Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 261948 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 348 PM EDT WED AUG 26 2015 .SYNOPSIS... HIGH PRESSURE ACROSS THE UPPER GREAT LAKES REGION WILL SETTLE ACROSS THE DELAWARE VALLEY BY FRIDAY AND THEN MOVE OFFSHORE THIS WEEKEND. A LOW PRESSURE SYSTEM AND FRONT WILL AFFECT THE WEATHER SUNDAY AND INTO EARLY MONDAY. MORE HIGH PRESSURE BUILDS ACROSS THE AREA NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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A GFS AND WRF-NMMB/NAM BLEND WOULD WORK THE BEST AS INITIALIZING AT 500MB EASTERN CONUS WHILE THE GFS REMAINS BETTER OUT WEST. THE SAME COMPROMISE WOULD WORK BEST AS A 925MB INITIALIZATION. BUT THE GFS ALONE LOOKED BETTER AT 850MB. THE INITIALIZATION DP/DT CONTINUES TO SHOW MORE RIDGING THAN FORECASTED IN THE WESTERN CONUS, BUT GENERALLY A FLATTER TROUGH IN THE EASTERN CONUS AND SOUTHEAST CANADA. GIVEN THE APPEARANCE OF THE CUMULUS AND CONTINUING CORROBORATION FROM RECENT HRRR RUNS, WE WILL KEEP THE ISOLATED SPRINKLES OVER THE FAR NORTHWEST FOR THE NEXT COUPLE OF HOURS. THE MAINLY CHANNELIZED VORT MAX IS EXPECTED TO REMAIN ACROSS THE NORTHWEST PART OF OUR CWA INTO THE OVERNIGHT, WITH THE LAST SHORT WAVE ROUNDING THE BASE OF THE TROF TOWARD MORNING. TENDENCY IS FOR WINDS TO BE LIGHTER THAN MODEL EXPECTATIONS PRECEDING THESE FEATURES ON ONE HAND. ON THE OTHER HAND, IT DOES RAISE THE UNCERTAINTY AS TO LINGERING CLOUDINESS, ESPECIALLY NORTHWEST. VISIBLE SATELLITE IS SHOWING PLENTY OF CLOUDINESS UPSTREAM AND SOME OF THE MORE HI RES MODELS DO KEEP LOW LEVEL MOISTURE GOING INTO THE EVENING. BUT, A TRAPPING INVERSION IS NOT BEING INDICATED. THUS THE FORECAST PLAN FOR THE NORTHWEST PART OF OUR CWA IS TO AVERAGE PARTLY CLOUDY FOR TONIGHT WITH A GENERALLY MORE HIGHER CONFIDENT AND CLEARER FORECAST SOUTHEAST. BOUNDARY LAYER WINDS ARE PREDICTED TO BE LIGHT ENOUGH FOR DECOUPLING, ESPECIALLY IN MORE SHELTERED AREAS. GIVEN THE AFTERNOON DEW POINTS, WE WENT WITH THE STAT GUIDANCE TREND OF LOWERING MINIMUM TEMPERATURES A BIT IN RURAL/OUTLYING AREAS. HIGHEST CONFIDENCE IS IN THE SOUTHERN PART OF OUR CWA. CLOUDS MAY MAKE OUR MINS NORTH TOO LOW.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
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WITH THE LAST OF THE SHORT WAVES MOVING OFFSHORE BY EARLY AFTERNOON THURSDAY, THE TROF FLATTENING AND A HIGH PRESSURE SYSTEM BUILDING INTO THE EASTERN GREAT LAKES, EVEN MORE OF A CHAMBER OF COMMERCE LATE AUGUST DAY IS PREDICTED FOR OUR CWA. THE MODELS DO PASS THE 250MB JET OVER DELMARVA. THEY ARE NOT SHOWING ANY JET LAYER MOISTURE AT THIS TIME. CUMULUS COVERAGE OVERALL SHOULD BE LESS THAN TODAY. THE THERMAL TROF PASSES THROUGH AND THE PREDICTED THERMALS SUGGEST ABOUT A 1F DROP OFF IN MAX TEMPS FROM TODAY. USING PREDICTED 925MB TEMPS, WE WILL FOLLOW A GFS AND NAM MOS COMPROMISE. A BRIEF NORTHWEST SURGE BEHIND THE COLD FRONT SHOULD BECOME LIGHTER AGAIN. ALONG AND NEAR THE COAST AND BAYS, SOME SEA BREEZE INDUCED WINDS COULD DEVELOP.