Severe thunderstorm possible this afternoon and evening… Mesoscale discussion issued for portions of northern and central Illinois

Severe Weather Updates

 Mesoscale Discussion 0680
   NWS Storm Prediction Center Norman OK
   1129 AM CDT Sat May 23 2020

   Areas affected...eastern Iowa into much of northern and central
   Illinois

   Concerning...Severe potential...Watch possible 

   Valid 231629Z - 231830Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Bands of convection continue to increase in coverage near
   the Quad Cities and also farther west between Des Moines and Cedar
   Rapids.  As storms become surface-based, an increasing tornado and
   damaging-wind threat will evolve.

   DISCUSSION...Lift with and advancing mid-level low and
   insolation/surface heating aiding in a gradual expansion in
   convective coverage this morning - particularly in a couple of bands
   across western portions of the discussion area.  A few additional
   updrafts were also noted across west-central Illinois near Quincy. 
   These trends should continue advancing mid/upper low migrates
   eastward in tandem with a destabilizing boundary layer.  A surface
   low centered near Des Moines will aid in keeping surface winds
   backed through the remainder of the morning - especially in northern
   Illinois.   Despite modest low-level flow (generally between 15-30
   knots areawide) and MUCAPE only reaching 1000-1500 J/kg during the
   day, backed surface winds and veering kinematic profiles with height
   suggest potential for cells in this regime to rotate.  As cells
   continue to migrate northeastward through the afternoon, they will
   gradually become more surface-based and pose more of a threat for
   tornadoes and a few damaging wind gusts.  Some hail may also occur
   near the strongest updrafts.

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