SPC Aug 29, 2020 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0228 AM CDT Sat Aug 29 2020

Valid 311200Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
SOUTHERN PLAINS INTO THE ARKANSAS AND LOWER MISSISSIPPI VALLEYS...

...SUMMARY...
Thunderstorms associated with large hail and wind damage will be
possible across parts of the southern Plains on Monday. Wind damage
will also be possible in parts of the Arkansas and lower Mississippi
Valleys.

...Southern Plains/Arkansas and Lower Mississippi Valleys...
Mid-level flow will become southwesterly across the southern Plains
on Monday as an upper-level trough moves through the Intermountain
West. At the surface, a cold front will advance quickly
southeastward into the Texas Panhandle, western Oklahoma and
southern Kansas on Monday, and then stall. Surface dewpoints in the
upper 60s to lower 70s F to the southeast of the front, will result
in moderate instability by afternoon. Thunderstorms are expected to
develop along the front around midday with convective coverage
increasing through the afternoon. In addition to the moderate
instability, NAM forecast soundings in Oklahoma show 0-6 km shear of
40 to 50 kt. This would support supercell development early in the
event when cell coverage will be less, allowing for storms to be
more discrete. Wind damage will also be possible with supercells.
The wind-damage and hail threat is expected to continue through the
evening as MCS development takes place across the southern Plains.
There is some model spread among the solutions which introduces
uncertainty. Differences exist in the timing of the front and amount
of instability. At this time, it appears that the potential for a
severe threat will be greatest in parts of the southern Plains.

Further to the east into the Arkansas and lower Mississippi River
Valleys, moderate instability is forecast to be in place by
afternoon. Thunderstorms will be possible along an east-to-west
gradient of instability from eastern Oklahoma into northern
Mississippi. Model forecasts show 0-6 km shear of 30 to 35 kt with
steep low-level lapse rates. This environment would support a
wind-damage threat during the mid to late afternoon. As the southern
Plains MCS moves into the region from the west during the late
evening and overnight period, isolated damaging wind gusts will also
be possible.

...Mid-Atlantic...
A shortwave trough is forecast to move across the southern
Appalachians on Monday. At the surface, a moist airmass will be in
place from the Carolinas northward into the Mid-Atlantic. As
moderate instability develops during the afternoon, thunderstorm
development will be likely as large-scale ascent moves into the
region ahead of the shortwave trough. Forecast soundings across the
Mid-Atlantic Monday afternoon show 0-6 km shear of 30 to 35 kt along
with steep low-level lapse rates. This should be favorable for
marginally severe wind gusts with the stronger multicells.

..Broyles.. 08/29/2020

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from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day3otlk_0730.html