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Mesoscale Discussion 23
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   Mesoscale Discussion 0023
   NWS Storm Prediction Center Norman OK
   0756 PM CST Fri Jan 06 2017

   Areas affected...portions of northeast TN...western NC...western
   into central VA and southeast WV

   Concerning...Heavy snow 

   Valid 070156Z - 070800Z

   SUMMARY...Snow will increase in intensity and coverage across the
   MCD area during the nighttime hours. One inch per hour snowfall
   rates will be common, with spotty/brief periods of 2 inch per hour
   rates not out of the question. The heaviest snowfall is expected to
   begin in the next 2-3 hours and spread southwest to northeast across
   the MCD area overnight.

   DISCUSSION...Most of the MCD area is below freezing as of 0130z, or
   soon will be. Latest RAP forecast soundings indicate a deep,
   saturated sub-freezing vertical profile. Forcing for ascent is
   expected to increase this evening as a lead shortwave impulse ahead
   of the main upper trough ejects across the central Appalachians. 
   This will result in increased frontogenetic forcing in the 700-500
   mb layer, where a somewhat shallow but sufficient dendritic growth
   zone resides. Low level cold advection will maintain a cold profile,
   while strong mid-level south/southwesterly flow continues to inject
   moisture across the region. Furthermore, north/northeast winds below
   850 mb will further support heavy snow development through
   orographic upslope processes. Heavy snowfall rates increasing to
   around 1 in/hr are expected to be underway across the region by
   03z-06z and continue through the nighttime hours. Some brief and
   spotty areas with rates near 2 in/hr, especially along the spine of
   the Appalachians, cannot be ruled out.

   ..Leitman.. 01/07/2017


   LAT...LON   35828385 37148261 37908107 38178004 38047921 37787852
               37187859 36217966 35438131 35208269 35168335 35398385

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