[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 171748
SWOMCD
SPC MCD 171747
VAZ000-MDZ000-NCZ000-WVZ000-TNZ000-SCZ000-KYZ000-GAZ000-171945-

Mesoscale Discussion 1248
NWS Storm Prediction Center Norman OK
1247 PM CDT Fri Jul 17 2020

Areas affected...portions of the Mid Atlantic into the southern Ohio
River Valley region.

Concerning...Severe potential...Watch unlikely

Valid 171747Z - 171945Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated downburst winds are possible this afternoon as
thunderstorms continue to develop, and may result in occasional
damaging winds. A watch is not likely due to the isolated nature of
the threat.

DISCUSSION...Regional radar and visible satellite imagery show
convective initiation already underway across the southern Ohio
River Valley, and initiation imminent across portions of NC and VA.
These storms are largely forming with a weak confluence zone
associated with a stationary boundary, aided by areas of orographic
ascent along the higher terrain and low-level parcels reaching their
convective temperatures. Boundary-layer deepening/mixing is also
ongoing based on falling dewpoint values and steepening low-level
lapse rates (per RAP mesoanalysis, which shows a region of 7-8 C/km
0-3 km lapse rates along and south of the stationary boundary).
Further boundary-layer destabilization and an increase in
thunderstorm coverage are expected heading into the afternoon hours
as daytime heating continues. Although 2000-2500 J/km MLCAPE is
already in place over the region, weak deep-layer flow will favor
clustered storm modes and mainly a downdraft-driven damaging wind
potential - especially over areas where boundary-layer mixing is the
deepest. Due to the isolated nature of this threat, a watch is not
likely.

..Moore/Hart.. 07/17/2020

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

ATTN...WFO...AKQ...LWX...RAH...RNK...RLX...GSP...MRX...JKL...
LMK...OHX...

LAT...LON   37578423 37698339 37698046 38487842 38587666 38097611
            37717616 36117790 35837930 35428101 34908309 35398416
            36218489 37088518 37578423
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