Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300305 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1105 PM EDT MON SEP 29 2014 .SYNOPSIS...
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LOW PRESSURE OVER THE EASTERN GREAT LAKES TONIGHT WILL MOVE ACROSS PENNSYLVANIA TUESDAY WHILE A WEAK BACKDOOR COLD FRONT OVER SOUTHERN NEW ENGLAND SLIDES SOUTHWEST ACROSS THE REGION. THAT LOW PRESSURE SYSTEM WILL DEVELOP OUT TO SEA WEDNESDAY WITH HIGH PRESSURE IN EASTERN CANADA RIDGING DOWN INTO THE MID ATLANTIC STATES THURSDAY. A STRONGER COLD FRONT WILL MOVE EAST ACROSS THE MID ATLANTIC STATES EARLY SATURDAY. WEAK HIGH PRESSURE FOLLOWS NEXT SUNDAY. A WARM FRONT APPROACHES THE REGION EARLY NEXT WEEK.
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&& .NEAR TERM /THROUGH TUESDAY/...
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1040 PM UPDATE...RAISED POPS ON PORTIONS OF THE DELMARVA AND COASTAL NJ THROUGH ABOUT 07Z AND LOWERED POPS NE PA AND NW NJ. TOO MUCH RAIN ON RADAR. THEN THE CONCERN...SINCE DEWPOINTS ARE MUCH HIGHER THAN MODELED...HOW EXTENSIVE THE FOG AT SUNRISE TUESDAY. COULD SEE PATCH DENSE DEVELOP PORTIONS OF E PA WHERE IT CLEARS BY 09Z AND THEN SEPARATELY OVER COASTAL SECTIONS. TUESDAY...A QUIET MORNING EXPECTED...THEN SCT SHOWERS SHOULD DEVELOP DURING THE MID-LATE AFTN E PA PER INCREASING INSTABILITY ALOFT AS 500MB TEMPS COOL 2C LATE IN THE DAY STEEPENING MID LVL LAPSE RATES.
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&& .SHORT TERM /TUESDAY NIGHT/...
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TUESDAY NIGHT...COOL POOL ALOFT SLIDES EWD ACROSS THE REGION WITH 500MB TEMPS NEAR -15-16C. BANDS OF SHOWERS MAY BE OCCURRING WITH SUBTLE LIFT FROM BOTH WEAK ELY WINDS NORTH OF I78 AND THE BACKDOOR COOL FRONT CONVERGENCE ZONE DRIVEN BY THE STRENGTHENING NE FLOW NE OF THE BACKDOOR CF. ADDITIONALLY FOG MAY DEVELOP IN THE COOLER BL AIR NE OF THE FRONTAL BOUNDARY.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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VERY FEW CHANGES IN THE EXTENDED PERIOD FORECAST FROM 12 HOURS AGO. SEVERAL CHANCES FOR RAIN THROUGH THIS TIME PERIOD BUT AMOUNTS LOOK LIKE THEY WILL BE ON THE RELATIVELY LIGHT SIDE. TEMPERATURES FOR THE TIME PERIOD WILL BE SLIGHTLY ABOVE NORMAL EARLY IN THE PERIOD, THEN TRENDING TO NEAR NORMAL LATE IN THE PERIOD. HIGH PRESSURE BUILDS INTO THE REGION FOR LATE WEDNESDAY INTO FRIDAY. COLD FRONTAL BOUNDARY APPROACHING WITH NEXT UPPER LEVEL SYSTEM MOVES THROUGH LATE FRIDAY/EARLY SATURDAY BRINGING ANOTHER CHANCE OF RAIN. HIGHEST POPS THROUGH THE LONG TERM PERIOD ARE ASSOCIATED WITH THIS SYSTEM. HIGH PRESSURE BUILDS IN ONCE AGAIN FOR THE REMAINDER OF THE WEEKEND BEFORE A WARM FRONTAL BOUNDARY APPROACHES FROM THE SOUTHWEST LATE ON MONDAY, ONCE AGAIN BRINGING A CHANCE OF PRECIPITATION. USE WPC GUIDANCE PREDOMINATELY FOR DAYS 4 THOUGH 7. FOR TUE NIGHT INTO THU, USED A 50/50 BLEND OF PREVIOUS FORECAST AND ADJUSTED GFS MAV MOS
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&& .AVIATION /03Z TUESDAY THROUGH SATURDAY/...
