116
ACUS11 KWNS 161646
SWOMCD
SPC MCD 161645
ILZ000-WIZ000-IAZ000-161845-

Mesoscale Discussion 1684
NWS Storm Prediction Center Norman OK
1145 AM CDT Wed Jul 16 2025

Areas affected...Far Eastern IA...Southern/Central WI...Northern IL

Concerning...Severe potential...Watch likely

Valid 161645Z - 161845Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorm intensity and coverage is expected to
increase from far eastern IA into southern/central WI and northern
IL this afternoon. All severe hazards will be possible with the more
mature/long-lived storms, including a few tornadoes.

DISCUSSION...Recent surface analysis places a low about 40 miles
east-northeast of ALO in far northeast IA. A warm front extends
northeastward from this low into south-central WI before arcing more
eastward and then southeastward into southern Lake Michigan.
Additionally, a surface trough extends southward from this low
across far eastern IA, while a cold front also extends southwestward
across south-central IA into central KS.

Modest mid-level warm-air advection attendant to the parent
shortwave trough has promoted surface-based thunderstorm within the
warm sector south of the warm front across far southwest WI and far
northwest IL. There is potential for this activity to strengthen as
the airmass downstream across central/southern WI destabilizes amid
filtered daytime heating. Additional thunderstorm development is
also possible along the surface trough as it pushes eastward into
the region this afternoon.

Ample low-level moisture within the warm sector is supporting
moderate buoyancy, despite poor mid-level lapse rates. Vertical
shear is enhanced by slightly stronger low to mid-level flow close
to the approaching shortwave. The resulting combination of
instability and shear will support organized storm structures,
including a few supercells. Low-level flow will be relatively
modest, but ample low-level instability and increased low-level
vorticity close to the surface low could still result in a few
tornadoes. Some isolated hail could also occur with the more
cellular storms, but damaging gusts will likely be the primary risk,
particularly with any bowing segments that materialize.

..Mosier/Smith.. 07/16/2025

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

ATTN...WFO...GRB...LOT...MKX...DVN...ARX...

LAT...LON   43369135 44089009 43948850 43168789 41988818 41519064
            43369135

MOST PROBABLE PEAK TORNADO INTENSITY...100-130 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN