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Mesoscale Discussion 56
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   Mesoscale Discussion 0056
   NWS Storm Prediction Center Norman OK
   0428 AM CST Wed Feb 07 2018

   Areas affected...eastern WV...much of PA...northeast OH...and
   western into central NY

   Concerning...Winter mixed precipitation 

   Valid 071028Z - 071530Z

   SUMMARY...Heavier rates of winter precipitation are forecast across
   the discussion area.  One inch per hour snowfall rates are expected
   from northeast OH through northern PA and into NY.  Freezing rain
   rates at or above 0.05 inch per hour are expected from eastern WV
   into south-central PA.

   DISCUSSION...Radar mosaic shows an extensive precipitation shield
   from the TN Valley northeast through the upper OH Valley early this
   morning.  Surface analysis indicates temperatures are below freezing
   from near the OH River northeast through southwest PA, eastern WV,
   and east towards the north part of the Chesapeake Bay.  88D VAD data
   show strong and veering flow with height --implying strong low-level
   warm-air-advection process-- concurrent with the northeastward
   movement of the precipitation shield and saturation of the low-level
   profile with time over PA, and in time, over NY.

   Forecast soundings of the area suggest the thermal profile will
   support snow from northeast OH through northern portions of PA and
   into NY.  Generally steady rates around 1 inch per hour are forecast
   for several hours on the northern portion of the evolving
   precipitation plume.  Farther south, a warm layer above a
   sub-freezing near-surface layer will favor mixed precipitation,
   primarily in the form of freezing rain.  Rates at or above 0.05 inch
   per 3 hours are expected per model guidance as the profile continues
   to moisten.  During the mid-late morning hours, a gradual transition
   of freezing rain to rain is expected to occur from south to north as
   surface temperatures warm above freezing.

   ..Smith.. 02/07/2018

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

   ATTN...WFO...ALY...PHI...BGM...BUF...CTP...LWX...PBZ...CLE...

   LAT...LON   42267468 40357571 39007923 40298007 40868225 41628180
               43677578 43527430 42267468 

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Page last modified: February 07, 2018
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