ACUS01 KWNS 121244
SWODY1
SPC AC 121243

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0743 AM CDT Fri Sep 12 2025

Valid 121300Z - 131200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
MONTANA EAST ACROSS MUCH OF THE DAKOTAS...AND IN THE FOUR CORNERS REGION...

...SUMMARY...
A few storms capable of isolated severe wind gusts and hail are
possible across the Four Corners region, and from eastern Montana
into the Dakotas.

...Synopsis...
An upper trough will remain over the Intermountain West, making slow
eastward progress through tonight. An embedded disturbance is
forecast to move from CO into the Dakotas late in the day, while a
midlevel jet rounds the base of the trough across AZ overnight.
Gradual height falls will occur across the length of High Plains
primarily overnight as the upper-level ridge to the east gradually
weakens.

...Eastern MT into the Dakotas...
Thunderstorm development/intensification is expected across MT/WY
east of a mid-level trough axis, where cool mid-level temperatures
and surface dew points in the 50s will lead to MLCAPE in the 500 -
locally 1000 J/kg range. Southwesterly deep-layer shear averaging
20-35 kts will be favorable for isolated storms with hail potential.
As storms move/develop farther east across eastern MT/western
ND/northwest SD towards evening, greater instability (MLCAPE on the
order of 2000 J/kg) should result in a severe hail and wind risk
with isolated stronger storms within a similarly-sheared
environment. Although the low-level jet should be weaker in this
area tonight, lingering instability across the western Dakotas
suggests some continued severe risk, primarily for strong/damaging
gusts, into the overnight hours.

...Four Corners Region...
Scattered to numerous thunderstorms are expected to
develop/intensify today from eastern AZ/southeast UT across western
portions of NM/CO, within a moist plume on the eastern periphery of
the mid-level trough. Cool mid-level temperatures will contribute to
modest MLCAPE, with locally higher values (above 1000 J/kg) over
southeastern AZ. A predominantly cellular or cluster mode is
expected, with isolated stronger storms capable of marginally severe
wind and hail. Storms should persist into the evening over western
NM/CO, with a few stronger storms remaining possible.

..Bunting/Broyles.. 09/12/2025

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