Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1239 AM CDT Fri Aug 22 2025
Valid 221200Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
CENTRAL/NORTHERN HIGH PLAINS AND UPPER MIDWEST AND OVER PARTS OF THE
SOUTHWESTERN UNITED STATES...
...SUMMARY...
Strong to locally severe thunderstorms are possible from parts of
the central and northern High Plains into the Upper Midwest, and
across parts of the southwestern United States.
...Central/Northern High Plains-Upper Midwest...
Central Canadian upper trough is forecast to advance into western
ON/MN by 23/00z as 500mb speed max settles into the base of the
trough over the upper Red River region of eastern ND/MN. High-level
diffluent flow will be noted across much of the Upper Midwest ahead
of this feature which will encourage deep convection along the
frontal zone from the upper Great Lakes into portions of the Mid MO
Valley. Early in the period, remnant MCS activity may be ongoing
across southern MN/southeast SD. However, left-over convective
debris may also inhibit surface heating, but may enhance an
afternoon boundary for potential thunderstorm development. Latest
model guidance suggests the front may be multi faceted with some of
the stronger boundary-layer heating expected behind the initial wind
shift across SD into northern MN - well northwest of high PW air
mass. As a result, forecast soundings suggest surface parcels may
struggle to reach convective temperature along the leading wind
shift, with only modest lapse rates expected. Even so, deep-layer
shear will be more than adequate for sustaining organized updrafts
where frontal convergence aids convective development.
Higher confidence in robust convection is expected across portions
of CO into southeast WY. Strong surface heating should aid
thunderstorm development across the higher terrain, along the
northern periphery of the Four Corners upper high. This activity
should propagate southeast toward lower elevations where it will
encounter favorably moist, but weak upslope flow. Hail and wind are
possible with this activity.
...Arizona...
Upper high is forecast to shift slowly west across southern UT
during the day1 period. This will ensure modest easterly 500mb flow
across the southern half of AZ. Strong boundary-layer heating will
once again prove instrumental in convective development over the
higher terrain. This activity will spread toward the lower deserts
during the evening with an attendant risk for at least locally
severe wind gusts.
..Darrow/Weinman.. 08/22/2025
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