Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 190155 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 955 PM EDT MON AUG 18 2014 .SYNOPSIS... A STALLED FRONTAL BOUNDARY OVER VIRGINIA WILL BE A CONDUIT FOR A WAVE OF LOW PRESSURE THAT WILL TRACK ALONG IT AND MOVE OFFSHORE TUESDAY. THE FRONTAL BOUNDARY SHOULD REMAIN NEARLY STATIONARY FROM THE GREAT LAKES TO THE SOUTHERN MID-ATLANTIC STATES WEDNESDAY AND THURSDAY WHILE A SERIES OF DISTURBANCES RIDE ALONG IT. THE FRONT WILL GRADUALLY SHIFT FARTHER SOUTH AND WEST OF THE AREA FRIDAY AND SATURDAY AS HIGH PRESSURE WEDGES DOWN FROM EASTERN CANADA. THIS HIGH PRESSURE SYSTEM SHOULD REMAIN NEARLY STATIONARY OVER NEW ENGLAND AND THE CANADIAN MARITIMES ON SUNDAY AND MONDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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WEAK LOW PRESSURE WILL MOVE FROM NORTH CENTRAL NORTH CAROLINA TO THE LOWER CHESAPEAKE BAY REGION DURING THE NIGHT. THE NORTHERN EDGE OF THE CLOUDS ASSOCIATED WITH THE LOW SHOULD REMAIN ACROSS THE CENTRAL PART OF OUR FORECAST AREA DURING THE NIGHT. SOME LIGHT RAIN SHOWERS MAY REACH AREAS AS FAR NORTH AS A CHESTERTOWN TO DOVER TO CAPE MAY LINE. LOWS ARE FORECAST TO BE MAINLY IN THE 50S UP NORTH AND IN THE 60S IN THE SOUTH.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
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LOW PRESSURE WILL CONTINUE TO MOVE SOUTHEAST OFF THE MID-ATLANTIC COASTLINE ON TUESDAY. GOOD MODEL CONSENSUS SHOWING CLOUDS WILL BE ON THE DECREASE BY THE AFTERNOON WITH THE SLIGHT RAIN CHANCES DIMINISHING BY EARLY AFTERNOON ACROSS THE SOUTH. EXPECTED CLOUD COVER MAY KEEP TEMPERATURES IN THE MID 80`S ACROSS THE SOUTH, A FEW DEGREES COOLER THAN MAV/MET GUIDANCE. MAV/MET BLEND LOOKED REASONABLE ACROSS THE REMAINDER OF THE REGION WITH HIGH TEMPERATURES. VERY LIGHT QPF AGAIN AS SHOWN ON THE MAJORITY OF OPERATIONAL MODEL RUNS AND WPC GUIDANCE ACROSS THE SOUTH, SREF OVERDONE.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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THE GFS INITIALIZATION LOOKED SLIGHTLY BETTER THAN THE WRF-NMMB, ESPECIALLY WITH THE THERMAL FIELDS. THAT BEING SAID, THE RUN TO RUN AND MODEL TO MODEL CONTINUITY IN THE LONG RANGE HAS BEEN LESS THAN DESIRABLE. THE TREND WE HAVE SEEN SINCE LAST WEEK IS A SOUTHWARD SUPPRESSION TO SYSTEMS. DP/DT ON TONIGHT`S SYSTEM FOR OUR CWA IS A MERE SHELL OF WHAT IT ONCE WAS AND NOW WE ARE SEEING THE START OF THE UNRAVELING WITH THE WEDNESDAY INTO THURSDAY SYSTEM. AS WAS MENTIONED YESTERDAY BY MY CO-AUTHOR, MODEL TENDENCY IS TO UNDO REX BLOCKS TOO QUICKLY. EVEN IF ITS NOT TEXT BOOK REXY, ITS REXY ENOUGH FOR US. WE ARE GOING TO GIVE THE DOMED PROTECTION OF THE NEW ENGLAND AND CANADIAN MARITIME HI PRES MORE DUE. THIS HAS THE LOOKS OF A SEPTEMBER