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Mesoscale Discussion 62
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   Mesoscale Discussion 0062
   NWS Storm Prediction Center Norman OK
   0308 AM CST Fri Feb 09 2018

   Areas affected...Portions of far eastern Iowa to southern Michigan

   Concerning...Heavy snow 

   Valid 090908Z - 091515Z

   SUMMARY...Moderate to locally heavy snow, with rates up to one inch
   per hour, will continue expanding eastward this morning.

   DISCUSSION...On the nose of stronger 850-700mb warm advection and
   related isentropic ascent, moderate snowfall has advanced eastward
   into portions of northern Indiana and southern Michigan early this
   morning. Forecast soundings depict ascent through a dendritic-growth
   layer several thousand feet deep. Therefore, while upward vertical
   motion is not particularly robust, relatively efficient crystal
   growth should compensate somewhat, yielding rates around 0.5-1 inch
   per hour this morning.

   Farther west into northern Illinois, the strongest upward motion
   related to warm advection has generally remained at temperature
   levels too warm for dendritic growth, limiting snowfall rates.
   However, likely related to increasing 700-mb confluence and
   associated frontogenetic circulations, a narrow band of higher
   reflectivity (suggesting an increase in snow aggregation) has
   organized over northern Illinois. Ascent associated with this band
   exists at colder temperatures, in turn favoring more efficient
   crystal production. Supporting this notion, KDVN/Quad Cities 88D
   data highlight subtle enhancements in KDP (0.2-0.4 deg/km) around
   11-13K ft AGL, which is consistent with an increase in
   planar/dendritic crystal growth. This narrow band will slowly shift
   east this morning, but will likely be positioned over northern
   Illinois over the next several hours, potentially impacting the
   morning rush hour with localized snowfall rates up to one inch per
   hour.

   ..Picca.. 02/09/2018

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

   ATTN...WFO...DTX...IWX...GRR...LOT...MKX...DVN...

   LAT...LON   41619151 42249045 42618839 42838563 42768449 42678370
               42238329 41918348 41728408 41398589 41428878 41459061
               41389115 41399149 41619151 

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Page last modified: February 09, 2018
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