SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0323 PM CDT Mon Sep 12 2022
Valid 122000Z - 131200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
MID ATLANTIC AND CENTRAL ARIZONA...
CORRECTED FOR THUNDER LINE
...SUMMARY...
Isolated strong to severe thunderstorms may occur across parts of
the Mid-Atlantic and Northeast, and over portions of Arizona.
...20z Update...
The Marginal Risk across portions of the Mid Atlantic has been
shifted east to better align with a lee trough along the eastern
foothills of the Appalachians and Blue Ridge Mountains. Ongoing
strong storms will continue to pose a low-end risk for primarily
damaging wind gusts, marginally severe hail, and perhaps a brief
tornado within the modestly unstable and sheared environment.
Additional storm development is possible this evening and overnight
as the surface cold front begins to surge eastward into DelMarVA and
southern New England.
The Marginal risk across the Southwest remains unchanged. A few
high-based storms capable of damaging outflow winds will remain
possible into this evening. Please see the prior outlook for
additional details and information.
..Lyons/Hart.. 09/12/2022
.PREV DISCUSSION... /ISSUED 1118 AM CDT Mon Sep 12 2022/
...Synopsis...
A surface cold front, recently analyzed from the upper OH River
Valley into the lower MS River Valley, will continue to push east
into the Northeast, Mid-Atlantic, and Southeast Coast over the next
24 hours. Aloft, an upper trough has begun to slowly migrate east,
which will resulting in modest surface pressure falls along/ahead of
the front across the Mid-Atlantic region this evening. The eastward
progression of the wave and the slight deepening of the low will
result in increasing shear that may support organized convection as
thunderstorms develop along and just ahead of the front. Across the
Southwest, an upper low will continue to meander off the coast of
southern California. A persistent influx of unseasonably high
moisture into AZ will support thunderstorm development off the
terrain of southern/southeast AZ.
...Mid-Atlantic...
Early morning fog/low stratus is quickly mixing out across VA/MD,
allowing temperatures to warm into the upper 70s and low 80s from
the Carolinas into north-central MD. These temperatures are warmer
than expected by most guidance by 16 UTC, suggesting that
surface-based instability and low-level lapse rates may be
higher/steeper than indicated by morning model runs. Despite the
clearing skies, poor low and mid-level lapse rates sampled by 12 UTC
soundings will likely limit overall buoyancy values to near 1000
J/kg MLCAPE this afternoon. Combined with increasing deep-layer
shear, a few strong to severe storms are expected along the front.
Semi-organized clusters and/or linear segments will pose a damaging
wind threat, and any discrete cells may acquire sufficient
organization to pose a hail and brief/weak tornado threat.
...Arizona...
Thunderstorm development off the Mogollon Rim and the
Chiricahua/Pinaleno mountains is expected by late afternoon amid a
persistent influx of unseasonably high low-level moisture (dewpoint
values in the upper 60s are near the 90th percentile for
mid-September). Despite modest flow aloft, ample daytime heating
will promote steep low-level lapse rates/deep boundary-layer mixing
favorable for a few strong to severe gusts as convection propagates
off the terrain.
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