ACUS01 KWNS 121641
SWODY1
SPC AC 121639

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1139 AM CDT Fri Sep 12 2025

Valid 121630Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE FOUR
CORNERS AREA AND NORTHERN HIGH PLAINS...

...SUMMARY...
Isolated severe storms will be possible today across the Four
Corners area and central Rockies, with an increasing risk for severe
storms into late afternoon and tonight across the northern Plains.

...Four Corners Region/central Rockies...
Ahead of the prominent upper trough centered over the Great Basin
and Lower Colorado River Valley, a lead mid-level impulse and
related height falls and a strengthening of cyclonic flow aloft will
influence the region. Cooling mid-level temperatures and a modestly
warming boundary layer will further steepen lapse rates diurnally,
with strong to severe storms expected to further develop into the
afternoon. Relatively strong flow aloft with 40+ kt effective shear
will support some supercell structures, with a related enhanced
potential for severe hail, aside from locally gusty thunderstorm
winds. More severe-favorable ingredients and a somewhat higher
potential for severe storms appears to exist across the Four Corners
vicinity including northwest New Mexico across western Colorado
through the afternoon.

...Northern Plains including Eastern Montana/western Dakotas...
Thunderstorm development/intensification is expected by late
afternoon, initially on an isolated basis across central/eastern
portions of Montana and Wyoming. Cooling mid-level temperatures and
surface dew points in the 50s F will contribute to 500-1000 J/kg
MLCAPE. Southwesterly deep-layer shear averaging 20-35 kt will be
favorable for isolated storms with hail potential. Storm coverage
should steadily increase into the evening toward the western
Dakotas, aided by the arriving influence of greater forcing for
ascent as located over the central Rockies early today. Hail
potential will become more common this evening, with localized
severe wind potential also modestly increasing. Strong/locally
severe storms will potentially persist overnight across the western
and central Dakotas.

...Northern/central Minnesota to northwest Wisconsin...
Very isolated elevated severe storms, with hail as the most probable
hazard, may continue east-southeastward today, semi-focused by
elevated moisture transport well to the north of a warm front.

..Guyer/Jirak.. 09/12/2025

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