Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251429 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 929 AM EST TUE NOV 25 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD INTO THE REGION TODAY FROM THE SOUTHWEST. THEN, A STORM WILL DEVELOP NEAR THE SOUTHEASTERN UNITED STATES COAST TONIGHT AND STRENGTHEN AS IT MOVES NORTHEAST PASSING EAST OF CAPE COD EARLY THANKSGIVING MORNING. A LARGE AREA OF HIGH PRESSURE WILL THEN BUILD IN FROM THE CENTRAL PART OF THE NATION FOR FRIDAY THROUGH SATURDAY BEFORE IT MOVES OFFSHORE ON SUNDAY. A COLD FRONT ASSOCIATED WITH AN AREA OF LOW PRESSURE IN EASTERN CANADA WILL CROSS THE REGION SUNDAY OR MONDAY. && .NEAR TERM /THROUGH TONIGHT/... QUIET WEATHER... FOR THOSE IN THE WATCH AREA...GET YOUR WORK/ERRANDS DONE TODAY. TODAY...LOTS OF HIGH CLOUDS WITH WEAK HIGH PRESSURE CENTRAL APPS. CIRRUS ON THE RRQ OF 250 JET AXISED NE-SW WEST OF THE APPS WITH 210 SPEED MAX`S MODELED ST LAWR VALLEY. WET BULBS START LOWERING IN CAA WITH WESTERLY WIND GUST TO 20 KT. NO CHANGE AT THIS TIME TO FORECAST. TONIGHT...RAIN DEVELOPS FROM SOUTH SOUTHWEST TO NORTH NORTHEAST AFTER MIDNIGHT AS LOW PRESSURE HEADS NEWD FOR THE NC COAST. NO CHANGE AT THIS TIME TO ANY GRIDS. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... **HIGH VISIBILITY HIGH IMPACT SNOW EVENT FOR ELEVATIONS OF E PA AND NW NJ 9A-9P AND LIKELY A DEVELOPING IMPACT EVENT TO NEAR SEA LEVEL JUST NW OF I95 WED AFTN/EVE** 930 AM ESTF: FIRST WARNING ISSUANCE NOW AS STERLING UPGRADES AND MOVES FASTER AS WELL. WE WONT CHANGE ANY SNOW TOTAL GRIDS AT THIS TIME. WE CONTINUE MORE UNCERTAINTY SE OF THE WARNING BUT NAM PROFILE IS COLDER AT PHL WHICH COULD MEAN 3 TO 6 INCHES THERE EVEN DURING THE DAY. POWER OUTAGES A CONCERN I95. SUGGEST TRAVEL INTO E PA AND NW NJ COMPLETED NO LATER THAN 7 AM WEDNESDAY, OR WAIT TIL AFTER 7 PM WEDNESDAY NIGHT. ITS THAT 12 HOUR WINDOW THAT IS GOING TO BECOME A SIGNIFICANT TRAVEL PROBLEM, ESPECIALLY THE HILLY AREAS. ITS UNUSUAL TO FCST HEAVY WET SNOW IN A 1000-500MB 543-546 THICKNESS WITHOUT A BIG SFC HIGH TO THE NORTH BUT THIS IS A SITN THAT I THINK IT WILL OCCUR, ESPECIALLY ELEVATIONS FOR REASONS BELOW. BARRING THE OFF LINE CHATTER OF AN IGW WHICH I DONT THINK WILL OCCUR IN THIS SITN BECAUSE I THINK WE`RE LACKING A COUPLE OF ELEMENTS INCLUDING SHORTENING WAVE LENGTH, THE SREF AND ECMWF MIX I THINK HAVE BEEN STEADFAST ON ADVERTISING THIS EVENT. IF AN IGW WERE TO OCCUR I DONT THINK TODAYS SCIENCE CAN BE SURE THIS FAR IN ADVANCE, BUT PLEASE CORRECT ME. SUSPECT WE WONT KNOW TIL WED MORNING. SO...AN INTENSIFYING 190M 12HR NEWD MOVING 500MB HFC COMBINES WITH ISALLOBARIC GRADIENT TO PULL 0-6KM 1C OR LESS WBZ SEWD TO NEAR I95 DURING THE AFTN. ELEVATIONS CHANGE PTYPE FIRST. PIVA AND COMMA HEAD SUGGEST SOME BANDING POTENTIAL VCNTY KRDG TO KMPO DURING THE DAY. THE MAX UVM RIGHT NOW IS TENDING TO SHOW UP BELOW THE IDEAL DENDRITIC GROWTH ZONE IN THE MULTI MODEL PROFILES BUT THAT CAN CHANGE. A RECORD DAILY SNOWFALL IS FORECAST FOR ALLENTOWN PA (A VULNERABLE RECORD). MODEL GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT OVERALL ON THE EVOLUTION OF A STORM WHICH WILL DEVELOP OFF THE SERN CONUS CST ON WED THEN TRACK NEWD DURG THE DAY ON WED. HOWEVER, WHILE THERE IS GOOD AGREEMENT ON THE SYNOPTIC FEATURES, THERE REMAINS SOME DISAGREEMENT ON