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.
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