Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 310509 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 109 AM EDT TUE MAR 31 2015 .SYNOPSIS... A FAST MOVING LOW PRESSURE SYSTEM SHOULD SWEEP THROUGH THE AREA LATER TODAY. A HIGH PRESSURE SYSTEM WILL BUILD INTO THE REGION FOR WEDNESDAY AND MOVE OFFSHORE ON THURSDAY. THE NEXT COLD FRONT SHOULD MOVE THROUGH THE REGION LATE FRIDAY. A SECONDARY COLD FRONT SHOULD MOVE THROUGH THE AREA LATE SATURDAY FOLLOWED BY A HIGH PRESSURE SYSTEM FOR THE START OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... FOR THIS ESTF UPDATE WE EXTENDED PCPN CHANCES DEEPER INTO THE OVERNIGHT CLOSE TO THE INTERSTATE 80 CORRIDOR. SOME SLIGHT TEMPERATURE ADJUSTMENTS WERE MADE BASED ON CURRENT OBS. THE S/WV CROSSING THE REGION HAS TOUCHED OFF AN AREA OF PRECIP OVER NRN AREAS. IT HAS BEEN PREDOMINANTLY RAIN, THOUGH SOME SN WAS REPORTED IN THE POCONOS. EXPECT THIS PRECIP TO CONTINUE FOR THE NEXT FEW HOURS. THIS PRECIP IS SUPPORTED BY THE HRRR. HAVE INTRODUCED SOME LOW POPS ACRS THE NRN TIER ACCORDINGLY. HAVE ALSO INCREASED CLOUD COVER IN THIS AREA. ONCE THIS PRECIP MOVES THRU, EXPECT A DRY NIGHT AND A QUIET NIGHT ELSEWHERE. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... A FAST MOVING CLIPPER SYSTEM WILL BE GOOD FOR ABOUT 6 HOURS OF PRECIPITATION ACROSS THE AREA TUESDAY. THE GOOD NEWS IS THAT MOST AREAS WILL HAVE RAIN. ONLY THE HIGHER ELEVATIONS OF THE SRN POCONOS WILL HAVE SNOW TUE WITH A SMALL ACCUMULATION...1 TO 2 INCHES POSSIBLE. THE PRECIPITATION WILL ARRIVE ACROSS THE WEST DURING THE LATE MORNING AND WILL OVERSPREAD THE DEL VALLEY/DELMARVA AND NJ BY AFTERNOON. OVERALL QPF OF ABOUT 0.25 EXPECTED. HIGH TEMPERATURES TUE WILL RANGE FROM THE LOW/MID 40S NORTH TO THE MID 50S SOUTH. HIGHS WILL REMAIN CLOSER TO THE MID 30S OVER THE HIGHER ELEVATIONS NORTH. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... LONG TERM BEGINS WITH A SPLIT FLOW PATTERN AND THE DEPARTING CLIPPER SYSTEM, BUT BY THE END OF THE WEEK WE SEE THE UPPER LEVEL PATTERN TRANSITION TO MORE OF A ZONAL FLOW PATTERN. TUESDAY NIGHT...CLIPPER SYSTEM EXITS. MODELS ARE IN RELATIVELY GOOD AGREEMENT OF HOW QUICKLY IT WILL EXIT (WITH PRECIP CUTTING OFF FOR ALL BUT COASTAL AREAS BY 06Z), EVEN THOUGH THERE REMAIN SOME MINOR DIFFERENCES WITH THE TRACK OF THE LOW. WEDNESDAY AND THURSDAY...SURFACE HIGH BUILDS OVER OUR REGION WEDNESDAY, BUT QUICKLY SHIFTS OFF SHORE. AS IT DOES SO, LOW LEVEL FLOW WILL BECOME MORE SOUTHERLY AND SOUTHWESTERLY RESULTING IN SIGNIFICANT WARM AIR ADVECTION. HIGHS ON THURSDAY SHOULD BE ABOUT 10 TO 15 DEGREES HIGHER THAN WEDNESDAY, AND ABOVE NORMAL! THURSDAY NIGHT INTO SATURDAY...MODELS CAME INTO CONSIDERABLY BETTER AGREEMENT OVER THE LAST 24 HOURS, WITH THE GFS GENERALLY TRENDING MORE TOWARDS THE ECMWF SOLUTION. MODELS ARE IN RELATIVELY GOOD CONSENSUS THAT WE WILL STAY IN THE WARM SECTOR THURSDAY NIGHT INTO EARLY FRIDAY UNTIL THE INITIAL COLD FRONT SLOWLY SLIDES THROUGH FRIDAY AFTERNOON INTO FRIDAY NIGHT. THROUGH THIS TIME THOUGH, A WEAK UPPER LEVEL SHORT WAVE TROUGH, AND BEING UNDER THE RIGHT REAR QUADRANT OF AN UPPER LEVEL JET WILL ALLOW FOR SOME CHANCES OF RAIN EVEN BEFORE THE FRONT ENTERS THE REGION. CHANCE FOR RAIN CONTINUE WITH THE PASSAGE OF THE FRONT AND AS THE NEXT UPPER LEVEL JET APPROACHES THE REGION. SUNDAY INTO MONDAY...STILL CONSIDERABLE UNCERTAINTY HOW QUICKLY THE NEXT COLD FRONT WILL MOVE INTO THE REGION, AND WHEN IT DOES IF THERE WILL BE ANY PRECIPITATION. FOR NOW, CONTINUED TO KEEP THE FRONTAL PASSAGE DRY AS THERE WILL BE LIMITED OPPORTUNITY FOR MOISTURE ADVECTION BETWEEN THE TWO FRONTAL PASSAGES. