Storms finally developing as cold front approaches the Chicago area.. some severe weather still possible

Mesoscale Discussion 1681
   NWS Storm Prediction Center Norman OK
   0932 PM CDT Sun Sep 06 2020

   Areas affected...Eastern IA...Northern IL

   Concerning...Severe potential...Watch possible 

   Valid 070232Z - 070430Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Isolated strong/severe thunderstorms are possible across
   eastern Iowa and northern Illinois over the next several hours.
   Large hail would be the primary risk.

   DISCUSSION...Southern influence of upper Great Lakes short-wave
   trough will glance eastern IA/northern IL over the next few hours.
   Latest IR imagery suggests deeper convection is beginning to evolve
   ahead of the front with showers now evident from north of DVN into
   extreme southeast WI. This activity is evolving within a fairly
   moist, but capped boundary-layer environment where MLCAPE is in
   excess of 2000 J/kg. 00z sounding from DVN appears to have sampled
   this pre frontal air mass well, and strong capping is evident near
   750mb. However, large-scale forcing for ascent along with a focused
   LLJ suggest sustained elevated convection may materialize along this
   corridor. Latest CAMs support this as well and there is increasing
   concern that a few storms may strengthen enough to produce hail.
   Will continue to monitor this region for possible severe
   thunderstorm watch.


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