Mesoscale Discussion 0814
   NWS Storm Prediction Center Norman OK
   0102 PM CDT Thu Jun 04 2020

   Areas affected...Central VA...Central MD...South-Central PA

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

   Valid 041802Z - 042000Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Increasing thunderstorm coverage with an attendant threat
   for damaging wind gusts is expected.

   DISCUSSION...Visible satellite imagery shows increasing cumulus from
   central VA northward into south-central PA. Thus far, the better
   vertical development has occurred over the higher terrain with the
   cumulus downstream has remained rather flat. With temperatures now
   in the upper 80s/low 90s and dewpoints still in the upper 50s to low
   60s, the air mass across the region has destabilized with recent
   mesoanalysis indicating little to no convective inhibition remains.
   Mid-level lapse rates over the region are rather weak, but the warm
   and modestly moist low-level conditions still support MLCAPE from
   500 to 1000 J/kg. MLCAPE will likely remain near these values even
   as the temperatures warm a few more degrees due to mixing of the
   boundary-layer moisture. 500-mb flow increases from about 25 kt over
   south-central VA to 40 kt over central PA. Vertical shear follows
   this pattern, with around 30 kt of 0-6 km bulk shear across PA.

   Expectation is for thunderstorm coverage to increase from central VA
   into central PA as storm move off the higher terrain into northern
   Piedmont. Given the relatively modest vertical shear, only loosely
   organized mulitcells are anticipated. However, the well-mixed
   boundary layer and resulting steep low-level lapse rates beneath
   relatively moist mid-level will contribute to an environment very
   supportive of strong downbursts. Given the expected storm coverage,
   a watch will likely be needed for portions of the area within the
   next hour or two.

   ..Mosier/Grams.. 06/04/2020

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

   ATTN...WFO...AKQ...CTP...LWX...RNK...

   LAT...LON   39327864 39897833 40467783 40597700 40007641 37867709
               37057787 37237967 38357928 39327864