Mesoscale Discussion 1775

Issued

Sep 22, 2021, 1:08 PM EDT (17:08 UTC)

Expired

Sep 22, 2021, 3:45 PM EDT

In force

3 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

The Pittsburgh radar (KPBZ), 36 km from the middle of the area, began a volume at 17:10 UTC, the scan nearest the moment this went out.

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• Tornado Watch 510Sep 22, 2:20 PM EDT

249 
ACUS11 KWNS 221709
SWOMCD
SPC MCD 221708 
PAZ000-WVZ000-OHZ000-221945-

Mesoscale Discussion 1775
NWS Storm Prediction Center Norman OK
1208 PM CDT Wed Sep 22 2021

Areas affected...Portions of eastern OH...western PA...and northern
WV

Concerning...Severe potential...Watch possible 

Valid 221708Z - 221945Z

Probability of Watch Issuance...40 percent

SUMMARY...A threat for damaging winds and perhaps a couple of
tornadoes may increase this afternoon as storms develop. Watch
issuance is possible.

DISCUSSION...Partly sunny conditions are present this afternoon
ahead of a cold front across eastern OH into western PA and
northern/central WV. With surface dewpoints mainly in the mid to
upper 60s across the warm sector, continued diurnal heating of this
moist low-level airmass will likely foster at least weak
destabilization this afternoon. MLCAPE generally ranging from
1000-1500 J/kg should develop by peak afternoon heating in a couple
of hours, even though mid-level lapse rates will remain poor. Both
low and mid-level southerly winds will strengthen this afternoon
across the warm sector as a nearly closed upper low moves slowly
eastward across the OH Valley. Increasing large-scale ascent
associated with the exit region of a mid/upper-level jet and modest
low-level convergence along the surface cold front will aid the
development of scattered to numerous storms this afternoon. Even
with a largely meridional component to the low/mid-level flow,
around 40-45 kt of effective bulk shear should support storm
organization, with both a linear and supercell mode possible.
Damaging winds should be the main threat if a linear mode along the
cold front dominates, as some high-resolution guidance suggests. A
couple of tornadoes may also occur, particularly with any supercell
that develops where surface winds are backed to a more southeasterly
component, locally enhancing 0-1 km SRH. Watch issuance is possible
this afternoon, pending signs of increasing storm coverage and
intensity.

..Gleason/Hart.. 09/22/2021

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

ATTN...WFO...PBZ...RLX...CLE...

LAT...LON   40618173 41688146 41948076 42068017 41077896 40347910
            39417987 38828100 38888168 40618173

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.