Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 131938 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 338 PM EDT SAT SEP 13 2014 .SYNOPSIS... LOW PRESSURE WILL TRACK INTO THE CANADIAN MARITIMES THROUGH TONIGHT. HIGH PRESSURE WILL THEN BUILD ACROSS THE MID ATLANTIC REGION FOR SUNDAY AND MONDAY. A COLD FRONT IS EXPECTED TO QUICKLY CROSS OUR REGION LATER MONDAY NIGHT AND EARLY TUESDAY, WITH HIGH PRESSURE ARRIVING WEDNESDAY INTO THURSDAY. A WEAK COLD FRONT MAY THEN SETTLE ACROSS OUR AREA THURSDAY, FOLLOWED BY HIGH PRESSURE BUILDING IN FRIDAY BEFORE SHIFTING OFFSHORE DURING SATURDAY. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 130 PM UPDATE MAINLY DRESSING UP THE PRIOR AFD AND ESTF: NO CHANGES ESTF SINCE ~1230 PM. WE ADDED PATCHY FOG KMPO. OTRW ITS A NEAR 100 PCT CHC FOR A BAND OF SHOWERS..SOME BRIEFLY MDT OR HEAVY HEADING EWD ACROSS THE FCST AREA THIS AFTN. THE GRIDS ATTEMPT TO DEFINE. WE DONT HAVE THE "HEAVY" RAIN WORDING IN THE FCST BUT FOR THOSE ATTENDING OUTDOOR ACTIVITY...PREPARE FOR A WET CHILLING PERIOD THIS AFTN. IT DRIES OUT LATE IN THE DAY FROM KRDG TO KMPO WITH JUST MAYBE A SPRINKLE. THE CAUSE IS A COLD FRONT ALOFT WITH A NICE BC ZONE OF ENHANCED CLOUDS WITH THE IR IMAGERY COOLING SINCE 14Z THRU 17Z FROM ELMIRA TO ELKINS WVA. THE INSTABILITY BURST IN THE WAA AHEAD OF THE COLD FRONT PERMITS HEAVIER SHOWERS TO DEVELOP VICINITY THE I95 CORRIDOR THIS AFTN WITH PWAT INCREASING FROM THE 12Z ~1.25 INCHES TO 18Z ~ 1.9 INCHES. TEMPS WILL STRUGGLE TO RISE MUCH PAST 55 IN THE POCONOS AND 60S ELSEWHERE IN PA...70 OVER THE I95 CORRIDOR AND MID 70S PORTIONS OF THE COAST. THIS IS GENERALLY 5 TO 10 DEGREES BELOW NORMAL FOR THIS TIME OF YEAR. RADAR WISE...EARLIER TODAY IT APPEARED THE LEGACY STP WAS MORE CONSERVATIVE AND MORE ACCURATE THAN THE DUAL POL STA PRODUCT. TONIGHT...BAROCLINIC ZONE SCT SHOWERS WILL BE ENDING FROM WEST TO EAST EARLY THIS EVENING....GENERALLY PRIOR TO 00Z/14. SKIES WILL CLEAR TONIGHT AND THE REST OF THE NIGHT LOOKS DRY AND PLEASANTLY COOL WITH TEMPS DROPPING INTO THE 40S AND 50S. A BIT OF A NNW BREEZE MAY DEVELOP IN THE GRADIENT ISOBARIC NORTHERLY FLOW. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... BRILLIANT SUNSHINE AND PLEASANT, 5 DEGREE BELOW AVERAGE DAYTIME TEMPERATURES ARE IN STORE, WITH HIGHS RANGING FROM THE 60S THROUGH THE SOUTHERN POCONOS AND PARTS OF NORTHWEST NJ TO MAINLY THE LOWER 70S ELSEWHERE. SOME AFTERNOON STRATOCU CLOUDINESS SHOULD FORM IN THE NE PA HILLS AND MOUNTAINS AS WELL AS NW NJ AND THERE WILL