SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Thu Sep 08 2022
Valid 082000Z - 091200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER MIDWEST...WYOMING/BLACK HILLS...FLORIDA PENINSULA...AND
THE MIDDLE TEXAS COAST...
...SUMMARY...
Isolated severe hail and locally damaging winds may occur this
evening into the overnight across parts of the Upper Midwest.
Isolated severe wind gusts remain possible across parts of Florida,
the middle Texas Coast, and Wyoming to the Black Hills vicinity
through the rest of the afternoon and into the early evening.
...20Z Update...
Aside from trimming low wind probabilities behind ongoing convection
across the FL Peninsula, no appreciable changes have been made to
the ongoing forecast. See Mesoscale Discussion 1769 for more details
on the near-term threat for strong to locally severe thunderstorm
wind gusts across parts of WY and vicinity.
..Gleason.. 09/08/2022
.PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Sep 08 2022/
...Upper Midwest...
No changes warranted for this region. Low/mid-level warm advection
is expected from a stout upstream EML regime, emanating from where
record high temperatures have been set in prior days over a large
portion of the interior West. This, in combination with a
return-flow process that lacks robust connection to the western Gulf
and therefore limits rich boundary-layer moisture, should keep an
impinging cold front capped from thunderstorm development through
late afternoon.
By evening, mid-level height falls should overspread the front in
advance of a broad upper trough reaching the Prairie Provinces to
northern Great Plains. Strengthening low-level convergence and
low-level arm/moist advection may provide sufficient ascent to
weaken the EML and yield isolated thunderstorms initially from
west-central to northeast Minnesota. Some guidance suggest this
process will be more pronounced overnight and thus displaced
southward. Regardless, convection is most likely to be rooted on and
to the cool side of the southeast-progressing cold front. Deep-layer
winds will largely be stronger deeper into the stable air mass away
from the immediate front, but still adequate to support rotating
updrafts amid moderate elevated buoyancy. Isolated large hail is the
primary threat, but locally damaging winds from strong gusts are
possible.
...Wyoming/Black Hills vicinity...
The trailing portion of a cold front will move south from eastern
Montana into northern Wyoming this afternoon. As this occurs,
isolated to scattered thunderstorms should develop over the higher
terrain of far southern Montana and northwest/north-central Wyoming
and then spread east-southeast. Moisture will be poor with surface
dewpoints generally in the 30s F, but steep low/mid-level lapse
rates should support meager MLCAPE to around 300 J/kg. High-based,
skeletal convection may produce isolated severe gusts, augmented by
momentum transport from strengthening mid-level winds, and small
hail. This threat should diminish rapidly near sunset.
...Central/south Florida Peninsula...
To the east of a low centered over the northern Gulf of Mexico,
scattered, semi-organized, slow-moving thunderstorms will move
across the Florida Peninsula through late afternoon and evening.
While low/mid-level winds are not overly strong, ample veering and
as much as 20-25 kt effective shear may support a couple of
weak/transient supercells, and more prevalently, semi-organized
linear segments otherwise. A localized severe storm or two could
occur mainly through the afternoon.
...Middle Texas coast/South-Central Texas...
In a somewhat similar regime to yesterday across east Texas,
modestly enhanced northerly winds aloft in conjunction with moderate
buoyancy could yield a few stronger storms this afternoon, with
localized wind damage the most probable hazard.
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