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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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