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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 LVL DECK OF CIGS AOA 6000 FT WITH A CLEARING TREND EXPECTED E PA OVERNIGHT. LIGHT SOUTH WIND WITH HIGHER THAN MODELED DEWPOINTS SHOULD FACILITATE THE DEVELOPMENT OF 1-3 MI FOG PATCHES AND POTENTIAL BRIEF LIFR CONDS BOTH VCNTY KRDG/KABE BUT ALSO ELSEWHERE WHERE IT RAINED THIS PAST MONDAY AFTERNOON/EVENING. AFTER 12Z TUESDAY...AFTER ANY LEFTOVER IFR ST/FOG BURNS OFF BY 14Z....SCT CLOUDS AOA 5000 FT BECOME BKN MID-LATE AFTN WITH A POSSIBLE SHOWER VCNTY KRDG/KABE. LIGHT SOUTH WIND TURNING E. TUESDAY NIGHT...WIND BECOMING NE AT 5-15 KT AND A DECK OF IFR ST/FOG SHOULD DEVELOP BEHIND THE BACKDOOR COLD FRONT CURRENTLY MOVING SW FROM SOUTHERN NEW ENGLAND. CHC OF SHOWERS...MAINLY N OF KPHL. OUTLOOK... WEDNESDAY...MAINLY VFR CIGS WITH POSSIBLE MVFR CONDS IN SHOWERS KABE/KRDG/KTTN DURING THE MORNING. E/NE WINDS GUST 15 KNOTS. THURSDAY...POSSIBLE MVFR FOG EARLY OTHERWISE VFR SCT-BKN CLOUDS AOA 4000 FT. N-NW WIND GUST 15 KT. FRIDAY...VFR CIGS EXCEPT POSSIBLE MVFR CONDS 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...VFR CONDITIONS EXPECTED.
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&& .MARINE...
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SEAS THIS EVENING ARE AROUND TWO FEET ACROSS THE REGION. WINDS WILL BE LIGHT THROUGH TONIGHT AS WELL. TOMORROW WE WILL GRADUALLY SEE SEAS BUILD AND WINDS INCREASE OUT OF NORTHEAST. SEAS MAY REACH FOUR FEET TUESDAY AFTERNOON WITH SOME WIND GUSTS AROUND 20 KNOTS AS WELL. CONDITIONS BELOW SCA CRITERIA FOR THIS PERIOD. TUESDAY NIGHT...NE WIND 10-20 KT WITH ATLC SEAS NEAR 4 FT. NO HEADLINE ANTICIPATED ATTM. OUTLOOK... WEDNESDAY THROUGH WEDNESDAY NIGHT: NE FLOW WEDNESDAY AND WEDNESDAY NIGHT SHOULD INCREASE TO SCA CRITERIA ALONG THE NNJ COAST AND THEN POSSIBLY SOUTHWARD TO THE ENTIRE ATLC 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 SCA SEAS ON THE ATLANTIC WATERS FROM NE SWELLS GENERATED BY AN OFFSHORE LOW. FRIDAY...WIND BECOMING SOUTH BY NIGHT. SMALL CHANCE OF AN SCA AT NIGHT. SATURDAY...SCA CONDITIONS POSSIBLE EARLY WITH COLD FRONT PASSAGE, THEN IMPROVING CONDITIONS EXPECTED.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG/SZATKOWSKI 1104 NEAR TERM...DRAG/GAINES/HEAVENER/JOHNSON 1104 SHORT TERM...DRAG/GAINES/HEAVENER 1104 LONG TERM...SZATKOWSKI AVIATION...DRAG/GAINES/SZATKOWSKI/HEAVENER/JOHNSON 1104 MARINE...DRAG/GAINES/SZATKOWSKI/HEAVENER 1104

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