Mesoscale Discussion 0511
   NWS Storm Prediction Center Norman OK
   1147 AM CDT Mon Apr 21 2025

   Areas affected...parts of nern OH...nwrn PA...swrn NY State

   Concerning...Severe potential...Watch unlikely 

   Valid 211647Z - 211915Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Strengthening low-topped thunderstorm development appears
   probable by 3-5 PM EDT, including isolated to widely scattered
   supercells accompanied by small to marginally severe hail and at
   least some risk for a tornado.  It is not clear that a severe
   weather watch will be needed, but trends are being monitored.

   DISCUSSION...Within the warm sector of an occluding cyclone
   migrating northeastward across the upper peninsula of Michigan,
   boundary-layer destabilization is ongoing within at least a narrow
   corridor across eastern Ohio into the lower Great Lakes vicinity. 
   Closely trailing an initial band of weak mid-level warm advection
   driven convection, which has contributed to saturation of initially
   dry lower/mid-tropospheric profiles, boundary-layer moisture
   characterized by dew points near 60f, is rapidly advecting
   northeastward.  This is occurring beneath the leading edge of a
   mid-level dry slot, which is allowing for increasing insolation. 
   The NAM and Rapid Refresh suggest that this will contribute to
   mixed-layer CAPE on the order of 500 J/kg, prior to the passage of
   the cold front.

   This is also occurring beneath a 30-50 kt south-southwesterly 850 mb
   jet axis, where forecast soundings indicate enlarged low-level
   hodographs may include modest clockwise curvature of the shear
   vector with height by peak destabilization.  As mid/upper forcing
   for ascent (downstream of the base of a negatively tilted short wave
   advancing toward the region) supports deepening convective
   development, there appears a window of opportunity for scattered
   low-topped supercell development by 19-21Z.  This may be accompanied
   by a risk for small to marginally severe hail, locally strong
   surface gusts, and at least potential for a tornado or two.

   ..Kerr/Hart.. 04/21/2025

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

   ATTN...WFO...BUF...CTP...PBZ...CLE...

   LAT...LON   42887905 42497783 41857867 40827995 40408114 40938153
               41898069 42887905 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN