979
ACUS01 KWNS 220056
SWODY1
SPC AC 220055

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0755 PM CDT Thu Aug 21 2025

Valid 220100Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN PLAINS...

...SUMMARY...
Scattered severe thunderstorms remain possible across portions of
the northern Plains and Upper Midwest tonight, with severe wind
gusts and large hail the primary concerns. A few strong to severe
storms may also occur across parts of southern Arizona this evening.

...01z Update...

Upper ridge has flattened considerably across the northern Plains in
response to SK short-wave trough. Mid-level flow will gradually veer
across the Dakotas as a strong 500mb speed max translates through
the base of the trough along the international border late tonight.
As this occurs, surface front currently draped from northwest
MN-central SD will gradually sag southeast. Thunderstorm coverage
along the boundary remains isolated, and this may continue much of
the evening until a secondary short wave approaches later tonight.
While a meaningful LLJ is not expected ahead of this feature, latest
model guidance continues to suggest a weak disturbance will eject
across northeast WY/Black Hills region. Elevated convection could
markedly increase after 06z across much of SD along/north of the
front. Earlier thoughts regarding severe continue, but have lowered
severe probabilities across northern MN to reflect less storm
coverage along this portion of the boundary.

AZ: Upper ridge is holding across the Four Corners region and
favorable easterly flow is guiding terrain-induced convection toward
the lower deserts. Scattered robust convection is expected to spread
toward the more populated ares of the PHX metro over the next few
hours. Gusty winds are the primary concern.

..Darrow.. 08/22/2025

$$