BLOCKING PATTERN. WHILE WE CAN SEE THE KICKER LOW`S IMPACT IN OUR CWA TO BE LESS, NOT CONFIDENT ABOUT ITS FASTER TIMING OFF THE 12Z MODEL RUNS (ENSEMBLES NOT MUCH HELP, AGREE WITH THEIR OP). WE SHAVED THE POP RUBBER BAND BACK, BUT THE PROLONGED INCLUSION OF POPS WEDNESDAY NIGHT INTO FRIDAY IS LIKELY TOO LONG. IN ADDITION, THE STABILIZING INFLUENCE OF THE NEARBY HI PRES IS REDUCING THE CHANCES FOR BOTH HEAVY RAIN AND STRONG/SEVERE STORMS AS THIS IMPULSE SLIDES BY. AGREE WITH THE MID SHIFT ABOUT NO DISTINCT HAZARDOUS WEATHER THREAT FOR THE LONG TERM. WITH THE LOW PRESSURE SYSTEM MOVING OFFSHORE, IN ITS WAKE HIGH PRESSURE "BUILDS" OVER THE NORTHEAST. WHILE THE FLOW CONTINUES TO BE ONSHORE, THE MODEL PREDICTED SUB 925MB MOISTURE REMAINS RATHER DRY. THE TREND IS DRIER VS THE 00Z MODEL SUITE, BUT STILL FEEL A BIT UNCOMFORTABLE. WE WENT WITH CLEAR(ER) SKIES, BUT NOT AS CONFIDENT NEAR THE COAST. WITH CLEAR(ER) SKIES, WE EDGED MIN TEMPS LOWER, STILL ABOVE STAT GUIDANCE BY A COUPLE OF DEGREES. MODEL UNANIMITY NOW ABOUT A DRY DAY ON WEDNESDAY. PRECIPITATION WITH THE APPROACHING KICKER SYSTEM IS NOT EXPECTED TO ARRIVE BY NIGHTFALL. OUR CONVECTIVE TEMPS ARE EITHER PREDICTED TO BE BEYOND REACH OR WE ARE TOO STABLE TO SUPPORT HOME GROWN CONVECTION. IN ESSENCE, WE PUSHED BACK OUR POP/WEATHER GRIDS BY ABOUT 12 HOURS. SOME CLOUDINESS OVER THE TOP OF THE RIDGE AND ONSHORE FLOW MOISTURE SHOULD GENERATE SOME AFTERNOON CLOUDS, SO MAX TEMPS WERE NOT FAR FROM STAT GUIDANCE WHICH LOOKS CONSERVATIVE VS THERMAL FIELDS. WEDNESDAY NIGHT MIGHT ALSO BE DRY, BUT THERE IS A MODELING SPLIT AS TO WHETHER ANY RESIDUAL SHOWERS (NOT PREDICTED TO BE UNSTABLE ENOUGH FOR THUNDER) CAN MAKE IT. THE SLOWING TIMING SWITCH FROM THE NIGHT RUN MODELS IS TOO MUCH TO ACCEPT AND WE KEPT IN A CHANCE. THURSDAY AND THURSDAY NIGHT REMAIN THE GO TO PERIOD, BUT NOT AS BOISTEROUS AS IT LOOKED YESTERDAY. STABILITY IS STILL PREDICTED TO BE ACROSS THE NERN PART OF OUR CWA AS ANY SURFACE WAVE AND THE CLOSED LOW ALOFT GETS SHEARED TO THE SOUTH OF NYC. WHILE THIS KICKER LOW WAS STARTING FARTHER TO THE NORTH, ITS PREDICTED TO UNDERGO A SIMILAR PROCESS TO TONIGHT`S SYSTEM IN WEAKENING WITH TIME. SO WE KEPT POPS IN AND MENTION OF THUNDER WHERE MODELS HAD CONSENSUS ABOUT INSTABILITY ALOFT. POPS WERE KEPT IN FOR FRIDAY BASED ON THE SLOWER TIMING THAT THE 00Z MODELS HAD AND CYCLONIC FLOW ALOFT. FOR THE REST OF THE LONG TERM, MORE BLOCKING IS PREDICTED TO FORM OVER EASTERN CANADA. THIS KEEPS A HIGH PRESSURE RIDGE ANCHORED FROM THE CANADIAN MARITIMES SOUTHWEST INTO OUR CWA WITH AN OFFSHORE SFC LOW FORMING. WHILE THIS LOOKS PRIMARILY DRY, THE ONSHORE FLOW MAY BRING CLOUDINESS INTO OUR CWA PENDING ON THE ORIENTATION OF THE RIDGE AXIS. TEMPERATURES SHOULD AVERAGE BELOW NORMAL THROUGH THE BACK END OF THE LONG TERM.
