Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 120152 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 952 PM EDT FRI JUL 11 2014 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO BUILD ACROSS THE NORTHEAST STATES TONIGHT, THEN PUSH OFFSHORE SATURDAY. A WARM FRONT MAY TRY TO LIFT ACROSS THE AREA SATURDAY NIGHT INTO SUNDAY. A PRE FRONTAL OR LEE SIDE TROUGH WILL DEVELOP ACROSS THE MID ATLANTIC STATES MONDAY INTO TUESDAY, BEFORE A COLD FRONT SWEEPS ACROSS THE AREA TUESDAY INTO EARLY WEDNESDAY. HIGH PRESSURE WILL RETURN TO THE NORTHEAST BY THE END OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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THE SEABREEZE FRONT WAS ABLE TO PUSH ALL THE WAY THROUGH THE PHILLY METRO AREA INTO SOUTHEAST PENNSYLVANIA THIS EVENING. THE FRONT WAS ABLE TO TOUCH OFF SPOTTY SHOWERY ACTIVITY IN AND AROUND THE METRO AREA WHICH ARE QUICKLY DISSIPATING WITH THE LOSS OF HEATING AND FORCING FROM THE FRONT. WE SHOULD REMAIN DRY THROUGH THE OVERNIGHT HOURS. OTHERWISE, SFC HIPRES BUILDS TOWARD THE NEW ENGLAND AND MID- ATLANTIC COAST TONIGHT. THE 12Z NAM INDICATES THE POTENTIAL FOR CLOUDS TO LINGER INTO THE OVERNIGHT ALONG AND EAST OF THE DELAWARE BASED ON HIGH RH VALUES AT 850 MB, BUT THIS MODEL WAS AN OUTLIER AND RH VERIFIED TOO HIGH THIS AFTN BASED ON NEARBY ACARS SOUNDINGS. ACCORDINGLY, A GOOD SETUP FOR RADIATIONAL COOLING IS FORECAST FOR TNGT UNDER CLEARING SKIES AND LIGHT WINDS. LEANED TOWARD THE COOLER MAV GUIDANCE FOR MIN TEMPS TONIGHT. FOG AND/OR STRATUS MAY DEVELOP TOWARD MORNING, ESPECIALLY ALONG THE COAST OF SRN NJ AND DELMARVA WHERE THERE IS MOISTURE POOLING.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... THE HIGH WILL MOVE OFF THE NEW ENGLAND AND MID-ATLANTIC COAST SATURDAY. SOUTHERLY RETURN FLOW AROUND THE HIGH WILL BE LIGHT OVER THE FORECAST AREA SO DO NOT EXPECT A BIG SURGE OF WARM/MOIST AIR BACK INTO THE REGION. LLVL THETA-E RIDGE DOES DRAW NORTHWARD INTO CENTRAL PA, SO DIURNALLY-DRIVEN SHOWERS SHOULD STAY WEST OF THE CWA. UNDER PLENTY OF SUNSHINE, MAX TEMPS ARE IN THE MID TO UPPER 80S EXCEPT COOLER NEAR THE WATERS AND IN THE POCONOS. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... A WET PERIOD CONTINUES TO LOOKS TO BE IN STORE EARLY NEXT WEEK, ALTHOUGH THERE IS SOME DISAGREEMENT BETWEEN OPERATIONAL MODELS AND HOW THEY HANDLE THE SYSTEM. SATURDAY NIGHT IS FORECAST TO BE THE LAST DRY PERIOD IN THE FIRST HALF OF THE LONG TERM FORECAST. THERE MAY BE A WARM FRONT LIFT ACROSS THE AREA OVERNIGHT SATURDAY INTO SUNDAY MORNING, BUT FOR NOW WE WILL KEEP DRY WEATHER ACROSS THE AREA. THEN WE ENTER A PERIOD THROUGH AT LEAST TUESDAY WHEN WE HAVE A CHANCE OF RAIN EACH PERIOD, DAY AND NIGHT. STARTING SUNDAY, A SERIES OF FRONTAL BOUNDARIES WILL BEGIN MOVING OUT OF THE UPPER MISSISSIPPI RIVER VALLEY AND INTO THE MIDWEST. AT THE SAME TIME, A PRE-FRONTAL OR LEE-SIDE TROUGH WILL SET UP ACROSS THE MID-ATLANTIC REGION. THE FRONTAL BOUNDARIES TO OUR WEST WILL SLOW DOWN INTO MONDAY, BEFORE THE INITIAL ONE BEGINS TO TAKE OVER, WHILE THE SURFACE TROUGH ACROSS THE MID-ATLANTIC REMAINS IN PLACE. SEVERAL SHORT WAVE/VORTICITY IMPULSES WILL SWING AROUND THE MID-UPPER LOW ACROSS THE GREAT LAKES REGION THROUGH THE PERIOD, KEEPING HIGH CHANCES OF SHOWERS AND THUNDERSTORMS EACH PERIOD. THE GFS AND ECMWF HAVE SPLIT IN THEIR SOLUTIONS IN REGARDS TO HOW FAST THE FRONT MOVES THROUGH THE AREA. THE GFS IN ITS LATEST MODEL RUN HAS SPEND THE FRONT UP AND MOVED IT THROUGH