Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 272001 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 401 PM EDT FRI MAR 27 2015 .SYNOPSIS...
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LOW PRESSURE AND A ASSOCIATED COLD FRONT WILL CONTINUE MOVING OFFSHORE TONIGHT. HIGH PRESSURE WILL BUILD EASTWARD FROM THE OHIO VALLEY INTO THE MID-ATLANTIC STATES THIS WEEKEND. A COUPLE OF COLD FRONTS AND ASSOCIATED LOW PRESSURE SYSTEMS WILL MOVE THROUGH EARLY NEXT WEEK. HIGH PRESSURE WILL THEN BUILD BACK INTO THE REGION WEDNESDAY INTO THURSDAY BEFORE ANOTHER COLD FRONT MOVES THROUGH THE REGION BY FRIDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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A COLD FRONT HAS PUSHED WELL OFFSHORE AND COOLER AIR IS ADVECTING ACROSS THE AREA ON NNW LOW-LEVEL WINDS. HOWEVER AN UPPER LEVEL TROF REMAINS TO THE W/NW ACROSS THE GRTLKS AND IS MOVING ONLY SLOWLY SEWD. THE RESULT IS SWLY FLOW ALOFT ACROSS THE MID-ATLANTIC REGION WHICH IS CONTG TO BRING MOISTURE AND LIGHT RAIN ACROSS MUCH OF DELMARVA AND FAR SERN NJ. THE MOSAIC RADAR LOOP SUGGESTS THAT THE LAST BATCH OF RAIN MAY BE MOVG ACROSS CENTRAL DELMAVA AS OF MID AFTERNOON. FOR THAT AREA WE HAVE CHANCE POPS FOR THE REMAINDER OF THE AFTERNOON DECREASING TO SLIGHT CHANCE THIS EVENING AND BELOW MENTIONABLE THRESHOLD OVERNIGHT. FOR TONIGHT...EXPECT MID/HI LEVEL CLOUDS TO REMAIN OVER THE AREA AS THE UPPER LEVEL TROF REMAINS TO THE NW. CLOUDS WILL LIMIT COOLING IN SPITE OF CONTD LOW-LEVEL COLD ADVCTN. IN FACT IT LOOKS LIKE A SECONDARY SURGE OF COLD AIR WILL MOVE IN OVERNIGHT WITH STRONGER NNW WINDS DEVELOPING. A BLEND OF MOS GUIDANCE WAS USED FOR THE MIN TEMPS WHICH SHOULD BE ROUGHLY 10 DEG F COLDER THAN THIS MORNING.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
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HIGH PRES WILL CONTINUE TO BUILD IN FROM THE WEST ON SATURDAY...BUT THE UPPER-LEVEL TROF WILL ALSO BE MOVG ACROSS THE AREA. DEEP-LAYER MOISTURE WILL GENERALLY BE DECREASING AND THERE DOES NOT SEEM TO BE ANY ORGANIZED UVV. HWVR...WITH COLD AIR ALOFT ANY BREAKS IN THE CLOUDS AND SFC HEATING MAY RESULT IN SOME INSTABILITY AND POSSIBLY SOME SCATTERED SNOW/RAIN SHOWERS. COLD 850 MB TEMPS WOULD CERTAINLY SUPPORT SNOW...HWVR WARMER/DRIER AIR BELOW COULD CAUSE MELTING OR EVAPORATION BEFORE SNOW REACHES THE GROUND...ESPECIALLY FROM PHL SWD AND EWD.
