Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 280820 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 420 AM EDT SUN SEP 28 2014 .SYNOPSIS... HIGH PRESSURE OVER THE AREA WEAKENS TONIGHT AND MONDAY. A BACKDOOR COLD FRONT IS EXPECTED TO MOVE SOUTH ACROSS THE AREA TUESDAY. FOR MIDWEEK, HIGH PRESSURE IS FORECAST TO STRENGTHEN ACROSS EASTERN CANADA, WHILE WEAK LOW PRESSURE EAST OF THE CAROLINAS MOVES SLOWLY NORTHEAST THROUGH THURSDAY. A COLD FRONT EXTENDING SOUTH ACROSS THE GREAT LAKES AND OHIO VALLEY FRIDAY SHOULD CROSS OUR REGION SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HIGH PRESSURE WILL REMAIN ACROSS THE AREA TODAY. AFTER SOME PATCHY MORNING FOG LIFTS...SKIES WILL BE MOSTLY SUNNY FOR THE BALANCE OF THE DAY. SOME HIGH CLOUDS MAY CROSS THE AREA...BUT THIS WILL DO LITTLE TO KEEP TEMPERATURES FROM RISING INTO THE UPPER 70S TO LOW 80S ACROSS THE REGION. THESE TEMPERATURES ARE ABOUT 10 DEGREES ABOVE NORMAL FOR LATE SEPTEMBER. WINDS WILL BE LIGHT TODAY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... THE HIGH WILL BEGIN TO WEAKEN ACROSS THE AREA...BUT STILL FAIR WEATHER IS EXPECTED. AGAIN...MORE PATCHY OVERNIGHT FOG WILL DEVELOP AFTER MIDNIGHT. LOW TEMPERATURES WILL BE SOMEWHAT MILD FOR LATE SEPTEMBER...BEING IN THE UPPER 50S TO LOW 60S IN MANY AREAS. WINDS WILL BE LIGHT. && .LONG TERM /MONDAY THROUGH SATURDAY/... 500 MB: A COUPLE OF SHORT WAVES MOVE THROUGH THE MID AND NORTH ATLANTIC STATES MONDAY THROUGH WEDNESDAY AND BECOME BETTER ORGANIZED SOUTHEAST OF NEW ENGLAND THURSDAY AND FRIDAY. THEREAFTER A LARGE AMPLITUDE TROUGH IN CENTRAL NORTH AMERICA NEXT WEEKEND EDGES EAST. TEMPERATURES: SEPTEMBER WILL END UP AT LEAST A DEGREE ABOVE NORMAL AS CALENDAR DAY AVERAGE TEMPERATURES ARE FORECAST TO BE ABOUT 10 DEGREES ABOVE NORMAL MONDAY AND 5 TO 8 DEGREES ABOVE NORMAL TUESDAY THROUGH FRIDAY BEFORE COOLING CLOSER TO NORMAL DURING NEXT WEEKEND. FORECAST BASIS: UNLESS OTHERWISE NOTED THE LONG TERM PERIOD OF THIS FORECAST IS GENERALLY BASED ON A 50 50 BLEND OF THE 00Z/28 NAM/GFS MOS FOR THE PERIOD MONDAY-TUESDAY...THE 00Z/28 GFS MOS TUESDAY NIGHT-WEDNESDAY...THEN THEREAFTER (WEDNESDAY NIGHT ONWARD) THE 0643Z/28 WPC GRIDDED GUIDANCE WHICH AT TIMES IS BLENDED 50 50 WITH THE 00Z/28 MEXMOS. ALL THIS IS EVENTUALLY CHECKED AGAINST THE 00Z/28 ECMWF TO SEE IF WE`RE IN THE BALLPARK WITH ECMWF CYCLICALLY PERSISTENT 18Z 2 METER TEMPERATURES. PRECIPITATION PROBABILITY GUIDANCE IS CHECKED AGAINST THE 21Z/27 SREF 3HRLY POPS FOR .01 THROUGH 00Z SATURDAY AND THEREAFTER THE 00Z/28 GEFS 6HR POPS FOR 0.05. THE DAILIES... MONDAY-WEDNESDAY...VARIABLE CLOUDINESS (IN PART INSTABILITY DRIVEN) WITH PROBABLY A BAND OR 2 OF SHOWERS AS SHORT WAVES PASS THROUGH THE REGION. THE MOSTLY LIKELY TIME FOR SHOWER OCCURRENCE IS TUESDAY AFTERNOON-WEDNESDAY. THUNDER IS POSSIBLE (NOT GRIDDED INTO THE FCST YET) WITH SUBZERO SWI AND TT NEAR 52...MAINLY E PA. MODELS ARE WAFFLING AND SO CONFIDENCE ON DETAILS ARE STILL WELL BELOW AVERAGE. ON THIS 00Z/28 CYCLE...ECMWF/GFS/NAM ARE ALL MORE DEFINED...POTENT. THERE IS STILL ROOM IN THE MODELS FOR STRENGTHENING THIS SYSTEM CLOSER TO THE COAST OR DEVELOPING A SEPARATE SFC LOW (NO LINK TO THE CAROLINAS SFC LOW) OVER NORTHERN