ZCZC SPCSWOMCD ALL ACUS11 KWNS 231351 SPC MCD 231351 CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-231745- 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 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...OKX...PHI...BGM...CTP...LWX... LAT...LON 39777439 39677547 38547766 38647837 39167877 40197787 41397425 41347237 40877254 40557369 39777439 NNNN