THE THERMAL PROFILES AND SOME THE FINER DETAILS, WHICH COULD PROVE IMPORTANT AS THE EVENT PLAYS OUT. IT CONTINUES TO APPEAR AS THE AREAS N AND W OF PHILADELPHIA HAVE THE BEST SHOT OF SEEING SUBSTANTIAL ELEVATION RELATED SNOW, WHICH WILL IMPACT TRAVEL SIGNIFICANTLY. SRN AND ERN AREAS SE OF THE I95 CORRIDOR WILL LIKELY STAY ALL OR MOSTLY RAIN, SOME OF WHICH COULD BE HEAVY AT TIMES. THE POTENTIAL FOR SOME PONDING OF RAIN ON ROADWAYS AND POOR DRAINAGE AREAS IS POSSIBLE IN THESE LOCATIONS. THE BIGGEST QUESTION MARK IS WHAT HAPPENS ALONG THE I-95 CORRIDOR. TEMPS LOOK MARGINAL. CERTAINLY ABOVE FREEZING AT THE START OF THE EVENT, COOLING DURING IT, BUT HOW MUCH. MODEL GUID VARIES AS TO WHAT DEW POINTS WILL BE, AND HENCE WHEN THE PRECIP START WHERE THE WET BULB ZERO WILL BE. A DEGREE OR TWO CAN MAKE A WORLD OF DIFFERENCE HERE. ADDITIONALLY, IT WAS QUITE WARM ON MONDAY AND WILL BE FAIRLY WARM TODAY SO THE GROUND HAS IS WARM WHICH MAY NEGATE SOME ACCUMS, ESPECIALLY AT THE ONSET ON ROADWAYS ETC, UNLESS THE SNOW COMES DOWN HEAVY. SO, ULTIMATELY IT REMAINS TO BE SEEN WHAT WILL WIN OUT IN THIS AREA. THERE IS ALSO THE POTENTIAL FROM THE I-95 CORRIDOR N AND W FOR SOME MESOSCALE BANDING WHICH COULD INCREASE ANY SNOWFALL RATES, BUT THIS IS OFTEN DIFFICULT TO PREDICT MORE THAN A FEW HOURS IN ADVANCE, AND AMOUNTS CAN VARY WIDELY BETWEEN THOSE AREAS UNDER A BAND AND THOSE WHICH ARE NOT. THE MOST LIKELY PLACES TO REACH HEADLINE CRITERIA WOULD BE FROM BERKS COUNTY NEWD THROUGH THE LEHIGH VALLEY INTO NW NJ. PRECIPITATION ..SAID PRECIPITATION.. SINCE SOME AREAS THAT SNOW FOR A TIME WED AFTN MAY END AS SPRINKLES WED EVENING, ESPECIALLY I95 REGION. && .LONG TERM /THURSDAY THROUGH MONDAY/... LOW PRES WILL MOVE ACRS ERN CANADA ON SUN AND ITS ASSOCD CDFNT WILL CROSS THE REGION SUN NIGHT OR ERLY MON, BRINGING ANOTHER SHOT OF PRECIP, MAINLY IN THE FORM OF RAIN. GUID IS NOW SUGGESTING THAT A WAVE COULD FORM ON THIS FRONT ON MON, WHICH WOULD LINGER PRECIP CHCS. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS SHOULD CONTINUE THROUGH AT LEAST 00Z. THROUGH THIS TIME, EXPECT ONLY HIGH CLOUDS WITH CEILINGS ABOVE 10000 FT AGL. WESTERLY WINDS COULD GUST TO 20KT AT TIMES THROUGH THE DAY. AFTER 00Z...CEILINGS SLOWLY START TO LOWER. MOST TAF SITES FROM THE DELAWARE RIVER VALLEY AND FURTHER WEST (KPHL, KILG, KPNE, KTTN, KABE, AND KRDG) WILL LIKELY SEE CEILINGS STAY IN THE VFR RANGE THROUGH 12Z. AT KMIV AND KACY HOWEVER, THEY COULD SEE MVFR CEILINGS MOVE IN BETWEEN 09 AND 12Z. IN ADDITION TO LOWER CEILINGS, AREAS OF -RA COULD BEGIN TO MOVE IN AFTER 00Z AS WELL. HOWEVER, IT IS UNLIKELY THAT ANY TAF SITES WILL BE AFFECTED BEFORE 06Z. IF RA DOES MOVE IN, COULD SEE VISIBILITIES REDUCED TO MVFR AT TIMES. AT THIS TIME, KACY, KMIV, KILG, AND KPHL HAVE THE HIGHEST CHANCES OF SEEING MVFR CONDITIONS BEFORE 12Z. WED AND WED EVENING... WIDESPREAD MVFR AND IFR CONDS, MAINLY WITH CIGS BUT SOME VSBY RESTRICTIONS AS WELL, ESPECIALLY IN THOSE AREAS THAT SEE SNOW OR HVY RAIN. FOR NRN AND WRN AREAS (KABE/KRDG)...MOSTLY SNOW IS EXPECTED. ALONG THE I-95 CORRIDOR, THE PRECIP WILL START OFF AS RAIN, WITH TEMPS ABV FREEZING THEN WILL MIX WITH SNOW AND CHANGE OVER AT SOME POINT WED AFTN OR EVE BEFORE ENDING. FOR SRN AND ERN AREAS PRECIP WILL BE MOSTLY OR ALL RAIN. WIND WILL GUST IN THE 15 TO 25 KT RANGE AS