Subj : MESO: Mesoscale Discussion 1643
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Jul 20 2023 18:15:40

ACUS11 KWNS 201815
SWOMCD
SPC MCD 201815=20
NYZ000-PAZ000-OHZ000-MIZ000-INZ000-ILZ000-201945-

Mesoscale Discussion 1643
NWS Storm Prediction Center Norman OK
0115 PM CDT Thu Jul 20 2023

Areas affected...Extreme east-central IL into central/northern
IN/OH...far southern MI...northwest PA...western NY

Concerning...Severe potential...Watch likely=20

Valid 201815Z - 201945Z

Probability of Watch Issuance...95 percent

SUMMARY...The threat for severe thunderstorms will increase with
time this afternoon. One or more additional watches will likely be
needed soon.

DISCUSSION...At 18 UTC, cumulus is increasing along a cold front
from southwest lower MI into northwest IN, and also along a
prefrontal trough from extreme east-central IL into western IN. As a
well-defined midlevel shortwave trough moves across MI, confidence
is high in additional storm development along the cold front this
afternoon, with more scattered development possible near the
prefrontal trough. Diurnal heating of an increasingly moist
environment has resulted in MLCAPE increasing above 2000 J/kg across
much of the prefrontal environment, with moderate midlevel flow
supporting 40+ of effective shear, sufficient for organized clusters
and a few supercells.=20

Favorable buoyancy and relatively steep midlevel lapse rates will
support a hail threat with the initial more discrete development. A
tornado or two also cannot be ruled out with any sustained
supercell. With time, one or more upscale growing clusters may
evolve, with an increasing threat of damaging gusts.=20

Farther east, an isolated storm that produced 1-inch hail around
Erie, PA, near the lake breeze and along the leading edge of
returning low-level moisture. In the short term, an additional
strong storm or two may develop within this regime, with threat of
isolated hail and strong/damaging gusts. Storms associated with the
cold front (described above) will eventually move into this area by
late afternoon or evening.=20

Given the threats described above, one or more watches will likely
be needed soon.

...Dean/Hart.. 07/20/2023

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!4POs5uo7MfbD2tVmiJsewADpzy18JUcRsGZarGgP-ALyTboxQjvoNoLApmu6fXGrYIkvMWeHw=
-iqEeFfFW0k_JUZBQk$  for graphic product...

ATTN...WFO...BUF...CTP...PBZ...CLE...ILN...IWX...IND...LOT...
ILX...

LAT...LON   41678691 42018608 41988492 41688438 41728332 41988296
            42997859 42357827 41467944 40458152 39938399 39678681
            39838794 40218797 40468779 40988731 41678691=20


=3D =3D =3D
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