Mesoscale Discussion 1882
   NWS Storm Prediction Center Norman OK
   0656 PM CDT Thu Oct 21 2021

   Areas affected...Portions of western Pennsylvania

   Concerning...Severe potential...Watch unlikely 

   Valid 212356Z - 220200Z

   Probability of Watch Issuance...20 percent

   SUMMARY...The threat for a couple of tornadoes is expected to
   persist for a couple more hours before storms weaken and the severe
   threat gradually diminishes. Given the expected short duration
   tornado threat, a Tornado Watch issuance remains unlikely.

   DISCUSSION...Multiple discrete/semi-discrete supercells continue to
   exhibit instances of strong low-level rotation, from Butler County
   PA to Ohio County WV. Multiple TDS signatures were noted with some
   of these storms in the past few minutes via KPBZ dual-polarimetric
   radar data. These storms continue to rotate within an environment
   characterized by weak buoyancy (MLCAPE barely reaching 500 J/kg
   MLCAPE), but with strong low-level shear. Specifically, PBZ VAD
   profiler data have shown consistent elongated hodographs with 200+
   0-1km SRH, with METAR observations also showing some localized
   backing of the surface winds across southwest PA. As such, storm
   organization and periods of low-level rotation/brief tornadoes will
   likely continue for a couple more hours, before boundary-layer
   stabilization results in a gradual waning of the severe threat. A
   Tornado Watch issuance is not expected.

   ..Squitieri/Dial.. 10/21/2021

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

   ATTN...WFO...CTP...PBZ...

   LAT...LON   39718099 40388039 41097992 41307939 41307862 41137820
               40797816 40637825 40247871 39977907 39817933 39727973
               39628048 39718099