SPC AC 111603
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1103 AM CDT Sun Sep 11 2022
Valid 111630Z - 121200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
Severe-thunderstorm potential appears minimal today and tonight.
Mid-morning surface observations and satellite imagery clearly show
the east/southeastward progression of a cold front into the MS River
Valley. Modest cold advection following this front will continue to
drive weak height falls aloft over the central CONUS over the next
24 hours, leading to a gradual deepening of the upper wave over the
Midwest. Surface analyses also show the front surging relatively
faster across the lower MS River Valley/eastern southern Plains
compared to locations closer to the surface low over southern Lake
Michigan. This suggests that the occlusion process has likely begun
and will continue through the day. Despite this, the amplification
of the upper air regime will support gradual deepening of the nearly
stationary surface low over northeast IL through tonight.
Thunderstorms have already begun to develop along the cold front,
and will expand in coverage through the afternoon hours as the front
pushes east through the OH Valley region. Across the northern Gulf
coast, a decaying cut-off low will migrate east/northeast through
the day. Ample moisture advection associated with this feature
combined with weak/broad ascent and areas of daytime
heating/surface-based destabilization will support another day of
scattered thunderstorms from FL northward to the Mid-Atlantic coast.
Unseasonably high moisture associated with the remnants of Tropical
Storm Kay will continue to foster thunderstorm chances across a
broad area of the Southwest today. Stronger wind gusts are possible
with any thunderstorm moving into a well-mixed region, but weak flow
aloft will limit the probability of numerous severe gusts.
...Middle OH River Valley..
Morning RAOBs ahead of the cold front across the OH River Valley
show ample boundary-layer moisture, but weak low and mid-level lapse
rates. Extensive cloud cover will likely hinder surface-based
destabilization for much of the day. However, evidence of elevated
instability with limited inhibition is noted in observed and
forecast soundings, as well as latest satellite trends. The
deepening of the upper low will support increasing flow and
elongating hodographs above 3 km through the day, which may provide
adequate effective shear for a few stronger, more organized cells or
clusters. If storms can become rooted within the boundary, a few
strong wind gusts may occur. This will be most likely for areas that
can see surface temperatures warm through the mid/upper 70s, but
confidence in a sufficiently widespread severe risk remains too
limited to introduce probabilities.
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