Mesoscale Discussion 0392
   NWS Storm Prediction Center Norman OK
   0543 PM CDT Thu Apr 16 2020

   Areas affected...Southeast Nebraska...southern Iowa... northern
   Missouri...and far west central Illinois

   Concerning...Heavy snow 

   Valid 162243Z - 170245Z

   SUMMARY...A band of heavy snow with snow rates between 1-2 in/hr
   will likely continue across far southeast NE, southern IA, northern
   MO, and far west central IL through the evening hours.

   DISCUSSION...Recent ASOS observations from eastern NE report heavy
   snow with visibility at or below one mile at times. These reports,
   in conjunction with snowfall reports from the past few hours of 1-2
   inches of snow accumulation, suggest that the snow band in place
   across east/southeast NE, southern IA, and northern MO continues to
   produce areas of snow rates between 1-2 in/hour. Recent radar trends
   show increasing organization of this band, which is largely being
   driven by strengthening 850-700 mb frontogenesis and strong
   isentropic ascent over the region ahead of a mid level shortwave
   trough. Low to mid level cold advection across the central High
   Plains through the evening hours will hinder rapid eastward
   translation of the shortwave trough and may act to increase mid
   level flow via thermal wind responses. As such, the forcing
   mechanisms of this snow band will likely continue through the
   evening hours as the feature slowly propagates to the east within
   the mean flow. 

   Given the strength of the mesoscale forcing for ascent and radar
   presentation, snowfall rates of 1-2 in/hour should still continue at
   least for the next several hours. There is some uncertainty
   regarding the eastward extent of the heavy snowfall potential across
   southeast IA/west central IL where surface wet bulb temperatures are
   current at or just above freezing amid relatively high (5-10 F)
   surface dewpoint depressions. This implies that snowfall rates may
   be reduced due to low level evaporation prior to full column
   saturation.

   ..Moore/Goss.. 04/16/2020

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

   ATTN...WFO...ILX...LSX...DVN...DMX...EAX...OAX...

   LAT...LON   41529621 41629461 41479208 41159072 40639050 40189079
               40019149 40029234 40139370 40209544 40409641 40849699
               41279688 41529621