Mesoscale Discussion 0269
   NWS Storm Prediction Center Norman OK
   0958 AM CDT Sun Mar 29 2020

   Areas affected...Parts of western New York and Pennsylvania

   Concerning...Severe potential...Watch possible 

   Valid 291458Z - 291700Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Scattered strong to severe thunderstorm development,
   including a couple of supercells, appears increasingly probable
   across parts of western Pennsylvania into western New York State
   during the 1-3 PM EDT time frame.  Trends are being monitored for
   the possibility of a severe weather watch.

   DISCUSSION...Boundary-layer heating and mixing is underway within a
   narrow pre-cold frontal corridor now spreading eastward across the
   lower Great Lakes/upper Ohio Valley region.  Surface observations at
   14Z indicate that dew points have increased to near 60F along an
   axis from Huntington WV nort-northeastward toward Ashtabula OH. 
   Latest model output suggests that this axis will shift into western
   Pennsylvania and New York by the 17-19Z time frame, when, with
   additional surface heating, the boundary layer may become
   increasingly conducive to deep boundary-layer based convective
   development.  Coinciding with the leading edge of strong mid-level
   height falls, the initiation of thunderstorm activity seems
   probable.

   Developing thunderstorms may remain mostly pre-frontal, scattered
   and discrete given apparent weak low-level forcing along the cold
   front.  However, mixed-layer CAPE increasing in excess of 1000 J/kg,
   in the presence of very strong deep-layer shear within the exit
   region of a 90 kt 500 mb jet streak, should be conducive to
   sustained supercells.  This will be accompanied by a risk for severe
   hail and locally damaging surface gusts.  Although low-level
   hodographs may initially be large and clockwise curved, forecast
   soundings indicate a transition to more unidirectional with time. 
   So, while a tornado or two might not be out of the question, this
   potential remains a little more unclear.

   ..Kerr/Thompson.. 03/29/2020

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

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

   LAT...LON   43777857 43487710 41697821 40607881 40287988 40768033
               42797980 43777857