ZCZC SPCSWOMCD ALL
ACUS11 KWNS 230920 
SPC MCD 230920 
NYZ000-CTZ000-NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-231415-

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

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

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

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

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