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Mesoscale Discussion 124
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   Mesoscale Discussion 0124
   NWS Storm Prediction Center Norman OK
   0458 PM CST Mon Feb 17 2020

   Areas affected...Northeast Iowa...Southeast Minnesota...and
   South-Central Wisconsin

   Concerning...Heavy snow 

   Valid 172258Z - 180200Z

   SUMMARY...Moderate to occasional heavy snow should continue the
   develop this afternoon/evening, with snowfall rates approaching 1
   in/hr.

   DISCUSSION...A broad area of low-level theta-e advection has been
   persistent across northern Iowa into southern Minnesota/Wisconsin
   for much of the day. This process has resulted in a gradual warming
   of surface temperatures to near or just above freezing, perhaps 1-2
   F warmer than most model solutions were indicating. In addition to
   broad isentropic ascent, a focused region of greater mid-level
   ascent and expanding area of precipitation is occurring across
   central/north-central Iowa in association with a compact mid-level
   short-wave trough. Many areas are experiencing rain, with perhaps
   some mixed precipitation. However, where temperatures have remained
   at or near freezing, moderate to occasional heavy snow is occurring,
   mainly across parts of southwest Wisconsin and far northeast Iowa.

   Considerable uncertainty exists in the near-term placement and
   persistence of precipitation types across the region. Projections of
   observational analysis and short-term model model guidance would
   suggest snowfall potential should maximize as the focused area of
   ascent becomes colocated with low-level thermal profiles that favor
   snow. Therefore, the most likely area for moderate to heavy snow
   (with rates approaching 1 in/hr) appears confined to a narrow
   corridor from southwest Wisconsin into parts of east-central
   Wisconsin for the remainder of this afternoon into the early
   evening. 

   Farther west, across northeast Iowa and southeast/south-central
   Minnesota, warmer surface temperatures should limit snowfall
   potential. However, a period of brief moderate to heavy snow may
   occur as surface temperatures approach freezing with the advancing
   cold front.

   ..Karstens.. 02/17/2020

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

   ATTN...WFO...GRB...MKX...ARX...MPX...DMX...

   LAT...LON   43268824 42918938 42859040 42839154 43099286 43589348
               43979387 44369356 44319110 44588997 45048797 44398765
               43788786 43268824 

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Page last modified: February 18, 2020
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