Storm Prediction Center Mesoscale Discussion 1921

   Mesoscale Discussion 1921
   NWS Storm Prediction Center Norman OK
   0900 AM CDT Tue Aug 11 2026

   Areas affected...southern Wisconsin...northern Illinois...and far
   northwest Indiana

   Concerning...Severe Thunderstorm Watch 563...

   Valid 111400Z - 111600Z

   The severe weather threat for Severe Thunderstorm Watch 563
   continues.

   SUMMARY...The potential for significant wind gusts up to 75-85 mph
   is expected to persist with an evolving bow echo this morning.

   DISCUSSION...An MCS with a history of producing wind gusts of 70-80
   mph is currently evolving into a broader bowing configuration over
   east-central IA and far northwest IL as of 1355Z. The 12z DVN
   sounding is likely a good representation of the ambient inflow
   environment, featuring steep mid-level lapse rates and abundant
   boundary-layer moisture, yielding MUCAPE of 4500-5000 J/kg. A
   largely unidirectional wind profile with around 35 kt of deep-layer
   shear (per the 12z DVN sounding and current VWP) in conjunction with
   the strongly unstable environment is likely to support further
   intensification of the bow echo with an associated risk for
   significant wind gusts up to 75-85 mph. Around 30 kt of 0-3 km shear
   oriented largely perpendicular to the cold pool may support some
   tornado potential, especially where the low-level shear and cold
   pool remain in balance. 

   The bow echo is expected to track along a residual outflow boundary
   from a downstream MCS, which extends east-southeast through the
   south side of the greater Chicago metropolitan area into far
   northwest IN.

   ..Mead.. 08/11/2026

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

   ATTN...WFO...LOT...ILX...MKX...DVN...ARX...

   LAT...LON   41019100 41759134 42869123 43259046 42988895 42728791
               42168727 41348703 40718724 40268791 40358868 41019100 

   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN