ACUS02 KWNS 220559
SWODY2
SPC AC 220557

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1257 AM CDT Sat Aug 22 2026

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
EASTERN GREAT LAKES INTO THE NORTHEAST...THE NORTHERN PLAINS...AND MONTANA....

...SUMMARY...
Strong thunderstorm activity posing at least some risk for severe
hail and wind appears possible across parts of the northern Rockies
and Great Plains, and across parts of the eastern Great Lakes to the
Northeast, Sunday through Sunday night.

...Montana...
A deamplifying mid-level shortwave trough will move from the Pacific
Northwest into eastern British Columbia on Sunday. As this occurs, a
lee cyclone across Montana will advect moisture northwestward into
central Montana with some 60F dewpoints expected. Moderate mid-level
flow along the southern periphery of this mid-level trough will
overspread a weak to moderately unstable airmass across Montana. The
majority of the forcing will be farther north across Canada,
however, weak height falls and terrain driven circulations should be
sufficient enough for storm development by mid-afternoon across
central Montana. 30 to 35 knots of shear should be sufficient for
storm organization including some supercell potential. In addition,
strong heating will result in steep lapse rates and an environment
supporting damaging winds. 

...Dakotas...
Moderate to potentially strong instability is forecast across
central South Dakota and vicinity on Sunday afternoon, southwest of
a frontal zone. Persistent southwesterly 1km flow is expected for
much of the day. Isentropic ascent within this zone will support the
potential for thunderstorms for much of the day. Thunderstorm
coverage/intensity may increase as a mid-level shortwave trough
approaches the region during the afternoon. In addition, the
low-level jet is expected to strengthen during the evening which
will result in more widespread storm development. The environment,
featuring moderate to strong instability and 35-45 kts of effective
shear, within a zone of moderate forcing, may result in some strong
storms capable of large hail and severe wind gusts. 

...Eastern Great Lakes into the Northeast...
A strong mid-level trough across the Great Lakes will become a
closed upper low across southern Ontario on Sunday. An individual
mid-level trough revolving around the primary trough will become
negatively tilted as it pivots through the Northeast. A secondary
mid-level shortwave trough will dig into the western portion of this
trough and emerge around the base of the trough late Sunday evening.
These features amid the deepening upper low will result in
persistent ascent across the region where weak instability will also
be present. Shear may be relatively weak (20 to 25 knots), which may
limit overall storm organization. However, the cool temperatures
aloft should be sufficient for isolated large hail and damaging wind gusts.

...Arkansas and Vicinity...
Most guidance shows a moderate low-level jet and isentropic ascent
across eastern Oklahoma and into Arkansas late Sunday night and
early Monday. Forecast soundings, other than the HiRes NAM, show
relatively meager instability. Therefore, while thunderstorms are
likely along this zone given the strong forcing, severe storms may
struggle amid relatively weak instability. Therefore, no
probabilities have been added at this time.

..Bentley.. 08/22/2026

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