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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1243 AM CDT Thu Sep 12 2024

Valid 121200Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN ASSOCIATION
WITH TS FRANCINE AND OVER THE EASTERN MONTANA REGION...

...SUMMARY...
A few tornadoes are possible today, mainly in the morning and
afternoon from the Florida Panhandle to north-central Alabama.
Scattered large hail and severe gusts are expected across the
eastern Montana vicinity during the afternoon to early evening.

...Tropical Storm Francine...

TS Francine continues its slow drift inland, and is expected to
progress across southern/central MS to near Memphis by the end of
the period. Strong low-level shear will spread/develop north, to the
immediate north-east of the center of circulation. As is typical,
poor lapse rates will limit buoyancy today, and latest model
guidance suggests only a narrow corridor of weak-modest 0-3km lapse
rates, primarily across southwestern into west-central AL. Robust,
long-lived supercells have struggled to develop with this system,
and forecast thermodynamic profiles are not particularly impressive.
Even so, scattered lightning is noted with deeper updrafts offshore,
along with a few supercells. This activity will spread inland later
this morning and there remains some concern for a few tornadoes
where boundary-layer destabilization is maximized.

...Eastern Montana Region...

Strong upper trough has progressed into the northern Intermountain
region, from western ID into NV. This trough will advance into the
northern Rockies later today as a 500mb speed max translates across
UT into eastern WY/MT. This evolution will warrant a cold front
surging into eastern MT/northwest WY by 18z. Greatest boundary-layer
heating will initially be across eastern WY, but significant surface
heating across eastern MT should lead to steep 0-3km lapse rates and
convective temperatures will likely be breached across northern
WY/southern MT by 20z. Deep convection should readily develop over
the Big Horn Mountains/surrounding higher terrain as the left-exit
region of the 500mb speed max approaches. Latest hr** guidance
strongly favors robust convection evolving by mid afternoon, with
several long-lived supercells depicted in most members. Forecast
soundings favor sustained rotating updrafts and high-based
convection should generate strong winds, and perhaps large hail.
While PWs are seasonally low, ample buoyancy will likely exist for
allowing this activity to spread into western ND later in the
evening, especially given the strengthening LLJ across this portion
of the Dakotas after sunset.

..Darrow/Lyons.. 09/12/2024