BE SOME PATCHY THIN CIRRUS AROUND 30000 FT MIDDAY. NOTE: DEWPOINTS ARE FCST TO LOWER TO NEAR 40 ON SUNDAY! && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... THE OVERALL SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH STRETCHED FROM THE NORTHERN PLAINS ALL THE WAY TO THE NORTHEAST THROUGH TUESDAY. SOME SHORT WAVES EMBEDDED IN THE FLOW WILL AMPLIFY THE TROUGH SOME EASTWARD A FEW TIMES. AN UPPER-LEVEL RIDGE IS THEN FORECAST TO MIGRATE ACROSS THE MIDDLE OF THE NATION FRIDAY, ALLOWING THE TROUGH TO TRY AND LIFT OUT OF THE NORTHEAST WITH A POTENTIAL RIDGE BUILDING ACROSS PORTIONS OF THE EAST AND ALSO THE SOUTHERN STATES. THIS WILL EVENTUALLY DRIVE AN EXPANSIVE SURFACE HIGH OVER THE REGION, ALTHOUGH THEN SHIFTING OFFSHORE SATURDAY. A MODEL BLEND WAS USED FOR SUNDAY NIGHT THROUGH TUESDAY, THEN UTILIZED THE 12Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR SURROUNDING OFFICES. FOR SUNDAY NIGHT AND MONDAY...AN EXPANSIVE SURFACE HIGH IS FORECAST TO BUILD ACROSS THE GREAT LAKES AND INTO OUR REGION SUNDAY, THEN SHIFT OFFSHORE THROUGH MONDAY. THIS SURFACE HIGH IS CHARACTERIZED BY A COOL AIRMASS, THEREFORE DRY AND COOL/CHILLY CONDITIONS ARE ANTICIPATED SUNDAY NIGHT BEFORE SOME MODERATION OCCURS ON MONDAY. A SHORT WAVE LOOKS TO DIVE ACROSS THE MIDWEST AND GREAT LAKES MONDAY AND AN ASSOCIATED WEAK SURFACE LOW SHOULD ACCOMPANY IT. THIS FEATURE WILL TAKE AIM ON OUR AREA LATER MONDAY NIGHT WITH SOME WAA AHEAD OF IT, THEREFORE AN INCREASE IN THE CLOUDS WILL OCCUR ESPECIALLY AT NIGHT. THE ARRIVAL OF LARGE SCALE LIFT COMBINED WITH SOME DEEPER MOISTURE SHOULD ALLOW FOR A RIBBON OF SHOWERS TO DEVELOP AT NIGHT. WHILE THERE IS SOME QUESTION ON HOW ORGANIZED THE SHOWERS WILL BE AS THE SYSTEM IS GENERALLY MOVING QUICKLY, ENOUGH MOISTURE AND LIFT SHOULD GENERATE A TIME OF FAIRLY WIDESPREAD SHOWERS. THEREFORE THE POPS WERE INCREASED THROUGH THE NIGHT FROM WEST TO EAST WITH LIKELY POPS INDICATED LATE. FOR TUESDAY...AN AMPLIFYING UPPER-LEVEL TROUGH WILL SWING ACROSS THE NORTHEAST AND MID ATLANTIC REGION TUESDAY, TAKING LOW PRESSURE WITH IT. THIS FEATURE LOOKS TO BE PROGRESSIVE, THEREFORE A BIT UNSETTLED IN THE MORNING THEN IMPROVING CONDITIONS SHOULD SET IN DURING THE AFTERNOON AND AT NIGHT. THE INFLUX OF DRIER AND COOLER AIR ALONG WITH INCREASING SUBSIDENCE SHOULD ALLOW FOR CLEARING TO TAKE PLACE ESPECIALLY AT NIGHT. THERE COULD BE SOME LINGERING STRATOCUMULUS WITHIN THE CAA REGIME ESPECIALLY TOWARD THE NORTHWEST ZONES. FOR WEDNESDAY THROUGH FRIDAY...WHILE AN UPPER-LEVEL