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&& .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
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THE MAJORITY OF THIS FORECAST PERIOD WILL BE DOMINATED BY QUICK MOVING COLD FRONTS IN A NORTHWEST FLOW PATTERN WITH CHANCES FOR LIGHT PRECIPITATION. BY LATE IN THE WEEK, THE POTENTIAL FOR A WARMER PATTERN WITH MORE SOUTHERLY FLOW EXISTS. SATURDAY NIGHT THROUGH SUNDAY: FAIRLY QUIET OVERALL WITH HIGH PRESSURE MOVING SOUTH OF THE REGION. SETUP IS VERY FAVORABLE FOR RADIATIONAL COOLING IN THE PINE BARRENS AND ACROSS PARTS OF EASTERN PA WITH CLEAR SKIES AND LIGHT WINDS. CHILLY WITH LOWS IN THE 20`S ACROSS MOST OF THE REGION. TEMPERATURES SHOULD REBOUND INTO THE 40`S SUNDAY AFTERNOON, WITH MODELED TWO METER TEMPERATURES TO COOL. SUNDAY NIGHT AND MONDAY: A COLD FRONT WILL MOVE THROUGH THE REGION MONDAY MORNING. THE PARENT LOW PRESSURE SYSTEM WILL BE LOCATED OVER SOUTHEAST CANADA WITH LIMITED MOISTURE TRANSPORT NORTH. BOTH OF THESE FACTORS KEEP PRECIPITATION LIGHT AND IN THE CHANCE RANGE ATTM. LOW TEMPERATURES NEAR FREEZING NORTHWEST WARRANT MIXED P-TYPE CHANCES ATTM WITH NO WINTRY ACCUMULATION. WITH MORE CLOUDS, LOW TEMPERATURES WILL STAY IN THE 30`S WITH LIGHT SOUTHERLY FLOW. EVEN WITH A WIND DIRECTION CHANGE TO WEST/NORTHWEST ON MONDAY, 925 MB TEMPERATURES DON`T FALL MUCH AND THE POTENTIAL FOR SOME PEAKS OF SUN EXISTS IN THE AFTERNOON. SO WILL GO WITH THE WARMER ECM AND MEX GUIDANCE. WIND GUSTS AROUND 20-25 MPH ARE POSSIBLE MONDAY AFTERNOON WITH SOME MIXING POTENTIAL. MONDAY NIGHT AND TUESDAY: A RETURN TO LIGHT SOUTHERLY FLOW AHEAD OF THE NEXT SYSTEM. MODEL DIVERGENCE IN THE TRACK OF THESE NORTHWEST FLOW SYSTEMS DIVING SOUTHEAST OF CANADA STARTS TO VARY IN THIS PERIOD. FAIRLY TIGHT SPREAD IN ALL GUIDANCE ON THE TEMPERATURES WITH MOST LOCATIONS GETTING INTO THE 50`S AFTER A CHILLY START IN THE 30`S. TUESDAY NIGHT AND WEDNESDAY: THE 12Z GFS AND 00Z ECMWF/UKMET ARE SIMILAR WITH THE TRACK OF A LOW PRESSURE SYSTEM TRACKING IT ACROSS SOUTHERN NEW ENGLAND CLOSE TO THE WPC PROGS. THE CMC LOOKS TO FAR SOUTH WITH THE TRACK. THIS BRINGS A CHANCE OF RAIN SHOWERS AND LIGHT QPF, HIGHEST CHANCES ACROSS THE NORTH. TEMPERATURES MAY RISE LATE TUESDAY NIGHT SOUTH OF THE LOW TRACK. STAYED CLOSE TO ENSEMBLE GUIDANCE IN THIS PERIOD FOR MOST WEATHER ELEMENTS. WEDNESDAY NIGHT THROUGH FRIDAY: THE POTENTIAL EXISTS FOR A STRONGER RIDGE TO DEVELOP OFF THE EAST COAST NEAR BERMUDA. THIS WOULD HAVE THE EFFECT OF INCREASING SOUTHERLY FLOW, PUMPING A MILDER AIRMASS INTO THE REGION. MODELED 925 MB TEMPERATURES RESPOND NICELY TO THIS PATTERN CHANGE IN THIS TIME PERIOD. WILL TAKE THE FORECAST ON THE WARMER SIDE OF THE GUIDANCE RANGE IN THIS TIMEFRAME. A STRONGER COLD FRONT COULD LEAD TO ANOTHER SHOWER CHANCE BY THURSDAY AFTERNOON WITH THE 12Z GFS THE MOST AGGRESSIVE. IN TERMS OF ANY THUNDERSTORMS, SHEAR WILL LIKELY BE ABUNDANT AHEAD OF THE FRONT WITH INSTABILITY LACKING BUT POSSIBLY ENOUGH FOR A FEW RUMBLES OF THUNDER. STILL A CONSIDERABLE TIME TO EXAMINE ANY THUNDER THREAT WITH THIS COLD FRONT.