Mesoscale Discussion 1300
   NWS Storm Prediction Center Norman OK
   0101 PM CDT Tue Jul 21 2020

   Areas affected...portions of southern PA...northern/western
   MD...northern VA and the WV Panhandle

   Concerning...Severe potential...Watch unlikely 

   Valid 211801Z - 211900Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Sporadic strong, locally damaging downburst winds are
   possible through the afternoon.

   DISCUSSION...Strong thunderstorms are ongoing across the portions of
   west-central PA southward into the WV Panhandle/northern VA
   vicinity. This convection is mainly being driven by strong diurnal
   heating amid low-to-mid 60s F surface dewpoints. While 30-40 kt
   mid/upper level flow exists across the region, effective shear
   remains weak given less than 15 kt of westerly flow below 3 km, and
   little directional shear. Furthermore, storms are likely
   experiencing the best environmental conditions currently, with
   slightly less favorable conditions with eastward extent.

   Nevertheless, a few strong storms could produce locally damaging
   gusts given relatively high PW values and a deeply-mixed boundary
   layer with steep low level lapse rates. Confidence is longevity of
   any organized convection is rather low at this time, and a watch is
   not expected, though trends will continue to be monitored.

   ..Leitman/Hart.. 07/21/2020

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

   ATTN...WFO...PHI...CTP...LWX...PBZ...

   LAT...LON   40527836 40427653 39927608 39287631 38747656 38627743
               38837889 39397919 40267883 40457864 40527836