Mesoscale Discussion 1748
   NWS Storm Prediction Center Norman OK
   0956 PM CDT Wed Oct 21 2020

   Areas affected...north central South Dakota...southern North Dakota
   and west central Minnesota

   Concerning...Heavy snow 

   Valid 220256Z - 220600Z

   SUMMARY...Periods of heavy snow with rates of 1 to 2 inches per hour
   appear likely across portions of the Dakotas and western Minnesota
   tonight.

   DISCUSSION...00z observed soundings and evening water vapor imagery
   showed a mid-level shortwave trough and jet streak amplifying across
   the northern Rockies. Downstream of the trough across western South
   Dakota, radar showed a broad area of stratiform precipitation
   developing from increasing synoptic lift ahead of the trough. Model
   soundings show widespread isentropic ascent with strong low and
   mid-level warm advection across much of South Dakota. This strong
   lift will support mesoscale banding in the precip shield late this
   evening and overnight. Heavy snowfall rates of 1 to 2 inches per
   hour will be likely as these bands develop and move northeastward.
   Current model guidance suggests the most likely time frame for the
   heaviest snowfall rates will be between 6 and 9 UTC across north
   central South Dakota. With time, the heavier snow axis should shift
   northeastward and weaken as it moves into portions of southeast
   North Dakota and perhaps west central Minnesota.

   ..Lyons/Grams.. 10/22/2020

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

   ATTN...WFO...FGF...ABR...BIS...UNR...

   LAT...LON   45199812 44969963 44950097 45170170 45460201 45740218
               46020192 46310036 46529857 46419714 46269612 45889618
               45539702 45339748 45199812