671
ACUS11 KWNS 050201
SWOMCD
SPC MCD 050201
MIZ000-OHZ000-INZ000-ILZ000-WIZ000-050500-

Mesoscale Discussion 2237
NWS Storm Prediction Center Norman OK
0901 PM CDT Fri Sep 04 2026

Areas affected...parts of southeastern Wisconsin...northeastern
Illinois...southwestern Lower Michigan...northern Indiana and
northwestern Ohio

Concerning...Severe potential...Watch possible

Valid 050201Z - 050500Z

Probability of Watch Issuance...40 percent

SUMMARY...Initially scattered intensifying thunderstorm development,
posing some risk to produce marginally severe hail and locally
strong surface gusts, is possible through 10 PM-midnight.  There
appears potential for activity to eventually consolidate and evolve
into an organized cluster with increasing risk to produce a swath of
strong to severe surface gusts later this evening or overnight.
Trends are being monitored for the possibility of a severe weather
watch.

DISCUSSION...An apparent mesoscale cyclonic vorticity center,
associated with an earlier small cluster of storms over northeastern
Iowa, is now approaching areas to the north-northwest of Rockford IL
with a renewed increase in convective development slowly underway.
This appears generally focused near and just to the warm side of a
quasi-stationary/slow moving low-level baroclinic zone extending
east-southeastward across southern portions of Lake Michigan/Lower
Michigan/northern Indiana and northwestern Ohio.  Downstream, to the
cool side of the frontal zone, low-level warm advection also appears
to be contributing to a gradual increase in convective development.

Thermodynamic profiles along this zone are relatively warm, but with
high low-level moisture content and characterized by at least
modestly steep lower/mid-tropospheric lapse rates supporting large
CAPE.  Coupled with favorable shear beneath modest northwesterly
mid-level flow along the southwestern periphery of the westerlies,
the environment appears conducive to gradually increasing and
intensifying thunderstorm development over the next few hours.  This
may eventually consolidate and organize into a cluster with
increasing potential to produce damaging surface gusts later this
evening across southern portions of the Great Lakes region, or
overnight into the middle Ohio Valley.

..Kerr/Smith.. 09/05/2026

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

ATTN...WFO...DTX...IWX...GRR...LOT...MKX...

LAT...LON   42858882 42868609 42398464 41898396 41248427 40938483
            40898503 40918610 41338767 41988920 42298884 42858882

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN