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Mesoscale Discussion 59
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   MESOSCALE DISCUSSION 0059
   NWS STORM PREDICTION CENTER NORMAN OK
   0751 AM CST SAT JAN 23 2016

   AREAS AFFECTED...NORTHERN VA/DC METRO AND MD/DE/WV TO NJ/PA AND
   SOUTHERN NY/CT

   CONCERNING...HEAVY SNOW 

   VALID 231351Z - 231745Z

   SUMMARY...HEAVY SNOW WILL PERSIST THROUGH MIDDAY FROM NORTHERN VA/DE
   AND DC METRO/WV EASTERN PANHANDLE/INTERIOR MD TO NJ AND
   SOUTHERN/EASTERN PA TO FAR SOUTHERN NY INCLUDING THE NYC METRO/LONG
   ISLAND...WHILE INCREASING INTO SOUTHERN CT. PEAK SNOW RATES WITHIN
   THIS CORRIDOR WILL LOCALLY EXCEED 2 IN/HR...WITH BLIZZARD OR
   NEAR-BLIZZARD CONDITIONS CONTINUING PARTICULARLY IN AREAS NEAR/JUST
   WEST OF THE I-95 CORRIDOR.

   DISCUSSION...WATER VAPOR IMAGERY/UPPER-AIR DATA FEATURE THE SLOW
   EASTWARD ADVANCEMENT OF A CLOSED MID-LEVEL CYCLONE OVER/JUST EAST OF
   THE CENTRAL APPALACHIANS WITH A STRONG/COUPLED UPPER-LEVEL JET
   FOCUSED OVER THE COASTAL NORTHEAST STATES. 13Z/8AM EST OBSERVATIONS
   DEPICT AN OFFSHORE SURFACE LOW /APPROX 988 MB/ OFF THE COAST OF
   SOUTHEAST VA/DELMARVA WITH A PERSISTENT NORTH/NORTHWESTWARD-
   EXTENDING NEAR-COASTAL CORRIDOR OF EARLY-MORNING PRESSURE FALLS OF
   AS MUCH AS 2-3 MB/2-HR OFF NJ INTO NEAR-COASTAL SOUTHERN NEW
   ENGLAND.

   SIMILAR TO 06Z...RECENT 12Z OBSERVED SOUNDINGS FROM
   WASHINGTON-DULLES AND NEW YORK CITY SAMPLED A SATURATED
   THERMODYNAMIC ENVIRONMENT CONDUCIVE FOR HEAVY SNOW WITH A DENDRITIC
   LAYER AROUND 500-600 MB AND AN AGGREGATION-CONDUCIVE NEARLY
   ISOTHERMAL LAYER BETWEEN 700-900 MB. RELATED TO THE
   NORTHEASTWARD-ADVANCING DRY SLOT PER WATER VAPOR IMAGERY...THE 12Z
   OBSERVED SOUNDING FROM WALLOPS ISLAND VA SAMPLED A RELATIVELY STEEP
   LAPSE RATE/WEAK ELEVATED CAPE BETWEEN 850-500 MB...WHICH RELATES TO
   THE NEAR-COASTAL WEAK UPRIGHT INSTABILITY AND WEAK STATIC STABILITY
   THAT EXISTS ACROSS A BROADER PART OF THE REGION. SINCE AROUND
   09Z...OCCASIONAL CLOUD-TO-GROUND/IN-CLOUD LIGHTNING HAS BEEN NOTED
   FROM AROUND THE DC METRO/BALTIMORE VICINITY INTO SOUTHEAST PA...AND
   BRIEF/LOCALIZED BOUTS OF THUNDERSNOW WILL REMAIN A POSSIBILITY.

   BASED ON RECENT MANUALLY AUGMENTED SNINCR OBSERVATIONS...2 IN/HR
   SNOW RATES CONTINUE TO BE NOTED AT NEW YORK JFK...MIDDLETOWN/
   HARRISBURG PA...NEWARK NJ AND NEW YORK LA GUARDIA AS OF 13Z/8AM
   EST...WITH A 3 IN/HR RATE NOTED AT ISLIP/MACARTHUR NY.
   BLIZZARD-CALIBER WIND GUSTS ARE ALSO NOTED AT THE NEW YORK CITY/LONG
   ISLAND VICINITY OBSERVATIONS...HIGHLIGHTED BY A 41 KT GUST AS 1235Z
   AT NEW YORK LA GUARDIA. REGIONAL WSR-88D VWPS CONTINUE TO SAMPLE A
   NORTHWARD-SHIFTING CORRIDOR OF VERY STRONG EAST-NORTHEASTERLY WINDS
   WITHIN THE LOWEST 1-2 KM AGL...ACCENTUATED BY 50-65 KT WINDS AROUND
   1 KM PER STERLING VA-KLWX...DOVER AIR FORCE BASE-KDOX...
   PHILADELPHIA/MT HOLLY-KDIX...AND UPTON NY WSR-88D VWP DATA. 

   PER THE AFOREMENTIONED OBSERVATIONS AND SHORT-TERM RAP
   GUIDANCE...THE COLLOCATION OF AMPLE MID-LEVEL FRONTOGENETICAL
   FORCING AND WEAK STATIC STABILITY WILL CONTINUE TO SUPPORT MULTIPLE
   WSW/ENE-ORIENTED INTENSE BANDS OF HEAVY SNOW. EMBEDDED RATES ARE
   LIKELY TO CONTINUE TO EXCEED 2 IN/HR FOR A MULTI-HOUR DURATION
   THROUGH MIDDAY/EARLY AFTERNOON. BLIZZARD OR NEAR-BLIZZARD CONDITIONS
   WILL ALSO CONTINUE PARTICULARLY FOR AREAS NEAR AND JUST WEST /WITHIN
   50 MILES OR SO/ OF INTERSTATE 95 INCLUDING THE NEW YORK CITY
   VICINITY.

   ..GUYER.. 01/23/2016


   ATTN...WFO...OKX...PHI...BGM...CTP...LWX...

   LAT...LON   39777439 39677547 38547766 38647837 39167877 40197787
               41397425 41347237 40877254 40557369 39777439 

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