TROUGH IS FORECAST TO BE IN PLACE WEDNESDAY INTO THURSDAY, SURFACE HIGH PRESSURE WILL ARRIVE FROM THE WEST. THIS WILL DELIVER ANOTHER ROUND OF MUCH DRIER AIR ALONG WITH A COOL AIRMASS FOR WEDNESDAY AND THURSDAY. A WEAK COLD FRONT HOWEVER MAY TRY AND SETTLE SOUTHEASTWARD ACROSS OUR AREA THURSDAY, WITH A NEW AIRMASS AND ASSOCIATED SURFACE HIGH PRESSURE BUILDING BACK IN FOR FRIDAY. THE FRONT LOOKS TO HAVE LIMITED MOISTURE WITH IT, THEREFORE KEPT THE FORECAST DRY. MOST OF THE WEATHER ELEMENTS WERE FAIRLY CLOSE TO THE 12Z WPC GUIDANCE. FOR SATURDAY...A BUILDING RIDGE MAINLY TO OUR SOUTH AND EAST SHOULD SUPPORT AN EXPANSIVE SURFACE HIGH THAT WILL BE SHIFTING TO OUR EAST. THE PLACEMENT OF THIS HIGH WILL BE CRUCIAL IN DETERMINING OUR SENSIBLE WEATHER, AS AN ONSHORE FLOW MAY RESULT AND CAUSE MORE CLOUDINESS DUE TO THE OCEAN INFLUENCE. THIS COULD BE ENHANCED SOME AS LOW PRESSURE MAY DEVELOP ALONG A STALLED FRONTAL BOUNDARY OFF THE CAROLINA COAST, RESULTING IN A TIGHTENING PRESSURE GRADIENT IN THE MID ATLANTIC REGION. OVERALL, LESS CERTAINTY WITH THE DETAILS THIS FAR OUT AND THEREFORE WE STAYED CLOSE TO THE 12Z WPC GUIDANCE. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REMAINDER OF THIS AFTERNOON...MOSTLY MVFR CIGS WITH OCNL 1-4 MI VSBY IN SHOWERS. LIGHT E WIND GUST 10-15 KT. SHOWERS END BY 19Z KRDG AND 20Z KABE. TONIGHT...VFR CIGS EARLY WITH POSSIBLE LEFTOVER MVFR CIGS THEN BECOMING CLEAR BY 04Z/14 WITH JUST A SMALL CHC OF PATCHY IFR CIGS KMIV AND KACY FOR A SHORT TIME THIS EVENING IN THE INITIALLY LIGHT NW FLOW. NNW WIND MAY BECOME GUSTY 18 KT LATE AT NIGHT. SUNDAY...VFR CLEAR OR MOSTLY CLEAR CONDITIONS WITH A NORTH-NORTHWEST WIND GUSTY 10-15 KT DIMINISHING AS THE DAY MOVES ALONG. OUTLOOK... SUNDAY NIGHT...VFR WITH WINDS BECOMING MAINLY LIGHT AND VARIABLE. MONDAY AND TUESDAY...MAINLY VFR. SOME SHOWERS SHOULD MOVE THROUGH LATE MONDAY NIGHT AND TUESDAY MORNING WITH BRIEF SUB-VFR CONDITIONS. SOUTHWESTERLY WINDS GENERALLY 5-10 KNOTS, BECOMING NORTHWESTERLY LATER MONDAY NIGHT INTO TUESDAY. WEDNESDAY AND THURSDAY...VFR OVERALL AS HIGH PRESSURE BUILDS IN. && .MARINE... WINDS AND SEAS ARE FCST TO REMAIN JUST BELOW SCA CRITERIA THROUGH EARLY AFTERNOON AS A COASTAL LOW TAKES SHAPE AND HEADS NE. GUSTS AROUND 25 HAVE OCCURRED AROUND BRICK AND SANDY HOOK NJ BUT OVERALL THE WEATHER FLOW DATA TRENDS ARE STEADY SLOWLY DIMINISHING SINCE 16Z. SCA WILL LIKELY BE NEEDED FROM MIDNIGHT ONWARD LATE TONIGHT IN THE GRADIENT NNW COOL AIR ADVECTION BEHIND THE COLD FRONT. HOWEVER, CONFIDENCE