Mesoscale Discussion 1313
   NWS Storm Prediction Center Norman OK
   1245 PM CDT Wed Jul 22 2020

   Areas affected...portions of eastern PA...NJ...southern NY and
   southern New England

   Concerning...Severe potential...Watch possible 

   Valid 221745Z - 221945Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Scattered thunderstorms will increase in coverage and
   intensity through the afternoon. Strong, locally damaging gusts will
   be possible with these storms into this evening.

   DISCUSSION...A broad area of deepening cumulus continues to develop
   across portions of eastern PA/NJ northeastward into southern New
   England ahead of a shortwave vorticity max. At the surface, a warm
   front extends from central NY east/southeast into CT/RI. South of
   the front, surface dewpoints are mainly in the 70s F and strong
   heating has allowed temperatures to warm into the mid to upper 80s
   F. As a result, a tongue of MLCAPE from 500-1500 J/kg resides from
   eastern PA and NJ northward into southern NY and western CT. The
   warm front should progress northward a bit more through the
   afternoon and at least weak destabilization is expected as far north
   as southern VT/NH into western/central MA. 

   In addition to weak to moderate instability, moderate deep shear
   resides over the region, and effective bulk shear around 35-45 kt
   should overspread the entire MCD area by late afternoon. Some
   uncertainty with regards to convection initiation remains, largely
   due to weak forcing across the area. A vorticity max further east
   near Lakes Erie/Ontario should spread eastward with time, but
   initial convective development may be largely driven by diurnal
   processes, especially over southern portions of the MCD area from
   far southern NY/Long Island southward into NJ. Nevertheless, the
   overall environment should support organized cells and clusters,
   once they develop. Midlevel lapse rates will remain modest, but
   strong heating has resulted in steep low level lapse rates south of
   the warm front, and PW values greater than 1.75 inches will further
   aid in strong downburst potential. 

   While timing of convection remains a bit uncertainty, at least
   sporadic instances of severe gusts and locally damaging winds are
   expected into the evening hours, and a watch may be needed this
   afternoon, within the next few hours.

   ..Leitman/Hart.. 07/22/2020

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

   ATTN...WFO...GYX...BOX...OKX...ALY...PHI...BGM...CTP...

   LAT...LON   40347571 41117585 41827548 42537507 43087463 43367398
               43227301 42787239 42007205 41797217 41437235 40797273
               40587307 40237346 39777424 39807486 40207544 40347571