BY TUESDAY MORNING, WHICH BASICALLY ENDS ALL PRECIPITATION BY TUESDAY. MEANWHILE, THE ECMWF KEEPS THE FRONT SLOWLY MOVING INTO THE AREA AND THROUGH LATE TUESDAY INTO WEDNESDAY MORNING WHICH IS MORE IN LINE WITH PREVIOUS RUNS. FOR NOW WE ARE GOING TO KEEP CLOSER TO WPC/ECMWF SOLUTION AND KEEP AN ENHANCED CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH TUESDAY NIGHT. DURING THE SUNDAY THROUGH TUESDAY PERIOD, THERE WILL BE THE THREAT FOR VERY HEAVY RAINFALL WITH FLOODING POSSIBLE AS PW VALUES WILL BE NEAR OR OVER 2 INCHES. IN ADDITION, WITH THE WARM/UNSTABLE AIRMASS IN PLACE, DEPENDING ON THE MID-UPPER JET DYNAMICS AND FORECAST SHEAR, THERE COULD BE A PERIOD OF STRONG TO SEVERE STORMS. MONDAY AND TUESDAY LOOK TO BE THE PERIOD OF HIGHEST STRONG/SEVERE THREAT. REGARDLESS OF WHICH SOLUTION IS RIGHT, WE EXPECT A DRYING OUT PERIOD STARTING LATE WEDNESDAY INTO THURSDAY AS PW VALUES LOWER TO AN INCH OR LESS ACROSS THE AREA AND HIGH PRESSURE BUILDS BACK ACROSS THE NORTHEAST. HOWEVER, ISOLATED SHOWERS AND THUNDERSTORMS MAY RETURN BY FRIDAY AS RETURN FLOW DEVELOPS AND MOISTURE BEGINS TO CREEP BACK NORTHWARD. AFTER ABOVE NORMAL TEMPERATURES FOR THE FIRST HALF OF THE EXTENDED SUNDAY-TUESDAY, NEAR OR EVEN SLIGHTLY BELOW NORMAL TEMPERATURES COULD RETURN FOR THE SECOND HALF OF NEXT WEEK. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR THRU 06Z. PATCHY FOG POSSIBLE BETWEEN 06Z-12Z AT THE TERMINALS TO THE SOUTH AND WEST OF KPHL. IFR CIGS IN STRATUS ALSO POSSIBLE TOWARD SUNRISE AT ACY/MIV. VFR DURING THE DAYTIME HOURS SATURDAY WITH HIPRES JUST OFFSHORE. OUTLOOK... SATURDAY NIGHT...MOSTLY VFR. SUNDAY-MONDAY...GENERALLY VFR WITH A CHANCE FOR SHOWERS AND THUNDERSTORMS. LOCALLY MVFR/IFR CONDITIONS POSSIBLE WITH SHOWERS OR THUNDERSTORMS. GUSTY AFTERNOON WINDS 15-20 KNOTS. TUESDAY-TUESDAY NIGHT...SHOWERS AND THUNDERSTORMS EXPECTED WITH A COLD FRONTAL PASSAGE. MVFR/IFR CONDITIONS LIKELY WITH SHOWERS OR THUNDERSTORMS. GUSTY WINDS IN THE AFTERNOON AROUND 20 KNOTS, WITH STRONGER WIND GUSTS POSSIBLE WITH THUNDERSTORMS. WEDNESDAY...SHOWERS AND THUNDERSTORMS POSSIBLE IN THE MORNING, THEN CLEARING THROUGH THE DAY.
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&& .MARINE...
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EASTERLY WINDS 5-10 KT BECOMING SOUTH-SOUTHEASTERLY TONIGHT AND SOUTHERLY SATURDAY MORNING AS HIPRES MOVES OFF THE COAST. WINDS WILL BE LIGHT DURING THIS TIME. SOUTHERLY FLOW STRENGTHENS SATURDAY AFTERNOON BUT WILL BE BELOW SCA LEVELS WITH GUSTS AROUND 15 KT. OUTLOOK... SUNDAY-TUESDAY NIGHT...NEAR OR LOWER END SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE THROUGH THE OUTLOOK PERIOD AS SOUTHWEST WINDS INCREASE AHEAD OF AN APPROACHING COLD FRONT AND HIGH PRESSURE REMAINS WELL OFF THE COAST. WEDNESDAY...NEAR SMALL CRAFT POSSIBLE EARLY IN THE DAY WITH GUSTY WINDS BEHIND FRONTAL BOUNDARY, THEN DIMINISHING THROUGH THE DAY.
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&& .TIDES/COASTAL FLOODING... THE HIGH TIDES FRIDAY NIGHT, SATURDAY NIGHT, AND SUNDAY NIGHT MAY APPROACH THE MINOR FLOOD LEVEL ALONG THE ATLANTIC COASTAL AREAS, BUT ARE NOT EXPECTED TO REACH HIGH ENOUGH LEVELS TO REQUIRE A COASTAL FLOOD ADVISORY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...ROBERTSON NEAR TERM...HEAVENER/KLEIN SHORT TERM...KLEIN LONG TERM...ROBERTSON AVIATION...KLEIN/ROBERTSON MARINE...KLEIN/ROBERTSON TIDES/COASTAL FLOODING...ROBERTSON

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