SPC MD 1723


MD 1723 Image

Mesoscale Discussion 1723
NWS Storm Prediction Center Norman OK
0136 PM CDT Tue Sep 29 2020

Areas affected...Portions of central/southern VA into NC/SC and
eastern GA

Concerning...Severe potential...Watch unlikely 

Valid 291836Z - 292100Z

Probability of Watch Issuance...20 percent

SUMMARY...Storms capable of producing isolated strong/gusty winds
around 40-60 mph should continue through the afternoon. Watch
issuance is unlikely.

DISCUSSION...Thunderstorms are gradually strengthening this
afternoon across parts of the western/central Carolinas along and
just ahead of a surface cold front. Other isolated storms are
ongoing across parts of coastal NC/SC. As a large-scale upper trough
continues pivoting eastward across the OH/TN Valleys and Southeast,
a weak surface low currently over western NC should develop
northeastward into VA. The cold front trailing from this surface low
will focus storm development through the remainder of the afternoon,
with one or more broken lines of storms expected along its length
from central VA to SC and eastern GA. 12Z observed soundings from
RNK, GSO, MHX, and CHS all showed the presence of poor low and
mid-level lapse rates. This should generally temper updraft
strength, even as modest diurnal heating of a moist low-level
airmass occurs. Still, around 500-1250 J/kg of MLCAPE has already
developed ahead of the front per latest mesoanalysis estimates, with
the slightly better instability farther south across eastern GA and

Various VWPs across this area show strong mid/upper level
south-southwesterly winds that are nearly unidirectional. Around
40-50 kt of effective bulk shear should foster some storm
organization, with a mix of line segments and perhaps low-topped
supercells possible. Isolated strong/gusty winds, generally in the
40-60 mph range, may occur with any of these storms as they move
slowly east-northeastward in tandem with the advancing cold front.
With the poor lapse rates, weak instability, and strong flow aloft
generally parallel to the surface front, the overall severe threat
should remain isolated/marginal. Accordingly, watch issuance appears
unlikely at this time.

..Gleason/Grams.. 09/29/2020

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   36567751 36347680 36077640 35537629 34807690 34517729
            34247771 33797796 33857848 33587891 33167911 32907948
            32078080 31128133 30758142 30968255 31338288 32098243
            32748209 33338185 34098153 34708139 35518117 36688062
            38237861 38177782 36567751 

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