Severe weather still a high probability this evening and tonight. Here’s the latest information from SPC on ongoing severe weather in Wisconsin and Iowa that could eventually impact the Chicago area

Mesoscale Discussion 1489
   NWS Storm Prediction Center Norman OK
   0540 PM CDT Wed Aug 11 2021

   Areas affected...Eastern IA...Southern WI...Northwest IL

   Concerning...Tornado Watch 424...

   Valid 112240Z - 120015Z

   The severe weather threat for Tornado Watch 424 continues.

   SUMMARY...Ongoing storms from eastern IA into southwest WI will
   continue to pose a short-term severe threat. The eastward extent of
   the threat this evening remains uncertain due to the impact of
   earlier convection across southern WI/northern IL. Storm coverage is
   being monitored for possible watch issuance across eastern IA.

   DISCUSSION...At 2230Z, a few intense cells are ongoing from eastern
   IA into southwest WI, within an environment characterized by large
   CAPE and effective shear of 25-35 kt. The mature storms in this
   region will continue to pose a short-term threat of locally damaging
   wind, hail, and perhaps a tornado or two into the early evening as
   they move eastward. 

   Downstream into south-central WI/northern IL, the impact of morning
   convection is still evident, with relatively strong MLCINH
   persisting per recent mesoanalyses and low-level stratus increasing
   in recent visible imagery. Ongoing storms may tend to struggle with
   time as they move eastward, especially given the relatively limited
   large-scale ascent as the primary vorticity maxima move
   northeastward away from the area. Low-level warm advection may
   promote an increase in storm coverage later this evening, though
   this scenario remains somewhat uncertain. 

   Meanwhile, across eastern IA, storm coverage remains uncertain into
   this evening, though with a conditionally favorable environment in
   place, watch issuance remains possible to the southwest of WW 424 if
   additional intense thunderstorm development appears imminent.

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