Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300959 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 559 AM EDT TUE SEP 30 2014 .SYNOPSIS... A LOW PRESSURE SYSTEM AND WEAK FRONT WILL AFFECT THE WEATHER TODAY AND TONIGHT. HIGH PRESSURE WILL BUILD IN WEDNESDAY AND REMAIN THROUGH FRIDAY. A STRONG COLD FRONT WILL CROSS THE REGION FRIDAY NIGHT INTO EARLY SATURDAY. HIGH PRESSURE WILL BUILD ACROSS THE AREA SATURDAY NIGHT INTO EARLY MONDAY. LOW PRESSURE WILL APPROACH FOR LATER MONDAY AND INTO NEXT TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THROUGH 8 AM...LIGHT SHOWERS NOW APPEAR TO BE CONFINED TO PORTIONS OF NE MD...DE AND FAR SW NJ AS THE CORE OF THE UPPER LEVEL SHORT WAVE PRODUCES MID LEVEL SPRINKLES OR LIGHT SHOWERS. THE 545 AM UPDATE ATTEMPTS TO ACCOUNT FOR THIS SHORT PERIOD LEFTOVERS. OTHERWISE...THICK FOG ALONG MD`S E SHORE AND PORTIONS OF E PA W AND NW OF PHL AS WELL AS FAR NW NJ WILL BEGIN THINNING AROUND 730 OR 8 AM. AN SPS HIGHLIGHTS THAT DIFFICULTY. TODAY...BETWEEN SHORT WAVES IT SHOULD BE QUIET THROUGH EARLY AFTERNOON WITH SOME SUNSHINE VSBY AT TIMES THROUGH THE CLOUDS. AFTERNOON HEATING DEVELOPS SMALL SHOWERS NW OF I95 WHICH PROBABLY HAVE A TENDENCY TO DRIFT WEST. IF THERE IS TO BE ANY THUNDER THIS FAR EAST...IT SHOULD BE CONFINED TO THE FAR WESTERN EDGE OF OUR FCST AREA WESTERN BERKS INTO THE POCONOS. THE ECMWF SUGGESTS TEMPS MAY RUN 1-2F WARMER THAN OUR FCST...ESP E MD. OVERALL: TEMPS ABOUT 7F WARMER THAN NORMAL AND THE ENTIRE MONTH OF SEPTEMBER SHOULD AVERAGE ABOUT 1.5 DEGREES ABOVE NORMAL MOST AREAS. FCST WAS BASED ON A 50 50 BLEND OF THE 00Z/30 GFS/NAM MOS GUIDANCE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... TONIGHT...COOL POOL ALOFT SLIDES EASTWARD ACROSS THE REGION WITH 500MB TEMPS NEAR -15-16C. BANDS OF SHOWERS MAY BE OCCURRING WITH SUBTLE LIFT FROM BOTH WEAK BUT DEEP ELY MOIST WINDS NORTH OF I78 AND THE BACKDOOR COOL FRONT CONVERGENCE ZONE DRIVEN BY THE STRENGTHENING NE FLOW NE OF THE BACKDOOR CF. ADDITIONALLY FOG IS LIKELY TO DEVELOP IN THE COOLER BL AIR NE OF THE FRONTAL BOUNDARY. TEMPS ABOUT 10F WARMER THAN NORMAL. FCST WAS BASED ON A 50 50 BLEND OF THE 00Z/30 GFS/NAM MOS GUIDANCE. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... THE LAST OF THE UPPER LOW AND WEAK SFC LOW WILL BE EXITING THE AREA WEDNESDAY. THERE WILL STILL BE ENOUGH RESIDUAL LOW LEVEL MOISTURE TO PRODUCE SOME SCT SHOWERS...MOSTLY DURING THE FIRST PART OF THE DAY. WE HAVE RETAINED THE CHC POPS FROM EARLIER. THE POPS DECREASE DURING THE AFTERNOON FROM W TO E. TEMPERATURES WED NEAR OR A BIT ABOVE NORMAL...MOSTLY LOW/MID 70S. WED NIGHT THRU FRI MORNING...MOSTLY DRY WEATHER DURING THIS PERIOD AS HIGH PRESSURE BUILDS ACROSS THE AREA. PARTLY TO MOSTLY SUNNY DAYTIME PERIODS AND MOSTLY CLR OVERNIGHTS. TEMPERATURES AGAIN...NEAR OR A BIT ABOVE NORMAL. FRI AFTERNOON THRU SATURDAY...A STRONG COLD FRONT WILL CROSS THE AREA FRI NIGHT INTO EARLY SAT. THE MODELS HAVE BEEN RATHER CONSISTENT WITH A 6 HR OR SO WINDOW OF QPF CENTERED AROUND FRI EVENING. WE HAVE UPPER THE POPS TO LIKELY FOR THE EVENING PERIOD WITH THE EXTRA CONFID IN MULTIPLE/CONSISTENT TRENDS. PROBABILITIES FOR THUNDER LOOK LOW AT THIS POINT SO WE WILL HOLD ON THAT...SOME GUSTY WINDS WILL ACCOMPANY THE FROPA HOWEVER. TEMPS WILL DROP BACK TO BELOW NORMAL SAT WITH DECENT COLD ADVECTION EXPECTED AFTER FROPA. SAT NIGHT THRU MONDAY...ANOTHER DRY PERIOD EXPECTED WITH HIGH PRESSURE BUILDING IN, TEMPERATURES WILL BE BELOW NORMAL SUNDAY...BUT BACK TO NEAR NORMAL MONDAY. LOWS BOTH SAT AND SUN NIGHTS WILL FEATURE LOW 40S NORTH RANGING TO THE LOW 50S OVER THE DELMARVA AND METRO PHILADELPHIA. