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