Mesoscale Discussion 1974
   NWS Storm Prediction Center Norman OK
   0949 PM CST Thu Dec 09 2021

   Areas affected...Parts of eastern Wyoming...southern South
   Dakota...and northern Nebraska

   Concerning...Heavy snow 

   Valid 100349Z - 100845Z

   SUMMARY...Heavy snow with rates of 1-1.5 in/hr are expected to
   develop tonight from eastern Wyoming and spread east-northeastward
   across southern South Dakota and northern Nebraska.

   DISCUSSION...A band of strong low/mid-level warm air advection
   preceding a deepening low-pressure system over eastern Colorado will
   gradually overspread portions of the central Great Plains during the
   overnight hours. As the increasing ascent moves over deepening
   subfreezing layers per the latest RAP and NAM forecast soundings,
   chances for heavy snowfall will gradually increase. A band of
   moderate snow is already in progress along the Nebraska/South Dakota
   border, which is contributing to low/mid-level saturation.

   The heavy snow will most likely develop across parts of eastern
   Wyoming and northwestern Nebraska, before shifting north/east across
   southern South Dakota and north-central Nebraska in the 06-09Z
   timeframe as suggested by the latest high-resolution model guidance.
   Latest forecast soundings suggest deep/saturated dendritic growth
   zones colocated with strong ascent aided by the plume of warm air
   advection. These factors, combined with a developing frontogenetic
   circulation will support snowfall rates of 1-1.5 in/hr.

   ..Weinman/Squitieri.. 12/10/2021

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

   ATTN...WFO...FSD...LBF...UNR...CYS...

   LAT...LON   41890447 42230446 42770444 43100412 43290334 43330163
               43309973 43219902 42919907 42469902 42239928 42200009
               42210073 42230157 42230266 42170318 42080343 41890368
               41810398 41820429 41890447