ACUS11 KWNS 181638
SWOMCD
SPC MCD 181637
OHZ000-MIZ000-INZ000-ILZ000-181830-

Mesoscale Discussion 1647
NWS Storm Prediction Center Norman OK
1137 AM CDT Sat Jul 18 2026

Areas affected...Southern Michigan into northeast
Illinois...northern Indiana...and northwest Ohio

Concerning...Severe potential...Watch possible

Valid 181637Z - 181830Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms developing along a cold front will continue
to intensify and pose a risk for large hail and severe winds through
the afternoon across portions of the Great Lakes/Midwest. Watch
issuance is being considered and may be needed within the hour.

DISCUSSION...Latest radar mosaics and GOES imagery shows maturing
convection along and just ahead of a southeastward moving cold front
with a few deeper, more robust updrafts noted across eastern lower
MI and southwest lower MI. Downstream of this developing convection, temperatures continue to warm into the 80s within a moist air mass.
With further diurnal heating expected through late afternoon, MLCIN
will continue to erode as MLCAPE increases into the 2500-3000 J/kg
range. Additionally, regional VWPs are sampling 35-40 knot mid-level
flow over MI/OH with decreasing winds with westward extent. This
flow should remain in place through the day as a mid-level wave
continues to progress east/southeast towards the lower Great Lakes.

Given these convective and environmental trends, the expectation is
for additional thunderstorm development through the next few hours
with a steady uptick in intensification. Sufficient deep-layer shear
will promote organized storm modes, including the potential for a
few supercells initially (especially across MI) before frontal
ascent promotes increased clustering through late afternoon.
Consequently, some hail threat will likely materialize before
damaging/severe winds become the predominant threat through time
across IN and OH. Convective trends are being monitored, and watch
issuance will is probable as thunderstorm coverage continues to
increase.

..Moore/Thompson.. 07/18/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!8D8R2FDC-86UqCneQkW7NkB_VftTSlzu6ljXSLKlplx4K0nCeO8M8w3_uRXUWqBrLSK04OrQBv7TVO0HBApDI5dwMzQ$ for graphic product...

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

LAT...LON 40098729 40398838 40788880 41218885 41608871 41788841
41898744 42108638 42438516 42748447 43278358 43518288
43448249 43248225 42738223 41768210 41038228 40438264
40088349 40098729

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


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--- scorpsmtpd
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