WELL, MAINLY FROM THE N. PRECIP SHUD END DURG WED EVE. CONFIDENCE IS HIGH ABOUT THE EVENT, BUT LOW ABOUT PRECIP TYPE ALG THE I-95 CORRIDOR. OUTLOOK.... THU...CONDS RETURN TO VFR AND WINDS SHIFT TO WESTERLY OR NORTHWEST. THERE COULD BE BRIEF MVFR CONDITIONS IN SCATTERED SNOW SHOWERS LATER THURSDAY MAINLY JUST N OF KRDG AND KABE. WINDS MAY GUST TO 25 KT. FRI THRU SAT...VFR CONDITIONS EXPECTED. && .MARINE... WINDS AND SEAS WILL BE SLOW TO DECREASE ONCE THE COLD FRONT MOVES OFF SHORE BY SUNRISE. ONCE WINDS AND SEAS DO FALL BELOW SCA CRITERIA THIS MORNING ON THE BAY, AND LATE THIS AFTERNOON ON THE ATLANTIC COASTAL WATERS, THERE WILL BE A BRIEF LULL WITH SUB SCA CONDITIONS BEFORE NORTHEASTERLY WINDS INCREASE QUICKLY AFTER MIDNIGHT IN RESPONSE TO THE APPROACHING LOW. BY EARLY TOMORROW MORNING, GALE CONDITIONS ARE LIKELY ON THE LOWER DELAWARE BAY AND THE ATLANTIC COASTAL WATERS. WED...A GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS AND LOWER DELAWARE BAY PER AN INTENSIFYING STORM MOVING NEWD FROM THE NC COAST. SCA CONDITIONS EXPECTED ON THE UPPER DELAWARE BAY. THE 06Z NAM IS ADVERTISING A PERIOD OF STORM FORCE WINDS VCNTY 44009. WE WILL NOT KNOW FOR SURE SINCE NO 44009 WIND DATA. WED NIGHT...GALE CONDITIONS WILL CONTINUE EARLY, THEN SEAS AND WIND WILL DECREASE AND AND SCA WILL BE LIKELY NEEDED AS THE STORM MOVES NORTHEAST OF CAPE COD. OUTLOOK... THU...WIND AND SEAS CONTINUE TO DIMINISH BUT SCA WILL BE NEEDED PROBABLY THU AFTN OR EVE. FRI THROUGH SAT..WIND AND SEAS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA. && .CLIMATE... REGARDING THE MIDWEEK COASTAL STORM BRINGING SNOW TO A LARGE PORTION OF OUR REGION, WE HAVE INCLUDED DAILY SNOWFALL RECORDS BELOW FOR OUR FOUR PRIMARY CLIMATE SITES THAT HAVE A LONG-STANDING UNBROKEN PERIOD OF RECORD (POR) WITH RESPECT TO HISTORICAL SNOWFALL DATA. DAILY SNOWFALL RECORDS: NOVEMBER 26TH: NOVEMBER 27TH: PERIOD OF RECORD: ACY: TRACE 1977,1957,1955 1.2 INCHES 1978 1874 PHL: 6.0 INCHES 1898 6.9 INCHES 1949,1938 1872 ILG: 0.1 INCHES 1950 4.5 INCHES 1978 1894 ABE: 1.7 INCHES 1925 7.0 INCHES 1938 1922 OTHER COOPERATIVE SITE SHORTER HISTORICAL RECORD CAN BE FOUND AT THE NWS MOUNT HOLLY WEBSITE UNDER NOW DATA. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 1 AM EST THURSDAY FOR PAZ054-055. WINTER STORM WATCH LATE WEDNESDAY NIGHT FOR PAZ054-055. WINTER STORM WARNING FROM 7 AM TO 10 PM EST WEDNESDAY FOR PAZ060>062-101-103-105. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR PAZ070-071-102-104-106. NJ...WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 1 AM EST THURSDAY FOR NJZ001-007-008. WINTER STORM WATCH LATE WEDNESDAY NIGHT FOR NJZ001-007-008. WINTER STORM WARNING FROM 7 AM TO 10 PM EST WEDNESDAY FOR NJZ009. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR NJZ010-015. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ450>455. GALE WARNING FROM 4 AM TO 10 PM EST WEDNESDAY FOR ANZ431- 450>455. SMALL CRAFT ADVISORY FROM 4 AM TO 10 PM EST WEDNESDAY FOR ANZ430.
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&& $$ SYNOPSIS...NIERENBERG NEAR TERM...DRAG/JOHNSON SHORT TERM...DRAG/JOHNSON LONG TERM...NIERENBERG AVIATION...DRAG/JOHNSON/NIERENBERG MARINE...DRAG/JOHNSON/NIERENBERG CLIMATE... UPDATED FOR THE WARNING IN WWA SECTION

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