Mesoscale Discussion 1889
   NWS Storm Prediction Center Norman OK
   0115 AM CST Wed Dec 30 2020

   Areas affected...Portions of northern IL...far southeastern WI...far
   northern IN...and southern Lower MI

   Concerning...Winter mixed precipitation 

   Valid 300715Z - 301315Z

   SUMMARY...A mix of freezing rain, sleet, and snow will move west to
   east this morning while gradually transitioning to all rain.
   Freezing rain rates may exceed 0.05 inch per 3 hours across parts of
   southern Lower Michigan.

   DISCUSSION...Ahead of a positively tilted mid/upper-level trough,
   strong ascent associated with a 50-60+ kt southwesterly low-level
   jet is supporting a broad swath of precipitation across the Midwest
   early this morning. Multiple sites across northern IL and vicinity
   are reporting freezing rain as the predominant precipitation type,
   with some locations recording ice accretion in excess of 0.05 inch
   in 3 hours. Current expectations are for this moderate to heavy
   precipitation plume to spread eastward into far northern IN and
   southern Lower MI over the next several hours this morning in tandem
   with the eastward evolving low-level jet. As the low-level thermal
   profiles continue to warm with strong low-level warm advection
   occurring, a transition from snow/sleet to freezing rain and
   eventually plain rain will occur from southwest to northeast across
   this region as surface temperatures eventually rise above freezing.
   Parts of southern Lower MI should be slower to have this transition
   occur given current surface temperatures in the mid to upper 20s,
   with greater potential for freezing rain rates to exceed 0.05 inch
   per 3 hours.

   ..Gleason.. 12/30/2020

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

   ATTN...WFO...DTX...IWX...GRR...LOT...MKX...

   LAT...LON   43418453 43458324 43298280 43008281 42618318 42218376
               41858451 41498740 41438825 41578908 41938942 42378930
               42688885 43128729 43418453