Mesoscale Discussion 1610
   NWS Storm Prediction Center Norman OK
   0855 AM CDT Fri Aug 28 2020

   Areas affected...western/central/southeast PA...northern
   MD...northern DE

   Concerning...Severe potential...Watch possible 

   Valid 281355Z - 281630Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Strong to severe thunderstorms, potentially capable of
   55-65 mph gusts, are possible beginning this morning (on a localized
   basis) but becoming potentially more widespread east of the
   mountains into portions of southeast PA.  A severe thunderstorm
   watch will likely need to be considered at some point later this
   morning for southeast PA and perhaps adjacent parts of central PA
   and MD/DE/NJ.    A Slight Risk will be included for portions of the
   Mid-Atlantic states in the upcoming 1630z convective outlook.

   DISCUSSION...Radar mosaic shows a cluster of thunderstorms over
   northwest PA into northeast OH driven primarily be low-level warm
   advection near the remnants of west-northwest to east-southeast
   oriented thunderstorm outflow from Thursday evening.  The 12z
   Pittsburgh observed sounding again was very moist with a lowest 100
   mb mean mixing ratio of 14.9 g/kg and 1100 J/kg MLCAPE.  The wind
   profile sampled by the Pittsburgh sounding/KPBZ VAD showed moderate
   westerly flow and around 25-30 kt effective shear.  The wind profile
   farther east at KLWX, KDIX, and KDOX is similar.  

   13z surface observations show lower 70s temperatures in western and
   central PA but temperatures have already warmed to near 80 F east of
   the terrain in MD and southeast PA.  Current expectation is for this
   cluster of storms to continue east-southeast and for it to encounter
   a gradually destabilizing airmass with MLCAPE rising into the
   1500-2000 J/kg range.  Recent HRRR model guidance depict a similar
   convective evolution.  Concurrently, the propensity for strong to
   locally severe gusts should become more widespread with time.

   ..Smith/Grams.. 08/28/2020

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

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

   LAT...LON   41258000 41457962 40197532 39437555 39077632 40288006
               40798028 41258000