IS MODEST. THE 12Z GFS WW GUIDANCE FOR THE SEAS PUSHES 5 FEET FOR AT LEAST 5 HOURS LATE AT NIGHT AT 44009 AND THE BL WIND SHOULD INCREASE TO 20 KT ON THE COASTAL WATERS AFFORDING SCT GUSTS TO NEAR 25 KT. SUNDAY...POSSIBLE MARGINAL SCA CONDITIONS FOR THE COASTAL WATERS. CONFIDENCE BELOW AVERAGE. THE GRADIENT BETWEEN A DEPARTING SYSTEM TO THE NORTHEAST AND INCOMING HIGH PRESSURE TO OUR WEST MAY YIELD SOME WIND GUSTS BETWEEN 20 TO 25 KNOTS AND SEAS INTO THE 4-5 FOOT RANGE FOR OUR ATLANTIC COASTAL WATERS THROUGH SUNDAY MORNING. WINDS AND SEAS ARE EXPECTED TO MARKEDLY DECREASE DURING SUNDAY AFTERNOON AS HIGH PRESSURE BUILDS OVER THE REGION AND AREA WATERS. OUTLOOK... SUNDAY NIGHT...THE WINDS AND SEAS ARE ANTICIPATED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA AS HIGH PRESSURE BUILDS OVER THE AREA. MONDAY AND TUESDAY...A QUICK MOVING SYSTEM WILL MOVE THROUGH LATER MONDAY NIGHT AND TUESDAY MORNING ALLOWING FOR A WIND SHIFT TO OCCUR. DESPITE THE WINDS SHIFTING TO THE NORTHWEST OR NORTH TUESDAY AND INCREASING SOME, IT APPEARS THAT THE WINDS AND SEAS OVERALL REMAIN BELOW ADVISORY CRITERIA. WEDNESDAY AND THURSDAY...A NORTH TO NORTHEAST FLOW COULD BE A BIT GUSTY AT TIMES AND THIS WILL BUILD THE SEAS SOME. HOWEVER, THE WINDS SHOULD BE BELOW ADVISORY CRITERIA BUT THE SEAS AS OF NOW MAY NEAR 5 FEET MAINLY TOWARD THE OUTER EDGE OF THE COASTAL WATERS. && .RIP CURRENTS... THERE IS A MODERATE RISK OF RIP CURRENTS THIS AFTERNOON. && .CLIMATE... IT SEEMS WORTHWHILE TO NOTE THAT THE PRECIPITATION ACCUMULATION DEPARTURE FROM NORMAL THE PAST TWO WEEKS (NOT INCLUDING TODAY) IS WELL BELOW NORMAL FOR E PA AND NW NJ AS WELL AS CENTRAL DE. FOR NW NJ AND CENTRAL-SRN DE THAT MIRRORS THE 90 DAY ANALYSIS OF 50 TO 75 PCT OF NORMAL PCPN THIS PAST SUMMER. THE 46 MEMBER NAEFS HAS NOT DONE SO WELL ON MODELING THE SUBSTANTIAL 4 DEGREE OR GREAT POSITIVE TEMPERATURE ANOMALY THAT HAS OCCURRED HERE IN THE NORTHEASTERN QUADRANT OF THE COUNTY THE FIRST 12 DAYS OF THE MONTH...YET WAS ACCURATELY OUTLOOKING DEPARTURES IN THE PLAINS AND NORTHERN ROCKIES AS WELL AS GULF COAST. HOWEVER...THE NAEFS HAS HAD A RECENT SIGNIFICANT COLD BIAS IN OUR AREA. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EDT SUNDAY FOR ANZ452>455. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EDT SUNDAY FOR ANZ431. && $$ SYNOPSIS...GORSE NEAR TERM...DRAG SHORT TERM...DRAG LONG TERM...GORSE AVIATION...DRAG/GORSE MARINE...DRAG/GORSE RIP CURRENTS... CLIMATE...

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