FOUS11 KWBC 150714
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
314 AM EDT Fri Mar 15 2024

Valid 12Z Fri Mar 15 2024 - 12Z Mon Mar 18 2024

...Southern Rockies, Four Corners, and the Southwest...
Days 1-3...

***Heavy snow wanes along the Front Range but continues across the
Four Corners through the weekend***

The impressive snow event across the Front Range due to long-
duration and robust upslope flow will begin to wind down today as
the best ascent shifts southward, and mid-level flow begins to
return to the south. This should bring a slow end to the upslope
component of this event, although this will be at the expense of a
larger scale event which begins in earnest across the Four
Corners. Additional snow in the Front Range and Sangre de Cristos
D1 only has a 30-60% chance of exceeding an additional 4 inches.

Meanwhile, as precipitation across the Front Range begins to wane,
the parent upper low sinking south towards the Desert Southwest
will begin to exert its influence across the region. The deep low
with height anomalies nearing -3 sigma according to NAEFS will
spread pronounced and long-lasting mid-level divergence downstream
from the lower CO Basin through the Central High Plains. Confluent
flow southeast of this low will help surge moisture northward,
combining with modest jet-level diffluence to expand moderate to
heavy precipitation through Saturday. This will result in heavy
snowfall in much of the terrain from the Mogollon Rim and Kaibab
Plateau eastward into the Wasatch, San Juans, and Sangre de
Cristos, with heavy snow accumulations likely above snow levels of
6000-8000 ft in the region of strongest WAA/heaviest precip, but
may fall to 4000-5000 ft beneath the cold core low, especially as
it begins to eject east by Sunday. WPC probabilities for more than
6 inches D1 are above 90% in the southern Wasatch and much of the
San Juans, as well as the higher terrain of the Mogollon Rim, and
White Mountains, with additional low to moderate probabilities
(20-60%) fore 6+ additional inches on D2 across much of the same
area.

As the upper low finally begins to fill and eject eastward through
the Four Corners on Sunday, total forcing for ascent and moisture
should begin to wane. However, still sufficient moisture and
persistent ascent both due to height falls and steepening lapse
rates aloft will allow for precip falling as snow to continue to
pivot eastward, primarily falling in the San Juans and Sangre de
Cristos D3. Additional snowfall D3 is confined to the San Juans and
Sangre de Cristos, where WPC probabilities for 6+ inches are again
20-40%. 3-day snowfall in some of the higher terrain of the Wasatch
and San Juans will likely reach 2-3 feet.


...Great Lakes and New England...
Day 3...

A surface low pressure moving through Ontario and Quebec will drive
a cold front through the Great Lakes, Ohio Valley, and into New
England. Some modest moist advection will occur downstream and
ahead of this front resulting in a narrow corridor of heavy
precipitation lifting northeast into New England on Sunday. Much of
this will likely fall as rain in the marginally favorable thermal
structure of the column, but across northern NH and into northern
ME, especially in higher elevations, WPC probabilities for more
than 4 inches of snow are 10-30%.

More impressive, although still somewhat modest, is likely to be an
increase in lake effect snow (LES) behind the front as strong CAA
surges southeast across the Great Lakes. This will result in axes
of significant snowfall accumulations in the favored N/NW snow
belts across the U.P. of MI, and along the Chautauqua Ridge and
Tug Hill Plateau. WPC probabilities within the LES bands are as
high as 20-30% downwind of Lakes Superior, Erie, and Ontario,
highest across the U.P. of MI.


The probability of receiving at least 0.1" ice is less than 10%
across the CONUS through Day 3.

Weiss


**Key Messages for the March 13-16 Winter Storm can be found on our
website at https://www.wpc.ncep.noaa.gov **


$$
--- SBBSecho 3.20-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)