Storm Prediction Center Mesoscale Discussion 2054

   Mesoscale Discussion 2054
   NWS Storm Prediction Center Norman OK
   0326 PM CDT Thu Aug 20 2026

   Areas affected...parts of southeastern Pennsylvania...southern New
   Jersey...eastern Maryland and Delaware

   Concerning...Tornado Watch 605...

   Valid 202026Z - 202230Z

   The severe weather threat for Tornado Watch 605 continues.

   SUMMARY...An organizing cluster of storms will pose increasing
   potential to produce damaging wind gusts and a couple of tornadoes
   into and across the Greater Philadelphia vicinity through the the
   6-7 PM EDT time frame.

   DISCUSSION...A more prominent, but still compact, clustering of
   intensifying thunderstorm development is ongoing south/southeast of
   Harrisburg PA.  This does appear focused near a weak developing
   frontal wave, and is perhaps being supported by forcing for ascent
   downstream of an east-northeastward propagating 50+ kt mid-level jet
   streak, based on the latest Rapid Refresh output.

   Strongest recent boundary-layer destabilization, associated with
   insolation and thermal/moisture advection, has become focused to the
   north of the Greater Baltimore area the past few hours.  Updraft
   inflow emanating from this environment, probably will support
   further upscale growth and intensification of the convective system
   into and across the Greater Philadelphia area through 22-23Z.  This
   may include evolving supercell structures posing a risk for
   tornadoes, and increasing risk for strong to severe surface gusts.

   ..Kerr.. 08/20/2026

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

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

   LAT...LON   40137604 40567548 40477448 39757423 39187484 38917557
               39187615 39667641 40137604 

   MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN