210
ACUS11 KWNS 230343
SWOMCD
SPC MCD 230343
MIZ000-INZ000-ILZ000-230545-

Mesoscale Discussion 1381
NWS Storm Prediction Center Norman OK
1043 PM CDT Sat Jun 22 2024

Areas affected...parts of west central through northern
Illinois...southwestern lower Michigan...northwestern Indiana

Concerning...Severe Thunderstorm Watch 447...

Valid 230343Z - 230545Z

The severe weather threat for Severe Thunderstorm Watch 447
continues.

SUMMARY...An evolving line of storms may pose some further increase
in potential for strong to severe surface gusts for another hour or
two.  But this appears likely to diminish after around 1 or 2 AM
CDT, as storms weaken while continuing east-southeastward through
the southern Great Lakes/Ohio Valley vicinity.  A new severe weather
watch is not anticipated, but trends will continue to be monitored.

DISCUSSION...Convection has been gradually consolidating into a line
generally coincident with strengthening low-level frontogenetic
forcing.  This trails a developing surface cyclone now migrating
across Lake Michigan into lower Michigan, and will continue to
slowly advance east-southeastward across the southern Lake Michigan
and northern Illinois vicinity into the overnight hours.

Although subtle low-level moisture return is still possible
immediately ahead the evolving line, beneath a 30-40 kt
west-southwesterly jet around 850 mb, the downstream boundary-layer,
in general, is somewhat drier and characterized by increasingly weak
potential instability beneath relatively warm mid-level air.   So,
it appears that ongoing convection could maintain intensity, or
perhaps intensify a bit further, with sub-cloud evaporative cooling
contributing to downward mixing of momentum and a few strong to
severe surface gusts during the next couple of hours.  However,
beyond 06-07Z, this seems likely to diminish as convection begins to
weaken.

..Kerr.. 06/23/2024

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

ATTN...WFO...IWX...GRR...LOT...ILX...LSX...DVN...

LAT...LON   41419007 41668932 41848824 42018665 42558619 42358539
            41258707 40818876 40019060 40789076 41129045 41419007