Mesoscale Discussion 1885
   NWS Storm Prediction Center Norman OK
   0217 PM CST Tue Dec 29 2020

   Areas affected...Central/eastern IA...Northern IL...Southern WI

   Concerning...Heavy snow 

   Valid 292017Z - 300015Z

   SUMMARY...Snow rates of 1 inch or greater per hour will spread
   eastward through the afternoon into the early evening. Snow may
   eventually transition to sleet and freezing rain from southern Iowa
   into northwest Illinois, with the heaviest snow rates expected just
   north of the transition zone.

   DISCUSSION...At 20Z, moderate to occasionally heavy winter
   precipitation is spreading eastward across IA into portions of
   southwest WI and northwest IL. Precipitation is primarily snow
   across IA, though a transition to sleet/freezing rain has been noted
   across far southwest/south-central IA, based on surface observations
   and radar. Low-level warm advection will continue to support strong
   ascent and also result in a gradual northeastward shift of the
   snow/sleet/freezing rain transition zone with time. 

   Increasing frontogenesis within the 900-700 mb layer will continue
   to support occasionally heavy precipitation rates, and possibly some
   organized snow bands where rates may approach 2 inches/hour at
   times. The heaviest snow rates are expected just north of the snow
   to sleet/freezing rain transition zone, with several hours of
   moderate-to-heavy snow possible from central/east-central IA into
   northwest IL and far southwest WI by early evening. The southern
   portion of the MCD area will likely transition to sleet/freezing
   rain by 00Z.

   ..Dean.. 12/29/2020

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

   ATTN...WFO...LOT...ILX...MKX...DVN...ARX...DMX...

   LAT...LON   41739401 42239390 42489350 42789235 42919153 42969064
               42978986 42778905 42238859 41758872 41448916 41288956
               41168983 41039060 40979115 41019208 41149341 41369396
               41739401