Mesoscale Discussion 1778
   NWS Storm Prediction Center Norman OK
   0513 PM CDT Wed Sep 22 2021

   Areas affected...Western PA...Extreme Western NY

   Concerning...Tornado Watch 510...

   Valid 222213Z - 222345Z

   The severe weather threat for Tornado Watch 510 continues.

   SUMMARY...Severe threat is advancing downstream across western PA
   into extreme western NY. Primary threat for damaging winds, along
   with a tornado to two, will be over the next 1-2 hours.

   DISCUSSION...Well-defined squall line has evolved over western PA
   ahead of a strong short-wave trough that is ejecting across the OH
   Valley. Partial heating has contributed to a narrow corridor of
   instability that currently extends across western PA. Squall line
   will surge past this buoyancy axis over the next 1-2 hours and
   should begin to entrain cooler air which should lead to gradual
   weakening. However, latest radar imagery depicts a well-defined MCV
   over southeast Mercer County PA, lifting north-northeast toward the
   western counties of NY. Embedded circulations are noted along the
   squall line, immediately ahead of this feature. There is some
   concern this activity could remain severe for the next 50-70 miles
   which would be just beyond the edge of the current watch. Given the
   poor air mass downstream, and the limited area where severe appears
   possible, current thinking is a new watch may not be warranted.

   ..Darrow.. 09/22/2021

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

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

   LAT...LON   39817947 40847986 41808064 42488006 42277902 40517873
               39817947