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Mesoscale Discussion 25
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   Mesoscale Discussion 0025
   NWS Storm Prediction Center Norman OK
   0218 AM CST Sat Jan 07 2017

   Areas affected...Western/central NC...southern VA

   Concerning...Winter mixed precipitation 

   Valid 070818Z - 071315Z

   SUMMARY...A mix of winter precipitation is expected across portions
   of western/central NC and southern VA over the next several hours.
   Snowfall rates from one to two inches per hour and freezing rain
   rates in excess of 0.02 inch per hour are possible across portions
   of the region.

   DISCUSSION...Recent regional radar imagery and surface observations
   indicate a complex mix of precipitation types, as well as heavy
   snowfall, across portions of western and central NC and southern VA.
   Across the higher terrain of western NC and far southwestern VA,
   persistent large-scale forcing for ascent associated with the
   approaching shortwave trough coupled with modest upslope flow
   resulting from north/northeasterly flow below 850 mb will support
   continued heavy snowfall for the next few hours, while gradually
   tapering off from west to east. Snowfall rates around 1 inch per
   hour are possible.

   Farther south and east (from south-central NC northeastward in far
   northeastern NC and far southeastern VA), a transition zone from
   snow to a mix of snow, sleet, and freezing rain, and then rain will
   continue to drift slowly northward. As the upper system matures,
   strengthening low-level winds will increase warm-air advection into
   the region, with the resulting increase in ascent supporting the
   possibility of moderate freezing rain rates (above 0.02 - 0.03 inch
   an hour). These moderate rates are confirmed by observations at RWI
   and RDU, which have recently reported 0.06 and 0.02 inches of ice
   accretion, respectively, in the last hour.

   From north-central NC northeastward to southern portions of the
   Delmarva peninsula, snowfall rates are expected to gradually
   increase as the low-level winds increase in response to the maturing
   upper system. Subsequent increase in warm-air advection will support
   strong mesoscale forcing for ascent, with rates near 2 inches per
   hour possible in the 9Z to 12Z timeframe, particularly across
   southeastern VA and the southern Delmarva peninsula.

   ..Mosier.. 01/07/2017


   LAT...LON   36298179 37158067 37667901 37967744 37757572 36887552
               35977647 35347919 34928093 34968242 36298179 

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