Storm Prediction Center Mesoscale Discussion 805

   Mesoscale Discussion 0805
   NWS Storm Prediction Center Norman OK
   0209 PM CDT Wed May 20 2026

   Areas affected...portions of the Mid-Atlantic

   Concerning...Severe Thunderstorm Watch 234...235...

   Valid 201909Z - 202045Z

   The severe weather threat for Severe Thunderstorm Watch 234, 235
   continues.

   SUMMARY...Potential for damaging wind gusts and isolated large hail
   is increasing across portions Severe Thunderstorm Watch 234 and will
   expand into downstream WW 235 through the afternoon.

   DISCUSSION...Convective coverage has increased across portions WW234
   over the past 1-2 hours amid continued destabilization ahead of an
   approaching cold front, with two reports of wind damage noted across
   far southern Pennsylvania. Recent radar trends suggest that some
   upscale growth/clustering of convection is ongoing along various
   outflow boundaries. The environment downstream of this convection
   has continued to destabilize, with latest objective analysis
   depicting 1000-1500+ J/kg MLCAPE across the region. Continued
   insolation is also yielding steepening low-level lapse rates and
   well-mixed boundary layer profiles (evident in recent regional ACARS
   profiles and latest surface observations, respectively), with
   surface dewpoint depressions approaching/exceeding 25-30 F. With
   further convective clustering expected, this is expected to yield
   increasing potential for damaging wind gusts across the eastern
   portions of WW234 through the afternoon, with activity eventually
   forecast to spreading downstream into WW235. Latest high-res
   guidance (including recent WoFS runs) also depicts this increasing
   potential.

   ..Chalmers.. 05/20/2026

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

   ATTN...WFO...PHI...BGM...CTP...LWX...

   LAT...LON   38877702 38597798 38587838 38817865 39307840 40147793
               40667717 40907651 41027579 40957542 40707517 40257520
               39827546 39477586 38877702 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN