Mesoscale Discussion 1023
   NWS Storm Prediction Center Norman OK
   1134 AM CDT Sat Jun 27 2020

   Areas affected...eastern Pennsylvania and northern New Jersey into
   Long Island and southern Connecticut

   Concerning...Severe potential...Watch possible 

   Valid 271634Z - 271900Z

   Probability of Watch Issuance...40 percent

   SUMMARY...At least isolated strong to severe storms capable of
   damaging wind gusts or marginal hail are expected to form after 17Z,
   and will progress east/southeast toward the coast later this
   afternoon.

   DISCUSSION...Surface analysis shows veering winds across western PA,
   west of a deepening surface trough over eastern NY and PA. Nearly
   parallel to the winds a loft, a convergence zone oriented WNW to ESE
   is noted over central PA with associated showers, while rain
   persists from northeast PA into NY.

   Temperatures are warming quickly south of these showers across
   southern PA, MD and VA, and west/southwest 850 mb winds of 25-35 kt
   will aid destabilization northeastward toward the rain-cooled areas.
   A zone of 200 m2/s2+ effective SRH also exists along the warm/cool
   air interface, and this should translate east today as the warmer
   air spreads into eastern PA, NJ, and NY.

   Around 1000 J/kg MLCAPE is expected to develop over the next few
   hours where temperatures warm into the 80s, beneath modest westerly
   flow aloft. Since this area is behind the primary midlevel
   disturbance, lift will be driven mainly by warm advection, with at
   least isolated storms forming along or ahead of the aforementioned
   convergence zone over PA. A broken line of storms is possible,
   producing damaging wind gusts given favorable deep-layer mean winds.
   A supercell is possible as storms interface with the larger SRH area
   along the warm/cool air interface as well, and a brief/weak tornado
   could not be ruled out.

   With time, greater instability may spread northeastward into Long
   Island and CT, supporting isolated strong or severe storms.

   ..Jewell/Thompson.. 06/27/2020

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

   ATTN...WFO...OKX...PHI...BGM...CTP...

   LAT...LON   40227698 40537748 40877722 41137646 41247541 41347413
               41297336 40947297 40607313 40447381 39887399 39707423
               39927528 40067606 40227698