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. THE 06Z TAFS WILL BRING ALL OF OUR SITES TO LOW MVFR OR IFR CONDITIONS THIS AFTERNOON WITH A HIGH DEGREE OF UNCERTAINTY ABOUT THE WIND DIRECTIONS THIS AFTERNOON AND EARLY EVENING. REST OF THE OVERNIGHT VFR WITH SOME MID TO HIGH LEVEL CLOUDS. LIGHT WEST WINDS. THIS MORNING A MID LEVEL CIG ARRIVING, SOME RAIN POSSIBLE LATE AT KABE AND KRDG. SOUTH TO SOUTH WEST WINDS AVERAGING 5 TO 10 KNOTS. THIS AFTERNOON AT KABE AND KRDG CIGS AND VSBYS LOWERING TO IFR. RAIN MAY MIX WITH OR CHANGE TO SNOW LATE. ESP KABE. TARMAC ACCUMS NOT EXPECTED. LOCAL KPHL AIRPORTS RAIN ARRIVES AND CIGS AND VSBYS LOWERING TO THE BORDER BETWEEN MVFR AND IFR CONDITIONS. KMIV AND KACY SIMILAR EVOLUTION, BUT LATER IN THE AFTERNOON. WINDS WILL BE TRICKY AS IT DEPENDS UPON THE TRACK OF THE LOW. WE ARE EXPECTING IT TO PASS TO THE SOUTH OF ALL THE TERMINALS ACROSS DELMARVA. THERE WILL BE A SLOW BACKING OF THE WINDS FROM SOUTH TO NORTHEAST AS THE AFTERNOON PROGRESSES. SPEEDS SHOULD BE AROUND 10 KNOTS. THIS EVENING, CONDITIONS BOTTOMING EAST OT IFR EARLY AND THEN IMPROVING CONDITIONS THE REST OF THE EVENING. PCPN SHOULD END BY 04Z ALL TERMINALS. WINDS WILL CONTINUE TO BACK TOWARD THE NORTH AND THEN NORTHWEST WITH AVERAGE SPEEDS AROUND 10 KNOTS, BUT SOME GUSTINESS TO AROUND 20 KNOTS FROM THE KPHL AIRPORTS SOUTHEASTWARD. OVERNIGHT IMPROVING CONDITIONS CONTINUING WITH A VFR CIG BECOMING CLEAR AND NORTHWEST WINDS AVERAGING AROUND 10 TO 15 KNOTS. OUTLOOK... WEDNESDAY THROUGH THURSDAY...GENERALLY VFR CONDITIONS. BREEZY SOUTHWESTERLY WINDS LATER ON THURSDAY. THURSDAY NIGHT THROUGH FRIDAY NIGHT...MVFR CONDITIONS EXPECTED WITH RAIN SHOWERS. SLIGHT CHANCE OF THUNDERSTORMS THURSDAY NIGHT INTO FRIDAY MORNING AS THE FRONT MOVES THROUGH. SATURDAY...CONDITIONS IMPROVING AS PRECIPITATION MOVES OUT.
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&& .MARINE... BASED ON THE LATEST OBSERVATIONS, ALL FLAGS WILL BE DROPPED WITH THE LATEST FCST UPDATE. OVERALL, A W WIND IS ANTICIPATED AND COULD GUST AS HIGH AS 20 KT, BUT EVEN THAT HAS BEEN GENEROUS SUB-SCA LATE AFTER THAT AND INTO TUE MORNING. THE NEXT CLIPPER TUE COULD ONCE AGAIN PRODUCE SCA WINDS TUE AFTERNOON INTO THE EVENING. OUTLOOK... TUESDAY NIGHT...WINDS AND SEAS SHOULD REMAIN JUST BELOW SCA CRITERIA. WEDNESDAY...SUB SCA CONDITIONS EXPECTED. THURSDAY THROUGH FRIDAY...SOUTHERLY AND SOUTHWESTERLY WINDS WILL LIKELY INCREASE ABOVE 25 KT FOR AT LEAST PART OF THIS PERIOD. SEAS ON THE OCEAN WILL LIKELY INCREASE TO SCA CRITERIA AS WELL. AGREE WITH PREVIOUS SHIFT THAT WAVE WATCH GUIDANCE IS A BIT TOO HIGH FOR WAVE HEIGHTS WITH THIS PATTERN, SO UNDERCUT GUIDANCE SLIGHTLY. SATURDAY...CONSIDERABLE UNCERTAINTY, BUT WAVES ABOVE 5 FT ARE POSSIBLE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...JOHNSON NEAR TERM...GIGI/NIERENBERG/O`HARA SHORT TERM...O`HARA LONG TERM...JOHNSON AVIATION...GIGI/JOHNSON MARINE...JOHNSON/NIERENBERG/O`HARA

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