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&& .AVIATION /02Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A LIGHT AND VARIABLE WIND OVERNIGHT SHOULD SETTLE INTO THE NORTHEAST AND EAST ON TUESDAY MORNING AT SPEEDS OF 5 TO 10 KNOTS. THE WIND MAY VEER TOWARD THE SOUTHEAST ON TUESDAY AFTERNOON. OUTLOOK... TUESDAY NIGHT AND WEDNESDAY...CHANCE OF SOME MVFR CIGS SERN AIRPORTS AND TERMINALS LATE AT NIGHT AND WED MORNING. CONFIDENCE NOT HIGH. PRIMARILY VFR ELSEWHERE. WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...CHANCE FOR SHRA/TSRA AS A SERIES OF DISTURBANCES MOVE THRU THE REGION. LOCAL/TEMPORARY FLIGHT MVFR RESTRICTIONS POSSIBLE. FRIDAY THROUGH SATURDAY...PREDOMINATELY VFR CONDITIONS.
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&& .MARINE...
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NO SCA HAZARDS EXPECTED THROUGH TUESDAY. SEAS WILL BE BUILDING FROM AROUND 2 FEET TO AS HIGH AS 4 FEET OFF THE DELAWARE COASTLINE DURING THE DAY TUESDAY AS A LOW PRESSURE TRACKS TO OUR SOUTHEAST. WIND GUSTS MAY INCREASE AS WELL TUESDAY AFTERNOON PERHAPS AS HIGH AS 20 KNOTS TUESDAY AFTERNOON OUT OF THE EAST. WINDS WILL MAINLY BE UNDER 10 KNOTS AND VARIABLE THROUGH THE EVENING. OUTLOOK... TUESDAY NIGHT THROUGH THURSDAY...ONSHORE FLOW CONTINUES BUT WILL WEAKEN OVER TIME. TSRA POSSIBLE IN SOUTHERN WATERS ON THURSDAY. FRIDAY THROUGH SATURDAY...SUB SMALL CRAFT ADVISORY WINDS EXPECTED. THE PERSISTENT ONSHORE FLOW MIGHT BRING SEAS TO SMALL CRAFT ADVISORY LEVELS FRIDAY AND POSSIBLY MORE LIKELY ON SATURDAY.
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&& .RIP CURRENTS...
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THE DEVELOPING EASTERLY SURFACE FLOW ALONG WITH 8 OR 9 SECOND SWELLS SHOULD RESULT IN A MODERATE RISK OF RIP CURRENTS ALONG THE NEW JERSEY SHORE ON TUESDAY. IT APPEARS AS THOUGH THE RISK WILL REMAIN LOW AT THE DELAWARE BEACHES.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GIGI/KLEIN NEAR TERM...IOVINO SHORT TERM...GAINES LONG TERM...GIGI AVIATION...GIGI/IOVINO MARINE...GAINES/GIGI/KLEIN RIP CURRENTS...IOVINO

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