SPC MD 2024

Mesoscale Discussion 2024
NWS Storm Prediction Center Norman OK
0152 PM CDT Tue Aug 18 2026

Areas affected...Northern Iowa into southeast Minnesota and
southwestern Wisconsin

Concerning...Severe potential...Watch likely 

Valid 181852Z - 182045Z

Probability of Watch Issuance...80 percent

SUMMARY...Large hail (some around 2 in.) and damaging winds will be
possible with scattered storms in the Upper Midwest. A watch is
likely this afternoon.

DISCUSSION...A weak MCV and associated cloud cover is present within
much of central/southern Wisconsin this afternoon. That said, strong
heating is occurring near a surface trough in northeast Iowa.
Thunderstorms have recently developed but have thus far not been
able to mature. Continued destabilization into southwestern
Wisconsin may allow this activity to pose an increasing severe
threat over the next couple of hours. Convective coverage is also
expected to increase along the cold front, though this may be
delayed until later this afternoon given the cloud cover. Moderately
strong mid-level winds on the southern flank of the upper-level low
is supporting around 40-45 kt of effective shear. Hodographs are
long and straight which suggests splitting supercells. Large hail
(with hail to around 2 inches possible, particularly in the
westernmost areas where mid-level lapse rates are steeper) and
damaging winds will be possible this afternoon.

..Wendt/Guyer.. 08/18/2026

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

ATTN...WFO...GRB...MKX...DVN...ARX...MPX...DMX...

LAT...LON   42579070 42349238 42389302 42499334 43029352 43669364
            44319313 44689080 44338997 43978961 42968992 42579070 

MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

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