Mesoscale Discussion 1117
NWS Storm Prediction Center Norman OK
0823 PM CDT Sat Jun 26 2021
Areas affected...east-central Illinois northeast into Lower Michigan
Concerning...Tornado Watch 322...
Valid 270123Z - 270230Z
The severe weather threat for Tornado Watch 322 continues.
SUMMARY...Overall convective trends indicate a diminishing threat of
organized severe potential. Brief/localized gusty winds may be
possible across portions of the region, but the isolated nature of
the threat should not preclude the expiration of Tornado Watches 321
and 322 at 10PM EDT and 9 PM CDT.
DISCUSSION...A small convective bowing segment is expected to
continue weakening as it moves across Lower Michigan this evening.
This is supported by a substantial decrease in lightning activity
and warming cloud tops as the segment moves into an airmass already
overturned by earlier convection. Gusty winds may continue to occur
over the next 1-2 hours as the segment continues to move northeast,
between Lansing and Ann Arbor, but given the overall downward
trends, Tornado Watch 322 should be able to expire at 02Z.
Farther south, a more robust convective bowing segment has developed
as it exited portions of east-central Illinois and (locally
extended) Tornado Watch 321 and into west-central Indiana and Severe Thunderstorm Watch 325. However, the loss of diurnal heating and
development of a nocturnal boundary layer should begin to increase
near-ground stability sufficiently to decrease the likelihood of
sustained severe-criterion surface winds with time. Before this
happens, strong, gusty thunderstorm winds will continue to be
possible for the next couple of hours. Otherwise, convective
intensity continues to diminish across Tornado Watch 321 and thus
the watch should be able to expire at 02Z.
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