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. VFR CONDS ARE NOTED AT ALL OUR TAF SITES AS OF 300 PM EXCEPT FOR ACY. ACY/MIV SHOULD CONT TO SEE SOME TEMPO MVFR CIGS FOR THE REST OF THE AFTERNOON...BUT OVERALL CONDS THERE SHOULD BE IMPROVING WITH VFR BY EVENING AND CONTG OVERNIGHT. DRIER/COOLER AIR WILL BE MOVG IN ON NNW WINDS...ESPECIALLY AFTER MIDNIGHT WITH A SECONDARY COLD SURGE AND STRONGER NNW WINDS. THE WINDS ARE EXPECTED TO BECOME GUSTY ON SATURDAY WITH SOME HEATING AND BETTER LOW-LEVEL MIXING OF MOMENTUM. SOME SCATTERED SHOWERS ARE POSSIBLE ON SATURDAY WHICH COULD TEMPORARILY LOWER CIGS/VSBYS TO MVFR...BUT NOT FOR LONG. OUTLOOK... SATURDAY NIGHT AND SUNDAY: VFR, WINDS UNDER 10 KNOTS. SUNDAY NIGHT AND MONDAY: SOME LOWER MVFR CIGS AND VSBYS IN SCATTERED RAIN SHOWERS. SOUTHERLY/SOUTHWESTERLY WINDS UNDER 10 KNOTS SHIFTING TO WEST/NORTHWEST ON MONDAY AND GUSTING TO AROUND 20-25 KNOTS. MONDAY NIGHT AND TUESDAY: VFR, WINDS UNDER 15 KNOTS SHIFTING FROM NORTHWEST TO SOUTHWEST. TUESDAY NIGHT AND WEDNESDAY: POTENTIAL MVFR RESTRICTIONS WITH SCATTERED SHOWERS WITH THE HIGHEST CHANCES AT ABE AND TTN. WIND SHIFT FROM SOUTH/SOUTHWEST TO NORTHWEST ON WEDNESDAY.
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&& .MARINE...
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AS OF MID AFTERNOON...WINDS AND SEAS APPEAR TO BE BELOW SCA CRITERIA ALTHO SEAS AT BUOY 44009 ARE STILL NEAR 5 FT. HWVR...AN SCA REMAINS IN EFFECT FOR COASTAL WATERS...AND WILL GO INTO EFFECT AT MIDNIGHT FOR DEL BAY...AS A SECONDARY SURGE OF COLDER AIR OVERNIGHT WILL PRODUCE INCREASING NW WINDS STARTING OVERNIGHT AND CONTINUING THROUGH SATURDAY. NW WIND GUSTS TO AT LEAST 25 KT ARE EXPECTED ON SATURDAY WITH SEAS BUILDING TO AROUND 5 FT WELL OFFSHORE. SCA CONDS WILL LIKELY CONT INTO SAT NIGHT. OUTLOOK... SATURDAY NIGHT: SCA CONDITIONS CONTINUE WITH NORTHWESTERLY FLOW. SEAS AROUND FIVE FEET WITH GUSTS AROUND AND JUST OVER 25 KNOTS. SUNDAY AND SUNDAY NIGHT: SUB SCA WINDS AND SEAS SUNDAY WHICH INCREASE SUNDAY NIGHT TO SCA CRITERIA BY MONDAY MORNING WITH SOUTHWESTERLY FLOW. MONDAY AND MONDAY NIGHT: SCA SEAS AND WIND GUSTS SHIFTING FROM WEST TO NORTHWEST AND DECREASING BELOW SCA CRITERIA BY MONDAY NIGHT. TUESDAY THROUGH WEDNESDAY: SUB SCA WIND GUSTS AND SEAS.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EDT SUNDAY FOR ANZ430-431.
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&& $$ SYNOPSIS...GAINES NEAR TERM...AMC SHORT TERM...AMC LONG TERM...GAINES AVIATION...AMC/GAINES MARINE...AMC/GAINES

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