PA...BENEATH THE DEVELOPING CIRCULATION ALOFT AND THEN REDEVELOPING THIS N PA SFC WAVE JUST S OF LONG ISLAND ON WEDNESDAY. SO THE FORECAST HAS FOCUSED POPS LATE TUE-WED. THESE POPS ARE STILL CONSERVATIVE DUE TO UNCERTAINTY BUT HAVE TO BELIEVE THAT THERE WILL BE A BAND OF MEASURABLE RAIN BETWEEN .01 AND .75 INCHES MOVING EWD ACROSS THE I78 REGION NORTHWARD LATE TUE INTO WEDNESDAY. THIS IS OVER AN AREA THAT DEFINITELY HAS SEEN A SHORTFALL OF RFALL THIS YEAR. AGAIN UNCERTAINTY AS OF THIS WRITING. THE IMPACT OF TUESDAYS BACKDOOR COLD FRONT APPEARS TO BE DELAYED 12-18 HOURS UNTIL TUE NIGHT-WED. THEREFORE...OUR 330 AM FORECAST HAS WARMER TEMPERATURES FOR TUESDAY THAN OUR COOLER PRIOR FORECAST. THURSDAY-FRIDAY...WEAKENING NORTHEAST FLOW AND PROBABLY DRY AS THE RIDGE ALOFT BUILDS INTO THE AREA FROM THE WEST BEHIND THE DEVELOPING NW ATLC CYCLONIC CIRCULATION. NEXT WEEKEND...A COLD FRONTAL PASSAGE IS EXPECTED WITH PROBABLY A BAND OF SHOWERS FRIDAY NIGHT OR SATURDAY THEN PROBABLY A DRIER SUNDAY. TIDES: A 1 FOOT OR GREATER ONSHORE FLOW POSITIVE DEPARTURE SURGE WILL BE DEVELOPING FOR MID AND LATE WEEK. RIGHT NOW NO THREAT FOR MINOR CF. IF THE LOW PRESSURE SYSTEM DEVELOPS CLOSER TO THE COAST WE COULD HAVE A LITTLE MORE CONCERN. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. ANOTHER FINE FLYING WEATHER DAY EXPECTED ACROSS THE REGION. THERE WILL BE PATCHY FOG ACROSS THE AREA WITH LOCALLY LOW VSBYS EARLY THIS MORNING...BUT AFTER THAT MOSTLY CLR SKIES AND LIGHT WINDS. SOME CI CLOUDS WILL MOVE ACROSS THE AREA THIS MORNING. WINDS WILL BE 5 TO 8 KTS THIS AFTERNOON...MOSTLY FROM TH W OR SW. VFR TONIGHT WITH AGAIN PATCHY FOG OVERNIGHT. OUTLOOK... MONDAY THROUGH TUESDAY...MAINLY VFR CIGS AOA 10000 FT MONDAY AND AOA 4000 FT TUESDAY. POSSIBLE SUB-VFR VSBYS LATE MONDAY NIGHT OR TUESDAY IN A FEW SHOWERS OR STRATUS/FOG. LIGHT SOUTHWEST WIND MONDAY BECOME EASTERLY TUESDAY. SMALL CHC ISOLATED THUNDER E PA LATE TUE. WEDNESDAY THROUGH THURSDAY...VFR CIGS WITH A CHANCE FOR PERIODS OF MVFR CONDS IN SHOWERS...ESPECIALLY WEDNESDAY AND ESPECIALLY KABE/KRDG. NE WIND GUST 15-20 KT. && .MARINE... PLEASANT CONDITIONS EXPECTED ON THE WATERS TODAY AND TONIGHT. HIGH PRESSURE WILL MOVE EAST TONIGHT. WINDS WILL BE MOSTLY UNDER 10 KNOTS WITH DIRECTIONS VARIABLE THIS MORNING...THEN SRLY OR SERLY THIS AFTERNOON AND TONIGHT. WAVES 2 TO 3 FT ON THE OCEAN AND 1 TO 2 FT ACROSS DEL BAY. OUTLOOK... MONDAY...NO MARINE HEADLINE WITH A LIGHT SOUTHWEST WIND SHIFTING E LATE MONDAY NIGHT. TUESDAY THROUGH THURSDAY...WINDS AND SEAS ARE EXPECTED TO REACH SMALL CRAFT ADVISORY LEVELS SOMETIME DURING TUESDAY OR TUESDAY NIGHT. SCA CONDITIONS ONCE DEVELOPED WILL LIKELY LAST THROUGH AT LEAST THURSDAY AS LOW PRESSURE DEVELOPS SOMEWHERE OFF THE MID ATLC COAST. THE TRACK AND ORGANIZATION OF THIS SYSTEM IS STILL UNCERTAIN AT THIS TIME. HAZARDOUS SEAS OF 5 FT OR GREATER ON THE ATLANTIC WATERS MAY LINGER THROUGH FRIDAY OR SATURDAY. && .CLIMATE... RERMPO YDY..EQUALED RECORD MAX. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG NEAR TERM...O`HARA SHORT TERM...O`HARA LONG TERM...DRAG 319 AVIATION...DRAG/O`HARA 319 MARINE...DRAG/O`HARA 319 CLIMATE...

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