Mesoscale Discussion 1641
   NWS Storm Prediction Center Norman OK
   0118 PM CDT Sun Aug 29 2021

   Areas affected...Northern Illinois and far Northwestern Indiana

   Concerning...Severe potential...Watch unlikely 

   Valid 291818Z - 291945Z

   Probability of Watch Issuance...20 percent

   SUMMARY...A few multicell storms capable of isolated damaging wind
   gusts possible this afternoon.

   DISCUSSION...Regional radar show a line of storms that have
   initiated along a cold front across northern and northwestern
   Illinois. Minimal cloud cover this morning has allowed the
   downstream surface environment to warm rapidly into the mid 80s F
   amid rich low-level moisture (dew point temperatures in the low 70s
   F). This has allowed the atmosphere to destabilize, resulting in
   MLCAPE values near 2000-2500 J/kg. Low-level winds are veered ahead
   of the front and forecast soundings indicate predominately
   unidirectional shear profiles. This area is situated along the
   southern periphery of the advancing mid-level trough, and thus,
   generally weak flow aloft is yielding little in the way of
   deep-layer shear (effective bulk shear perhaps approaching 20 kt).
   Nevertheless, continued heating through the afternoon may yield
   low-level lapse rates near 7 C/km sufficient to aid in the threat
   for localized damaging wind gusts with any multicell clusters that
   are able to persist along the advancing front this afternoon.

   ..Karstens/Grams.. 08/29/2021

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

   ATTN...WFO...IND...LOT...ILX...MKX...DVN...

   LAT...LON   40278979 41089065 42018914 42978811 42688760 41478713
               40538741 40118799 40278979