisture for the date at OTX and GFS/ECMWF flux values
at 3-5 standard anomaly values across the area. While total
moisture is much less than coastal positions, rates of .15-.2" may
occasionally reach .25"/hr with steadily increasing freezing
levels with all but the highest peaks along the ID/MT boarder and
further south across the Blue/Wallowa and Salmon River Ranges
likely to experience more rain than snow/wintry mix. As such
spots of 1-2" totals are expected by 18z. Given the rates are low
and prolonged, this will more likely pre-soak the soils with
slowly increasing run-off values with this particular surge of
moisture...but there is more to come that may be more likely to
result in localized flooding concerns.

...Southwest Oregon/Northwest California...
As the jet streak exits the broader wave of deep moisture will
remained focused across much of OR into NW CA. As the trailing
edge to the prior forcing backs ahead of the next stronger
approaching shortwave/developing low level cyclone/pressure trough
toward 18z, westerly winds will increase into the 45-50kt range
becoming ever so slightly more orthogonal to the boreal rain
forests of SW OR/NW CA. IVT values over 700 kg/m/s combined with
slightly steeper orography will allow for rain-rates to exceed
.5"/hr, occasionally reaching .75"/hr starting around 09-10z.=20
This will be prolonged for about 6-9hrs and potentially result in
localized spots of 4-6". This is not atypical for these
rain-forests but still strong enough for increased run-off and low
end flooding potential before the core of the narrowing AR plume
starts to shift northward with strengthening warm air advection
after 15z.=20

There will remain some timing/uncertainty to the width of the core
of the heavy rainfall surge toward 18z and a subsequent MPD will
be required at that time to provide additional details for the
main surge of heaviest rainfall/highest impacts to this longer
duration AR event.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7owdNXCQ66se1jmlJbzZ-zMyLYjnzALvV8uQUYrQ9mpQtR3nsZjcZBrTRdwd0abJF_5m= 4ApWn2jy_KJ6iZZehzfp6xA$ for graphic product...

ATTN...WFO...EKA...MFR...MSO...OTX...PDT...PQR...SEW...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 48291746 48071637 47651595 46901558 46161514=20
45641539 45411657 45271772 45431937 45052090=20
44302149 42912179 42092223 41482268 40702308=20
40742421 41462419 42772465 43782437 44932423=20
45852415 46742425 47082388 46662330 46602249=20
47772185 47952108 46582112 46142070 46221911=20
47281863 47891828=20

=3D =3D =3D
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AWUS01 KWNH 231827
FFGMPD
CAZ000-ORZ000-WAZ000-240625-

Mesoscale Precipitation Discussion 0050
NWS Weather Prediction Center College Park MD
125 PM EST Sun Feb 23 2025

Areas affected...Pacific Northwest

Concerning...Heavy rainfall

Valid 231825Z - 240625Z

SUMMARY...An atmospheric river resurgence this afternoon and
evening will bring a new round of heavy rainfall to the Pacific
Northwest and especially for the coastal ranges and windward
slopes of the Cascades.

DISCUSSION...The latest GOES-W WV suite shows a negatively tilted
upper-level trough in between 40-50N and approaching 130W with an
occluded low center near 48N 142W. This energy will gradually
advance off to the northeast toward the Pacific Northwest and
British Columbia over the next 6 to 12 hours which will bring a
resurgence of stronger atmospheric river conditions back across
the region this afternoon through this evening.

A warm front that is currently oriented west to east across the
Columbia River basin will lift back northward with time as a
strong low to mid-level jet surges northeastward ahead of the
approaching offshore surface low and upper-level trough axis. This
will bring a resurgence of strong warm air advection and moisture
transport into the coastal ranges from far northwest CA up across
western OR and western WA through this evening.

IVT magnitudes are already increasing again across coastal
northwest CA and much of western OR and will be well into the 600
to 800+ kg/m/s range this afternoon through early this evening as
the offshore cold front approaches the region. These IVT values
will increase up across western WA as well, with magnitudes here
generally rising back as high as 400 to 600 kg/m/s.

PW anomalies of 2 to 3+ standard deviations above normal are
forecast through this evening ahead of the cold front and this
coupled with 850/700 mb moisture flux anomalies of 3 to 5+
standard deviations above normal should favor rainfall rates
reaching as high as 0.50" to 0.75"/hour. The heaviest rates should
tend to be focused across the OR coastal ranges and there is some
low-end potential for rates to even approach 1.0"/hour with
arrival of the strongest IVT parameters and forcing later this
afternoon. Enhanced IVT spillover into the windward slopes of the
Cascades should support at least spotty areas of a 0.50" to
0.75"/hour rates here, but the rates overall should tend to be
somewhat more modest farther north into western WA with lower IVT
values and lower PWs by comparison to western OR.

A cold front will advance inland by late this evening and this
will then allow for another break in the overall atmospheric
regime with rates once again then coming back down. However, at
least over the next 6 to 12 hours, expect additional rainfall
amounts of as much as 2 to 4 inches for western OR and 1 to 3
inches for western WA. These rains may bring additional concerns
regionally for runoff problems including small stream and urban
flooding.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!93hHJZr0qetLo277TEuzyb-znKxZjhbG7rVHDOjABuldxUbC_x0FdY6w5DyCIQ6HRfAU= tj3FZEQvAuW0v1Bzdcj-ImY$ for graphic product...

ATTN...WFO...EKA...MFR...OTX...PDT...PQR...SEW...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 49162120 48902067 48362056 47722062 47212097=20
46512092 46222066 45892047 45722076 45502126=20
45052150 44542152 43992163 43622194 42852201=20
42442228 42462303 42222342 41652354 41792441=20
43062470 44172437 46192417 47572457 48052414=20
48012332 47762313 47512270 47632198 48432212=20
49032186=20

=3D =3D =3D
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