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Mesoscale Discussion 1458
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   Mesoscale Discussion 1458
   NWS Storm Prediction Center Norman OK
   0336 PM CDT Mon Aug 10 2020

   Areas affected...Portions of northern/central IL...far southeastern
   WI...northwestern IN...and far southwestern Lower MI

   Concerning...Severe Thunderstorm Watch 426...429...

   Valid 102036Z - 102200Z

   The severe weather threat for Severe Thunderstorm Watch 426, 429

   SUMMARY...A widespread severe/damaging wind threat continues with a
   line of storms moving quickly eastward. A tornado also remains
   possible. The greatest threat for 70-80+ mph wind gusts will likely
   focus over the Chicago metro area over the next hour.

   DISCUSSION...Latest velocity data from KLOT shows somewhat less
   extreme inbound velocities (generally 50-80 kt) compared to earlier.
   Even so, the overall bow echo remains well organized, and it is
   moving through a very strongly unstable airmass (3500-4000+ J/kg
   MLCAPE). A severe wind gust to 54 kt was observed in Aurora IL at
   2016Z. The northern portion of the bow will have the best potential
   to continue producing widespread damaging wind gusts as it moves
   across the Chicago metro area over the next hour, with some possibly
   still significant (75-80+ mph). A tornado or two embedded within the
   line also remains possible across this area, but the primary risk is
   still widespread damaging straight-line winds. This substantial
   severe wind threat will likely continue across southern Lake
   Michigan and into southwestern Lower MI and northwestern IN late
   this afternoon and into the early evening given a favorable
   combination of moderate to strong instability present across these

   The southern portion of the line into central IL has shown less
   intensity recently, with outflow beginning to surge southeastward
   ahead of the updrafts. This is likely due to weaker mid-level flow
   with southward extent across central IL (see recent VWPs from KILX).
   Still, isolated damaging winds will remain possible across this area
   in the short term.

   ..Gleason.. 08/10/2020

   ...Please see for graphic product...


   LAT...LON   40378880 40548971 41108914 42008878 42528895 43048858
               43088611 42778558 41128626 40808664 40548725 40378880 

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