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Mesoscale Discussion 99
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   MESOSCALE DISCUSSION 0099
   NWS STORM PREDICTION CENTER NORMAN OK
   0700 AM CST THU FEB 13 2014

   AREAS AFFECTED...MID-ATLANTIC/NORTHEAST STATES

   CONCERNING...HEAVY SNOW 

   VALID 131300Z - 131800Z

   SUMMARY...MODERATE TO HEAVY SNOW...WITH SNOW RATES OF 1-2 IN/HR
   LIKELY...WILL CONTINUE TO DEVELOP NORTH-NORTHEASTWARD ACROSS THE
   COASTAL NORTHEASTERN STATES THIS MORNING. SNOW WILL INTENSIFY
   ESPECIALLY ACROSS SOUTHERN NEW YORK/NYC METRO INTO SOUTHERN NEW
   ENGLAND THROUGH LATE MORNING/EARLY AFTERNOON. A TRANSITIONAL MIX OF
   PRECIPITATION WILL OCCUR IN COASTAL PLAIN AREAS THROUGH THE
   AFTERNOON...ESPECIALLY IN AREAS WITHIN 50-75 MILES OF THE ATLANTIC.

   DISCUSSION...A SHORTWAVE TROUGH CONTINUES TO SHIFT
   EAST-NORTHEASTWARD TO THE EAST OF THE CENTRAL/SOUTHERN APPALACHIANS
   EARLY THIS MORNING...WITH A BAROCLINIC LEAF STRUCTURE READILY
   EVIDENT OVER THE EASTERN SEABOARD IN IR/WV SATELLITE IMAGERY. A
   DEEPENING SURFACE LOW IS CENTERED NEAR THE NC OUTER BANKS AS OF
   12Z...WITH STRONG WARM/MOIST ADVECTION OCCURRING NEAR/JUST ABOVE THE
   SURFACE IN COASTAL AREAS AS PER WSR-88D VWP/12Z UPPER AIR DATA.

   THIS SCENARIO WILL LEAD TO A GENERAL NORTHEASTWARD TRANSITION OF
   CONSIDERABLE UVV FROM THE DELMARVA VICINITY TO SOUTHERN NEW ENGLAND
   BY MIDDAY. AS PER 12Z OBSERVED REGIONAL SOUNDINGS...SNOW WILL BE THE
   DOMINANT PRECIPITATION TYPE ESPECIALLY FOR INLAND AREAS...WITH
   SATURATED MID-LEVEL DENDRITIC LAYERS /SUCH AS 12Z ALBANY AND
   NYC-LONG ISLAND SOUNDINGS/ CONDUCIVE FOR BOUTS OF MODERATE TO HEAVY
   SNOW FROM FAR EASTERN PA/NORTHERN NJ INTO SOUTHERN NY/SOUTHERN NEW
   ENGLAND. 

   IN NEAR-COASTAL AREAS...ROUGHLY WITHIN 50-75 MILES OF THE
   ATLANTIC...A TRANSITIONAL MIX OF PRECIPITATION CAN BE EXPECTED
   THROUGH THE AFTERNOON...ESPECIALLY GIVEN THAT THE LONG ISLAND 12Z
   OBSERVED SOUNDING WAS ONLY MARGINALLY SUB-0C BELOW 850 MB/1.3 KM
   AGL. THIS NEAR-COASTAL TRANSITIONAL MIX WILL BE DRIVEN BY PERSISTENT
   LOW-LEVEL WARM ADVECTION QUASI-FOCUSED ACROSS THE NYC METRO
   VICINITY/FAR SOUTHERN NY INTO SOUTHERN NEW ENGLAND.

   ..GUYER.. 02/13/2014


   ATTN...WFO...GYX...BOX...OKX...ALY...PHI...BGM...CTP...LWX...

   LAT...LON   39557777 40977588 42297520 42987285 43427152 43787081
               43647024 42747048 42117070 41637128 40187394 39617595
               38757693 39027793 39557777 

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Page last modified: February 13, 2014
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