MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN

ACUS11 KWNS 261723
SWOMCD
SPC MCD 261722 
MIZ000-OHZ000-INZ000-ILZ000-261915-

Mesoscale Discussion 2137
NWS Storm Prediction Center Norman OK
1222 PM CDT Wed Aug 26 2026

Areas affected...portions of the eastern Corn Belt into southern
Lower Michigan

Concerning...Severe potential...Watch possible 

Valid 261722Z - 261915Z

Probability of Watch Issuance...40 percent

SUMMARY...Thunderstorms forming along/ahead of an approaching cold
front may pose a risk for damaging wind gusts and large hail this
afternoon and evening. Watch issuance is possible.

DISCUSSION...Latest surface analysis places an occluded low across
southern Ontario with a cold front extending south-southwestward
across Lake Michigan and into central Illinois as of 1700 UTC.
Dewpoints generally range from the low to mid-60s F ahead of this
front, with modest moisture pooling and greater dewpoints (low 70s
F) noted in the immediate vicinity of the boundary across central
IL. As this front progresses eastward through the afternoon, ongoing
surface heating and southeasterly low-level theta-e advection will
yield an eastward transition of a relatively narrow and
destabilizing corridor of 1000 to locally 2000 J/kg MLCAPE.

Expectation is for some intensification to occur with ongoing
convection across southwestern Michigan over the next 1-2 hours,
with additional initiation likely farther southwest along the cold
front (where deepening cumulus are currently noted on visible
satellite imagery). Effective shear of 25-30 kts is sufficient to
support multicellular clusters and perhaps marginal supercell
structures capable of primarily damaging wind gusts (generally 50-60
mph) and large hail. A brief tornado cannot be ruled out, but veered
low-level winds should largely temper this risk. The need for a
watch remains somewhat unclear owing to generally limited effective
shear and thus uncertainty regarding overall convective intensity.

..Chalmers/Mosier.. 08/26/2026

ATTN...WFO...CLE...ILN...DTX...IWX...GRR...IND...LOT...ILX...

LAT...LON   40368862 41188786 42408573 42748445 42738393 42598358
            42368334 42008333 41458359 40758449 39838619 39558678
            39468741 39468783 39598824 39748853 39998866 40368862 

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN

$$

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