SPC MD 1882

MD 1882 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF WESTERN PENNSYLVANIA
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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 

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