ACUS02 KWNS 100552
SWODY2
SPC AC 100551

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1251 AM CDT Wed Sep 10 2025

Valid 111200Z - 121200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE NORTHERN AND CENTRAL HIGH PLAINS AND INTERMOUNTAIN WEST...

...SUMMARY...
Isolated strong to severe thunderstorms with hail and severe wind
potential are possible across Montana and the Dakotas. Additional
isolated strong storms may develop over the central High Plains and
Intermountain West.

...Northern and central Plains...
South/southwesterly flow aloft is forecast to increase over the
Northern Rockies/Plains ahead of a shortwave trough along the
eastern periphery of a broader upper low. Weak height falls will
overspread the western fringes of a moistening low-level air mass as
a warm front moves northward with a surface cyclone over central MT.
Low-level upslope is expected much of the day along and north of the
front, which should result in moderate destabilization (MLCAPE
~1500-2500 J/kg). However, some inhibition is also expected given
the glancing influence of the upper ascent and warm mid-level
temperatures. Isolated to widely scattered thunderstorms are
expected late in the afternoon along and north of the warm front
from eastern MT into western ND. Steep mid-level lapse rates and
veering wind profiles could support some supercell structures. It
remain unclear if much of this activity will be surface based given
the best ascent will be north of the front. Still, the degree of
buoyancy and increasing deep-layer shear should support some risk
for hail and severe gusts.

Farther south, isolated storms are possible near a surface trough
from eastern WY into western NE/SD. Forcing for ascent should be
weaker with some residual capping likely limiting development within
the warm sector. High-based storms may form within the drier air
west over the terrain before gradually drifting eastward toward the
richer surface moisture. With limited buoyancy and vertical shear,
organized severe storms are unlikely, but isolated severe gusts are
possible given the steep low-level lapse rates.

...Four Corners and Western Slope...
A belt of stronger mid-level flow southeast of the upper low over
the Great Basin will overspread a modified monsoon air mass in place
over northern AZ/NM into western CO and eastern UT. Afternoon
heating should result in a few hundred J/kg of MLCAPE above
low-level inverted-V thermodynamic profiles. Isolated to widely
scattered storms should develop and move off the higher terrain by
mid morning. Some organization of these storms into clusters or
transient supercells is expected owing to elongated mid-level
hodographs beneath the stronger flow aloft. Given the steep
low/mid-level lapse rates, isolated severe gusts and some small hail
are possible with the stronger storms.

..Lyons.. 09/10/2025

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