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Mesoscale Discussion 22
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MD 22 graphic

   Mesoscale Discussion 0022
   NWS Storm Prediction Center Norman OK
   0513 PM CST Fri Jan 06 2017

   Areas affected...northern GA into far northern SC

   Concerning...Winter mixed precipitation 

   Valid 062313Z - 070515Z

   SUMMARY...Precipitation is expected to transition to snow across far
   northern GA and adjacent portions of northern SC over the next
   couple of hours as surface temperatures quickly cool. A bit further
   south, a wintry mix is expected with freezing rain and sleet,
   possibly mixed with snow. This wintry mix will include the greater
   Atlanta metro area into the nighttime hours.

   DISCUSSION...Surface temperatures across the MCD area ranged from
   around 30 to 35 degrees F in GA with 35 to 40 degree temperatures
   being reported in adjacent portions of northern SC as of 23z.
   Looking at the surface wet-bulb temperatures, many areas across far
   northern GA should already be seeing a transition to snow. This is
   further supported by radar observations from the KFFC WSR-88D, in
   conjunction with latest RAP forecast soundings, indicating any
   melting layer aloft is quickly eroding across the far northern MCD
   area. Snowfall rates should generally be less than 1 in/hr but some
   spotty/brief periods of heavy snow is possible into the nighttime
   hours. 

   Further south, along a line roughly extending from Polk County GA
   east-northeast to Oconee County SC, southward to Heard County GA to
   Hart County, GA /red shaded area in the MCD graphic/...mixed
   precipitation types are expected. A 21z RAOB from FFC showed a
   classic freezing rain sounding with an elevated warm nose around 850
   mb of 5.5 deg C. Cold low level advection in conjunction with
   wet-bulb temperatures approaching freezing over the next 1-2 hours,
   should result in a transition toward sleet and freezing rain...and
   possibly some snow mixed in later tonight when the elevated warm
   layer erodes /probably not until after 06z/. In fact, an mPING
   report was submitted in Cobb County GA at 2250z indicating freezing
   rain. This ground truth further supports a transition from rain to
   mixed wintry precip types very soon across the southern half of the
   MCD area.  Precipitation rates generally should be light, with
   periods of moderate to heavy freezing rain at times through this
   evening.

   ..Leitman.. 01/06/2017


   ATTN...WFO...GSP...MRX...FFC...BMX...HUN...

   LAT...LON   33548538 34138558 34718564 34998527 35088391 35098334
               34948300 34668297 34508294 33968354 33368471 33318525
               33548538 

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Page last modified: January 07, 2017
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