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Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1247 AM CDT Wed Sep 11 2024

Valid 111200Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL GULF COAST...

...SUMMARY...
A few tornadoes are possible across the central Gulf Coast vicinity
on Wednesday into Wednesday night, in association with Tropical
Cyclone Francine.

...Central Gulf Coast...
Hurricane Francine is forecast to continue northeastward across the
northwest Gulf of Mexico today, likely making landfall over the
central LA Coast during the afternoon. Easterly/northeasterly winds
are expected across much of the Southeast from the morning through
the afternoon, which will likely keep the tropical airmass
associated with this cyclone offshore (or only over immediate
coastal portions of south-central and southeast LA). As the storm
makes landfall, mid 70s dewpoints will spread northward into more of
southeast LA, southern MS, southern AL, and the far western FL
Panhandle during the evening. This increased low-level moisture
could boast buoyancy enough for more sustained/persistent updrafts.
Robust low to mid-level wind fields associated with the cyclone will
support rotation within any more persistent updrafts, with some
isolated low-topped supercells possible. 

Current guidance suggests the highest tornado potential will exist
from 21Z through 04Z from far southeast LA across southern MS/AL.
Mid 70s dewpoints and southerly/southeasterly surface winds will
persist from southern MS/AL into the far western FL Panhandle,
supporting a low-probability tornado risk through early Thursday
morning.

...Parts of the Northwest/Northern Rockies...
The strong shortwave trough currently off the Pacific Northwest
coast is forecast to continue eastward throughout the period, while
also deepening/maturing. By early Thursday morning, this shortwave
trough will likely extend from the ID Chimney/northwest MT into the
Great Basin. Strong mid-level flow will acco*pany this shortwave,
spreading eastward from northern CA through the Great Basin as the
wave progresses eastward. 

Relatively cool mid-level temperatures are already in place from the
northern Intermountain West into the northern Rockies, with 500 mb
temperatures from -11.5 to -14 deg C sampled on the regional 00Z
soundings. Strong heating and boundary-layer mixing beneath these
cool mid-level temperature will result in modest buoyancy during the
afternoon ahead of the shortwave trough. Afternoon thunderstorm
development is anticipated as large-scale ascent increases amid this
destabilized and modest buoyant airmass. The stronger flow and
vertical shear will be displaced south of the region, but moderate
shear co*bined with the cool temperatures aloft could still
contribute to some isolated hail. High cloud bases and resultant
strong outflow could result in some gusty winds as well. 

...Northern High Plains...
Lee surface troughing will deepen throughout the day, with
southeasterly surface winds increasing in response. Strong
heating/mixing is anticipated across the region. Low-level moisture
advection may help offset some of this mixing but dewpoints will
likely still drop into the mid 40s to low 50s across much of the
region. Highest dewpoints are anticipated across northeastern MT and
western North Dakota. Even with this limited moisture, the strong
heating should destabilize the airmass. Late afternoon thunderstorms
are anticipated with this destabilized airmass as both increasing
large-scale ascent and low-level convergence provide the lift needed
for convective initiation. Vertical shear will likely be strong
enough for some updraft organization (particularly across northwest
MT), and high cloud bases will contribute to the potential for
strong outflow capable of damaging gusts.

..Mosier/Lyons.. 09/11/2024