Storm Prediction Center Mesoscale Discussion 453

   Mesoscale Discussion 0453
   NWS Storm Prediction Center Norman OK
   1108 AM CDT Tue Apr 15 2025

   Areas affected...parts of nrn PA...srn NY

   Concerning...Severe potential...Watch unlikely 

   Valid 151608Z - 151915Z

   Probability of Watch Issuance...5 percent

   SUMMARY...Showers and embedded thunderstorms accompanied by gusty
   winds occasionally approaching or briefly exceeding severe limits
   are possible into the 2-4 PM EDT time frame, particularly in a
   corridor across north central Pennsylvania toward the Catskills and
   Poconos.

   DISCUSSION...Boundary-layer destabilization is ongoing within a
   narrow corridor across the upper Ohio Valley into lower Great Lakes
   region.  This is generally focused beneath the leading of stronger
   mid-level forcing for ascent and cooling associated with large-scale
   troughing overspreading the region.  Thermodynamic profiles have
   become increasingly conducive to the initiation of scattered
   low-topped thunderstorm activity, and this probably will continue
   this afternoon with further boundary-layer warming and mixing with
   insolation.  

   The last Rapid Refresh suggests that the corridor of stronger
   mid-level cooling and weak boundary-layer destabilization will
   gradually shift east-northeastward across northern Pennsylvania and
   southern New York State through 18-20Z.  This may include CAPE
   increasing only to the order of a couple hundred J/kg for a
   seasonably cool boundary layer.  However, steepening low-level lapse
   rates, with profiles characterized by modest temperature/dew point
   spreads, will contribute to sub-cloud evaporative cooling and
   melting, and aid downward transfer of momentum associated with
   strengthening westerly flow (on the order of 30-40 kt) in the
   850-700 mb layer.

   ..Kerr/Guyer.. 04/15/2025

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

   ATTN...WFO...ALY...BGM...BUF...CTP...PBZ...

   LAT...LON   42837591 43187450 42547412 42027412 40927731 41097943
               42207838 42837591 

   MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN