ACUS01 KWNS 111712
SWODY1
SPC AC 111710

Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1210 PM CDT Thu Sep 11 2025

Valid 111630Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
MONTANA INTO WESTERN NORTH DAKOTA...

CORRECTED FOR PROB GRAPHICS

...SUMMARY...
Scattered severe thunderstorms are expected over eastern Montana
into western North Dakota late this afternoon through the evening.
The primary hazards are severe wind gusts and large hail.

...Synopsis...
Water-vapor imagery shows a large cyclone over the West with a
downstream ridge over the Great Plains, and a trough centered over
the Lower Great Lakes. Southwesterly mid to high-level flow extends
from the base of the larger-scale western U.S. trough northeastward
through the Great Basin and into the northern Great Plains. A
mid-level disturbance implied in water-vapor imagery over western
WY, is forecast to move northeast into eastern MT/western ND towards
this evening.

In the low levels, a plume of seasonably rich moisture will protrude
northward from the central Plains into the Dakotas and eastern MT.
A lee trough will extend southward from a surface low over the
northern High Plains.

...Rockies into the northern Plains...
An ongoing cluster of thunderstorms associated with warm-air
advection near the ND/Manitoba border will continue to move
east-northeastward into southern Canada ahead of a pair of MCVs over
western ND/eastern MT. Diurnal heating over the higher terrain from
near the Four Corners northward into southern MT will favor
scattered thunderstorms developing during the midday into the early
afternoon. Storm coverage will increase further over the central
Rockies during the afternoon, with the stronger storms capable of an
isolated hail/wind threat. As the airmass destabilizes over the
plains, particularly across eastern MT within the moist plume
primarily north of the surface low, isolated to scattered storms are
forecast by mid to late afternoon. This initial activity will
probably develop near the MT/WY border with upscale growth into a
cluster possible during the evening. Deep-layer shear supporting
organized storm modes coupled with steep lapse rates, will combine
to aid in several stronger storms capable of a hail/wind threat.
The wind threat will probably continue into ND during the evening
within the terminus region of a 35-40 kt southerly LLJ. A gradual
transition to increasingly elevated convection is expected late as
convective inhibition increases and the overall severe risk lessens.

..15_ows.. 09/11/2025

$$

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