Mesoscale Discussion 0410
   NWS Storm Prediction Center Norman OK
   0459 PM CDT Fri Apr 19 2019

   Areas affected...Southern PA

   Concerning...Severe potential...Watch possible 

   Valid 192159Z - 200000Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Some increase in the threat for damaging wind and perhaps
   a tornado or two is possible into this evening. The area is being
   monitored for possible watch issuance.

   DISCUSSION...Widespread cloudiness has thus far limited
   destabilization and thunderstorm coverage across much of PA.
   However, deep-layer southerly flow has allowed substantial
   moistening to occur, with dewpoints now into the mid 60s F across
   southern PA, sufficient to support MLCAPE of 250-500 J/kg per recent
   objective mesoanalyses. As stronger convection currently across VA
   and the eastern WV panhandle spreads northward, some increase in the
   severe thunderstorm threat is expected into at least southern PA.
   Strong low-level southerly flow (40 kt or greater just above the
   surface) will support a threat of damaging wind with the strongest
   storms, while very favorable low-level shear/helicity will support a
   threat of a tornado or two. 

   The primary uncertainty across this area is the ability of
   convection to maintain its intensity as it spreads into a region of
   very limited buoyancy. This renders the need for a watch uncertain
   at this time, but watch issuance is possible if it appears that
   organized convection to the south will be sustained as it moves into
   southern PA.

   ..Dean/Hart.. 04/19/2019

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

   ATTN...WFO...PHI...CTP...

   LAT...LON   39737859 40217841 40507794 40517675 40377601 40137580
               39857588 39757600 39767690 39757779 39737859