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THROUGH 12Z...AREAS OF LIGHT RAIN SHOWERS FROM MID LEVEL DECK OF CIGS AOA 10000 FT VCNTY N DE AND NE MD AT 10Z SHOULD FINALLY WEAKEN AND DRY OUT AROUND 12-13Z AS THE UPPER LEVEL CORE OF THE MID LEVEL SHORT WAVE DRIFTS EASTWARD ONTO THE COAST. LIGHT SOUTH WIND WITH HIGHER THAN MODELED DEWPOINTS SHOULD FACILITATE THE DEVELOPMENT OF 3 MI FOG PATCHES AND EVEN BRIEF LIFR CONDITIONS IN ST/FOG MAINLY VCNTY KRDG/KABE. AFTER 12Z...AFTER ANY LEFTOVER IFR ST/FOG BURNS OFF BY 14Z...OTHERWISE SCT-BKN CLOUDS AOA 5000 FT WITH A POSSIBLE SHOWER VCNTY KRDG/KABE LATE IN THE DAY. LIGHT SOUTH WIND TURNING E. TONIGHT...WIND BECOMING NE AT 5-15 KT AND A DECK OF IFR ST/FOG SHOULD DEVELOP SOUTHWESTWARD FROM LONG ISLAND BEHIND THE BACKDOOR COLD FRONT CURRENTLY MOVING SW FROM SOUTHERN NEW ENGLAND. CHANCE OF SHOWERS...MAINLY N OF KPHL. OUTLOOK... WEDNESDAY...MOSTLY VFR. SCT SHOWERS WITH SHORT PERIODS OF MVFR CONDITIONS POSSIBLE. E/NE WINDS WITH GUSTS UP TO 15 KNOTS. THURSDAY...MORNING FOG WITH LOCAL LOWER CIGS/VSBYS...THEN MOSTLY VFR. N WIND GUST 15 KT...BECOMING NE LATE. FRIDAY...VFR CIGS EXCEPT POSSIBLE MVFR CONDITIONS IN ST/FOG EARLY FRIDAY MORNING AND THEN AGAIN FRIDAY NIGHT IN SHOWERS NEAR A COLD FRONT. E-SE WIND BECOMING S OR SW LATE AT NIGHT. SATURDAY...A FEW MORNING SHOWERS EAST...THEN VFR CONDITIONS EXPECTED. && .MARINE... NO HEADLINES ATTM. TODAY...LIGHT WINDS AND SEAS AOB 3 FT TODAY WITH THE S-SW WIND TURNING TO THE EAST OR NORTHEAST. TONIGHT...NE WINDS INCREASING WITH GUSTS TO 22 KT LATE AND SEAS BUILDING TO NEAR 4 FT BY SUNRISE WEDNESDAY. CAPPED SEAS AT 4 FT THROUGH 8AM WEDNESDAY AS I BELIEVE THE GFS WW3 GUIDANCE IS TOO SOON TOO HIGH. OUTLOOK... WEDNESDAY THRU WED NIGHT: NE FLOW WITH BUILDING WINDS AND SEAS AND SCA CRITERIA EXPECTED ALONG THE NNJ COAST AND THEN POSSIBLY SOUTHWARD TO THE ENTIRE ATLANTIC COAST LATER WEDNESDAY OR WEDNESDAY NIGHT. DELAWARE BAY MAY NOT SEE WIND GUSTS ABOVE 22 KT WITH ANY SCA HEADLINE THERE NOT LIKELY. HAVE HELD OFF ON ISSUING ANY FORMAL HEADLINES ON THIS FORECAST UPDATE AS CONDITIONS WILL JUST MEET LOWER END SCA CRITERIA AND CONFIDENCE IS NOT YET HIGH. THURSDAY...SMALL CHANCE OF A CONTINUING SCA FLAG SEAS ON THE ATLANTIC WATERS FROM NE SWELLS GENERATED BY AN OFFSHORE LOW. CONDITIONS MAY DROP BELOW SCA CRITERIA LATE. FRIDAY...SOUTH WINDS INCREASING AND BUILDING SEAS. SCA CONDITIONS A GOOD BET BY AFTERNOON. SHOWERS WITH GUSTY WINDS LATE. SATURDAY...SCA CONDITIONS EARLY WITH SCT SHOWERS...THEN WINDS AND SEAS DIMINISHING LATE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...O`HARA NEAR TERM...DRAG 558 SHORT TERM...DRAG LONG TERM...O`HARA AVIATION...DRAG/O`HARA 558 MARINE...DRAG/O`HARA 558

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