Mesoscale Discussion 1868
   NWS Storm Prediction Center Norman OK
   0515 PM CST Wed Dec 23 2020

   Areas affected...Portions of far northern IA...MN...western/northern
   WI...and extreme western Upper MI

   Concerning...Blizzard 

   Valid 232315Z - 240515Z

   SUMMARY...Heavy snow, with rates of 1-2 inches per hour, is expected
   to continue this evening while gradually shifting eastward. Blizzard
   conditions should continue for a few more hours across parts of
   northern IA into MN.

   DISCUSSION...A deep surface low over northern WI at 23Z will
   continue to track northeastward into the U.P. of MI this evening
   while very slowly weakening. A tight surface pressure gradient on
   the north and west side of this low is resulting in rather
   strong/gusty low-level flow, with multiple observations showing
   sustained north-northwesterly winds of 30-40 mph in parts of
   northern IA and southern/central/eastern MN. Higher gusts of 45-60
   mph have also been observed recently, which combined with the
   ongoing heavy snow is resulting in greatly reduced visibilities and
   blizzard conditions across these areas.

   Current expectations are for these strong low-level winds to very
   gradually weaken this evening as the surface pressure gradient
   relaxes. This should lead to a slow reduction in blizzard conditions
   through the evening. Regardless, an ongoing band of heavy snow being
   driven by low to mid-level frontogenetic forcing on the backside of
   an upper trough will continue to produce snowfall rates of 1-2
   inches per hour through at least 03Z as it develops slowly eastward
   across parts of eastern/northern MN, western WI, and the extreme
   western portions of the U.P. of MI. By late this evening, this heavy
   snow band should begin to diminish in intensity as the large-scale
   forcing weakens with the upper trough continuing to progress
   eastward.

   ..Gleason.. 12/23/2020

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

   ATTN...WFO...MQT...GRB...DLH...ARX...MPX...DMX...

   LAT...LON   44069244 43479333 43119408 43129446 43729470 44319475
               45579404 47439270 47939210 48189160 48299084 48169012
               48028949 47398934 46648943 46088989 45539085 44069244