Mesoscale Discussion 1310
   NWS Storm Prediction Center Norman OK
   0948 AM CDT Wed Jul 22 2020

   Areas affected...eastern WV...southern PA...northern VA...MD...DE
   and far southern NJ

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 221448Z - 221645Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Clusters of thunderstorms will produce damaging winds
   across portions of southern PA and eastern WV, eastward across the
   Chesapeake Bay vicinity through the afternoon and early evening
   hours.

   DISCUSSION...Isolated to scattered thunderstorms from southwest PA
   into northern WV are starting to increase in intensity late this
   morning. 14z Mesoanalysis and modified RAP forecast soundings
   indicate that the area is still experiencing MLCIN, but this is
   expected to quickly erode over the next couple of hours as mostly
   clear skies downstream of this developing activity will result in
   strong heating. In fact, temperatures across southeast PA/southern
   NJ southward into the Piedmont and Chesapeake Bay vicinity are
   already in the low to mid 80s. Surface dewpoints across the region
   are mostly in the low to mid 70s F, and this will aid in MLCAPE
   values as high as 1500 J/kg by early afternoon. Effective shear
   across the region will remain somewhat modest, around 20-30 kt, with
   some localized enhancement from MCVs migrating eastward from the
   Ohio Valley into the MCD discussion area. This will result in
   loosely organized clusters of thunderstorms tracking eastward
   through the afternoon. 

   Aforementioned strong surface heating will allow for the development
   of steep low level lapse rates, and some mixing of the boundary
   layer. As such, this will enhance strong downburst potential, and
   clusters of damaging wind are likely. Some guidance suggests a
   bowing segment or two could develop out of these thunderstorm
   clusters through outflow/storm-scale interactions/mergers or
   smaller-scale cold pool development. If this occurs, any
   forward-propagating bowing segment could increase the damaging wind
   threat locally. 

   Midlevel lapse rates and directional shear will remain modest, but a
   few of the more intense and discrete cells could produce a couple of
   instances of severe hail. Overall, damaging wind is expected to be
   the main concern into this evening. A severe thunderstorm watch will
   likely be needed for portions of the MCD area within the next couple
   of hours.

   ..Leitman/Hart.. 07/22/2020

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

   ATTN...WFO...PHI...AKQ...CTP...LWX...RNK...PBZ...RLX...

   LAT...LON   39108039 39808007 40337955 40567896 40647824 40587666
               40437593 40017523 39497491 38937473 38377480 37767512
               37377550 37157603 37187716 37257829 37467928 37787997
               38198045 39108039