Storm Prediction Center Mesoscale Discussion 1684

   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