512
ACUS03 KWNS 080730
SWODY3
SPC AC 080729

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Mon Sep 08 2025

Valid 101200Z - 111200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Scattered showers and thunderstorms are possible over parts of the
Northwest, Northern Rockies and High Plains Wednesday. A stronger
storm or two is possible, but severe potential is low.

...Synopsis...
The broad upper low over the western US is forecast to deepen slowly
as shortwave ridging to the east also intensifies. Between the
trough and the ridge, a 50+ kt mid-level jet streak and vort max are
forecast to lift northward across the Great Basin into the northern
Rockies. Ascent from the approaching jet will overspread a weak lee
trough, eventually resulting in surface cyclogenesis over portions
of central and western MT. The deepening low will draw modest
moisture westward across parts of MT, WY and the western Dakotas,
potentially supporting isolated thunderstorms, while scattered
storms are more likely over parts of the Great Basin and northern
Rockies.

...Northern and central High Plains...
As the lee low deepens over central MT, low-level moisture will
begin to move west along the trailing surface trough. Robust heating
is expected over much of the High Plains owing to clear skies
beneath the pronounced mid-level ridging. Weak ascent from the
approaching vort max/jet should aid in gradual destabilization
through the afternoon, though some capping is likely to be in place
along the narrow warm/moist sector. This should limit diurnal
thunderstorm development across much of the High Plains. Still, some
potential for isolated storm development exists across the Black
Hills or along the lee trough into eastern WY. Sporadic severe gusts
would be the main hazard should sustained deep convection develop
given steep low and mid-level lapse rates. Confidence in storm
development remains too low for severe probabilities at this time
given the limited synoptic ascent.

...Northwest and northern Rockies...
Closer to the center of the upper low across eastern WA/OR, northern
ID and western MT, scattered thunderstorms are likely Wednesday as
ascent from the approaching mid-level jet intensifies. Cooler
mid-level temperatures will overspread modest low-level moisture
(40s F dewpoints) supporting weak destabilization through the day.
Some gusty thunderstorm winds are possible owing to fairly steep
low-level lapse rates, and scattered storm coverage. However,
largely meridional flow aloft, remnant cloud cover, and MLCAPE
generally less than 500 J/kg suggest organized severe potential
should remain quite limited.

..Lyons.. 09/08/2025

$$