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Mesoscale Discussion 124
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   MESOSCALE DISCUSSION 0124
   NWS STORM PREDICTION CENTER NORMAN OK
   0658 AM CST THU MAR 05 2015

   AREAS AFFECTED...WV AND WESTERN/NORTHERN VA TO DC METRO/MD/SOUTHEAST
   PA/NJ/DE

   CONCERNING...HEAVY SNOW 

   VALID 051258Z - 051800Z

   SUMMARY...INCREASINGLY HEAVY SNOW IS EXPECTED THROUGH LATE
   MORNING/AFTERNOON WITH HEAVIER SNOWFALL RATES EXCEEDING 1
   IN/HR...PARTICULARLY INCLUDING A CORRIDOR ACROSS SOUTHERN/EASTERN
   WV...WESTERN/NORTHERN VA...FAR SOUTHEAST PA...THE DC METRO...NJ/MD
   AND NORTHERN DE.

   DISCUSSION...PRECIPITATION RATES WILL INCREASE ACROSS MUCH OF THE
   CENTRAL APPALACHIANS AND MID-ATLANTIC STATES/DELMARVA VICINITY BY
   MID/LATE MORNING AND AFTERNOON IN ASSOCIATION WITH AN AMPLIFYING
   UPSTREAM SHORTWAVE TROUGH AND AMPLE ISENTROPIC LIFT/FRONTOGENETICAL
   FORCING. NEAR-SURFACE SUB-FREEZING AIR CONTINUES TO STEADILY
   PROGRESS SOUTHEASTWARD EARLY THIS MORNING...WITH THE SURFACE
   WET-BULB 32F ISOLINE EXTENDING ACROSS FAR WESTERN/NORTHERN VA...NEAR
   THE DC METRO AREA...TO NEAR PHILADELPHIA/CENTRAL NJ AS OF 12Z.  

   AS COLDER AIR IN THE LOW LEVELS CONTINUES TO TRANSITION
   SOUTHEASTWARD...INCREASING FORCING FOR ASCENT COINCIDENT WITH A
   FAVORABLE ELEVATED THERMODYNAMIC PROFILE FOR DENDRITIC GROWTH SHOULD
   CONTRIBUTE TO A SCENARIO FAVORABLE FOR INCREASINGLY HEAVY
   SNOW...WITH SOME SLEET ALSO INITIALLY POSSIBLE. SNOWFALL RATES ARE
   LIKELY TO LOCALLY EXCEED 1 IN/HR WITHIN THIS CORRIDOR. THE 12Z
   OBSERVED SOUNDING FROM WASHINGTON-DULLES SUBSTANTIATES THIS NOTION
   WITH CONSIDERABLE COOLING HAVING OCCURRED BELOW 700 MB OVER THE PAST
   12-HOURS...WITH ONLY A NEGLIGIBLE ABOVE-FREEZING ELEVATED LAYER
   /AROUND 0.5C/ REMAINING AT 850 MB AS OF 12Z. OF NOTE RELATED TO
   NUMERICAL GUIDANCE...THIS OBSERVED ELEVATED WARM LAYER AT KIAD WAS
   AS MUCH AS 2-3C COLDER /750-700 MB/ THAN THE 06Z NAM POINT FORECAST
   BUT SIMILAR TO THE 06Z GFS FORECAST PROFILE.

   ..GUYER.. 03/05/2015


   ATTN...WFO...PHI...CTP...LWX...RNK...PBZ...RLX...

   LAT...LON   37098013 37548142 38458163 40137779 40467420 39547430
               39267498 38447776 37098013 

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Page last modified: March 05, 2015
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