Mesoscale Discussion 1136
   NWS Storm Prediction Center Norman OK
   0341 PM CDT Wed Jun 30 2021

   Areas affected...Southern Pennsylvania and the West
   Virginia...Maryland...Virginia border

   Concerning...Severe Thunderstorm Watch 328...

   Valid 302041Z - 302245Z

   The severe weather threat for Severe Thunderstorm Watch 328
   continues.

   SUMMARY...An isolated severe wind threat will continue into the
   early evening hours across parts of WW 328, as well as across
   southern/southeast Pennsylvania and the broader northeast WV,
   northern VA, and western MD region. A downstream watch will be
   issued to address this potential.

   DISCUSSION...Recent regional radar and IR imagery shows convection
   gradually decreasing across southwest PA as a cold pool becomes
   established (as noted in recent surface observations). Convective
   development across PA has largely become confined to outflow
   boundaries on the periphery of this air mass where the thermodynamic
   conditions remain favorable for a supporting strong to severe
   storms. The severe threat will be greatest on the southern and
   eastern edges of the cold pool where temperatures in the mid/upper
   90s are maintaining steep low-level lapse rates that will support
   damaging winds with any stronger downbursts. 

   Storms developing off the terrain near the WV/MD/VA border should
   move into southern to southeastern PA over the next few hours and
   may produce a few instances of damaging winds. The extent of the
   threat may largely be determined by convective coverage, which
   appears localized at this point. However, one or two organized
   clusters could evolve in this environment and pose a more
   substantial threat. Despite the conditional nature of the threat, a
   watch will be issued to address this potential.

   ..Moore.. 06/30/2021

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

   ATTN...WFO...PHI...BGM...CTP...LWX...PBZ...RLX...

   LAT...LON   39728018 40127916 40657800 41117714 41127623 40777573
               40377554 39897601 39437653 39087716 39097788 39077864
               39187924 39337990 39728018