ACUS48 KWNS 060845
SWOD48
SPC AC 060843
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0343 AM CDT Sat Jun 06 2026
Valid 091200Z - 141200Z
...DISCUSSION...
...Day4/Tuesday...
Latest model guidance remains in good agreement in depicting the
progression of a short-wave trough and associated mid/upper-level
jet streaks into the northern High Plains Tuesday afternoon and
evening, with downstream height falls overspreading the Dakotas. At
the surface, a lee cyclone over eastern MT Tuesday afternoon is
expected to develop north-northeast through western ND, while a
trailing cold front edges east into the western Dakotas.
Steep low/mid-level lapse rates coupled with boundary-layer
dewpoints in the 60s are expected to contribute to moderate to
strong instability across the warm sector, supporting vigorous
thunderstorm development by late afternoon into evening as the
mid-level height falls overspread the region. Strengthening vertical
shear with the arrival of the jet streaks will favor supercells
capable of large to very large hail and severe wind gusts. Some
tornado threat could materialize across central ND during the
evening hours as low-level shear strengths in response to an
intensifying low-level jet.
...Day5/Wednesday...
The ensembles depict the elongation of a prominent, western U.S.
trough into the northern Plains, with an associated jet extension
stretching into the upper MS Valley. That notion is confirmed by the
majority of deterministic models, which indicate a significant
short-wave trough and associated mid/upper-level jets moving through
the northern and central Plains. At the surface, there is good
agreement between the deterministic models and ensemble member
clustering that the primary surface low initially over central SD
Wednesday morning will develop north-northeast through the ND-MN Red
River Valley into southeast Manitoba, while a trailing cold front
advances through the eastern Dakotas into the upper MS Valley, mid
MO Valley, and central High Plains.
Steep lapse rates and a very moist boundary layer will contribute to
moderate to strong instability across the warm sector by mid
afternoon, with initial thunderstorm development anticipated along
the front from the eastern Dakotas into western MN. Subsequent storm
initiation appears likely southwestward along the front through the
mid MO Valley into the central Plains. While there is some model
signal that the deep-layer shear vectors may only cross the surface
frontal zone at a small angle, sufficient bulk shear magnitudes will
exist to support supercells and bowing structures amidst potentially
more complex/messy storm modes. All severe-weather hazards are
possible, with that threat quickly spreading through the upper MS
Valley into the upper Midwest Wednesday evening into night.
Should subsequent model runs remain consistent with current trends,
a 30% unconditional probability contour may be included in the next
forecast update.
...Day 6/Thursday...
Both the ensemble mean and deterministic models indicate the
development of a prominent mid-level low over Manitoba or northwest
Ontario, with a belt of unseasonably strong mid-level flow
stretching from the northern or central Plains into the Great Lakes.
At the surface, ensemble member clustering and the deterministic
models indicate the primary low pressure over northwest Ontario with
a trailing cold front stretching from the upper Midwest through the
mid MS Valley into southern Plains.
While mid-level lapse rates are forecast to be weaker than in
previous days, the presence of a moist air mass will contribute to
moderate instability by afternoon within the warm sector. Strong to
potentially severe storms appear possible from the upper Midwest
into Great Lakes southwest into the OH and mid MS Valleys during the
afternoon and evening hours. The models suggest that the strongest
deep-layer shear may lag the surface warm sector to the immediate
west, which casts some uncertainty on the extent of the
severe-weather threat. As such, no area will be delineated in this
forecast.
...Days 7-8/Friday and Saturday...
The ensemble mean solutions suggest a gradual deamplification of the north-central CONUS trough, with a belt of stronger mid-level flow
stretching from the northern Plains through the Great Lakes. At the
surface, there is considerable variability in the position of any
relevant frontal systems that might focus strong to severe storm
development.
..Mead.. 06/06/2026
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