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Mesoscale Discussion 58
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   MESOSCALE DISCUSSION 0058
   NWS STORM PREDICTION CENTER NORMAN OK
   0320 AM CST SAT JAN 23 2016

   AREAS AFFECTED...PORTIONS OF VA/MD/DE/WV/DC METRO TO NJ/PA/NY/CT

   CONCERNING...HEAVY SNOW 

   VALID 230920Z - 231415Z

   SUMMARY...HEAVY SNOW AND INCREASINGLY STRONG NORTHEASTERLY WINDS CAN
   BE EXPECTED THROUGH MID-MORNING 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 AND SOUTHWEST CT.
   PEAK SNOW RATES ARE LIKELY TO REACH/LOCALLY EXCEED 2 IN/HR...WITH
   BLIZZARD OR NEAR-BLIZZARD CONDITIONS PARTICULARLY IN AREAS NEAR/JUST
   WEST OF THE I-95 CORRIDOR.

   DISCUSSION...WATER VAPOR IMAGERY/EVENING UPPER-AIR DATA DEPICT THE
   SLOW EASTWARD ADVANCEMENT OF A CLOSED MID-LEVEL CYCLONE OVER THE
   CENTRAL APPALACHIANS AND A STRONG/COUPLED UPPER-LEVEL JET ALONG THE
   COASTAL MID-ATLANTIC/NORTHEAST STATES. 09Z/4AM EST OBSERVATIONS
   FEATURE A STEADILY DEEPENING SURFACE LOW /988 MB/ OFF THE COAST OF
   SOUTHEAST VA WITH A NORTH/NORTHWESTWARD-EXTENDING SUBTLE INVERTED
   TROUGH THAT DELINEATES A NEAR-COASTAL CORRIDOR OF VERY STRONG
   PRESSURE FALLS OF AS MUCH AS 4-7 MB/2-HR.

   SPECIAL 06Z OBSERVED SOUNDINGS FROM WASHINGTON-DULLES AND NEW YORK
   CITY SAMPLED A SATURATED THERMODYNAMIC ENVIRONMENT CONDUCIVE FOR
   HEAVY SNOW WITH ESSENTIALLY A SATURATED DENDRITIC LAYER AROUND
   500-600 MB AND AN AGGREGATION-CONDUCIVE NEARLY ISOTHERMAL THERMAL
   LAYER BETWEEN 700-850 MB. COLLOCATION OF AMPLE MID-LEVEL
   FRONTOGENETICAL FORCING AND WEAK STATIC STABILITY...WHICH IS LARGELY
   RELATED TO THE NORTHEASTWARD-SURGING MID-LEVEL DRY SLOT PER WATER
   IMAGERY...WILL SUPPORT MULTIPLE WSW/ENE-ORIENTED INTENSE BANDS OF
   HEAVY SNOW. EMBEDDED RATES WILL REACH OR EXCEED 2 IN/HR FOR A
   MULTI-HOUR DURATION THROUGH MID-MORNING. ASIDE FROM A PERSISTENT
   NUMBER OF 1+ IN/HR RATES OBSERVED AT BALTIMORE-WASHINGTON AND
   WASHINGTON NATIONAL OVERNIGHT...METAR SNINCR OBSERVATIONS AS OF 08Z
   SUGGEST 2 IN/HR RATES ARE BEING OBSERVED AT WASHINGTON-DULLES AND
   MIDDLETOWN/HARRISBURG PA...WITH NEW YORK CITY/JFK ALSO REPORTING A 2
   IN/HR RATE AS OF 09Z.

   FURTHERMORE...REGIONAL WSR-88D VWPS ARE SAMPLING A
   NORTHWARD-SHIFTING CORRIDOR OF SIGNIFICANTLY STRENGTHENING
   EAST-NORTHEASTERLY WINDS WITHIN THE LOWEST 1-2 KM AGL...ACCENTUATED
   BY 50+ KT WINDS AROUND 1 KM PER STERLING VA-KLWX...DOVER AIR FORCE
   BASE-KDOX...AND PHILADELPHIA/MT HOLLY-KDIX WSR-88D VWP DATA. AS
   SUCH...BLIZZARD OR NEAR-BLIZZARD CONDITIONS CAN INCREASINGLY BE
   EXPECTED INTO THE MID-MORNING HOURS...PARTICULARLY IN AREAS NEAR AND
   JUST WEST /WITHIN 50 MILES OR SO/ OF INTERSTATE 95.

   ..GUYER.. 01/23/2016


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

   LAT...LON   39597440 39297504 38377691 38667853 39337885 40217832
               41247538 41407305 40847247 40527374 39597440 

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Page last modified: January 23, 2016
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