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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5-WAVE MODEL GUIDANCE SHOWS A BUILDING SOUTHEAST RIDGE THROUGH A MAJORITY OF THE LONGTERM PERIOD WITH MODERATING TEMPERATURES AND HUMIDITY. FRIDAY - SATURDAY...EXPECTING A DRY FORECAST THESE DAYS WITH A WEAK FRONT NEARING FROM THE NORTHWEST. SOME GUIDANCE IS HINTING AT SHOWER ACTIVITY ACROSS THE NORTHERN SATURDAY AFTERNOON WITH A BIT OF A WEAKNESS IN THE PATTERN ALOFT BUT THINKING THAT CONVECTIVE TEMPERATURES SHOULD BE OUT OF REACH AND THE BETTER FORCING IS STILL FARTHER TO OUR NORTH AND WEST...WE STAY DRY. BOTH DAYS WE EXPECT TEMPERATURES IN THE MID-80S WITH DEWPOINTS CLOSE TO 60F. SUNDAY - MONDAY...THE AFOREMENTIONED COLD FRONT GETS CLOSER BUT WITH IT DOESN`T REALLY PACK A PUNCH BUT WE CONTINUE THE SLIGHT CHANCE WITH SOMEWHAT BETTER INSTABILITY. HIGH PRESSURE SLIDES OFF THE COAST AND ALLOWS FOR BETTER AIRMASS MODIFICATION SO WE WILL SEE AN INCREASE IN HUMIDITY AND INSTABILITY. HIGHS BOTH DAYS APPROACH, IF NOT EXCEED, 90F. TUESDAY - WEDNESDAY...NO APPRECIABLE RAIN EXPECTED EITHER DAY WITH SOUTHEAST RIDGE AXIS OVERHEAD. CONTINUED HEAT AND HUMIDITY INCREASE IS EXPECTED BUT IT DOES APPEAR THAT THE CORE OF THE WARMEST 925MB TEMPERATURES STAYS TO THE SOUTH AND WEST OF THE REGION. NONE-THE- LESS 90F IS NOT OUT OF THE QUESTION EACH AFTERNOON.
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&& .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. 18Z TAFS WERE VFR. REST OF THIS AFTERNOON...A HIGH BASED CUMULUS DECK, BECOMING A CIG AT TIMES AT THE NORTHWEST TERMINALS AND AIRPORTS. WEST WINDS WILL BE CLOSE TO 10 KNOTS. THE SEA BREEZE FRONT IS EXPECTED TO REMAIN NEAR THE IMMEDIATE NJ AND DE COAST AND NOT MAKE IT INLAND OR TO KACY. TONIGHT...THE CUMULUS CLOUDS SHOULD DISSIPATE, ESPECIALLY I95 CORRIDOR SOUTHEAST. WINDS WILL BE LIGHT FROM THE NORTHWEST AND MORE SHELTERED AIRPORTS/TERMINALS MAY GO CALM FOR A WHILE. NO VSBY RESTRICTIONS AT THE TERMINALS. LATE TONIGHT ANOTHER UPPER AIR DISTURBANCE MIGHT BRING SOME MID LEVEL CLOUDS ACROSS THE AREA AGAIN. HIGHEST CONFIDENCE NORTHWEST AIRPORTS AND TERMINALS. THURSDAY...A NEAR CARBON COPY OF TODAY. SOME HIGH BASED CUMULUS CLOUDS SHOULD DEVELOP AGAIN, PROBABLY LESS OVERALL COVERAGE THAN TODAY. NORTHWEST WINDS SHOULD AVERAGE 5 TO 10 KNOTS. A SEA BREEZE FRONT DURING THE AFTERNOON MIGHT MAKE MORE OF AN INLAND INTRUSION. OUTLOOK... THURSDAY NIGHT THRU SATURDAY NIGHT...MOSTLY VFR. PATCHY FOG PSBL DURING THE PREDAWN HOURS. SUNDAY - MONDAY...MOSTLY VFR. SHOWERS POSSIBLE WITH LOWER CONDITIONS.
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&& .MARINE...
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SUB SMALL CRAFT ADVISORY CONDITIONS WILL CONTINUE TONIGHT AND THURSDAY. SEA BREEZE INDUCED CIRCULATIONS LATE THIS AFTERNOON INTO THIS EVENING SHOULD BECOME A PREVAILING WEST TO NORTHWEST FLOW AGAIN TONIGHT. MESOSCALE MODELS HAVE THE STRONGEST (POSSIBLY EXCEEDING 15 KNOTS) SOUTHERLY FLOW EARLY OFF THE OCEAN AND ATLANTIC COUNTY COASTS WITH LESS VARIATION IN SPEEDS WITH THE NORTHWEST FLOW OVERNIGHT. AS THE OVERALL PRESSURE GRADIENT WEAKENS AGAIN DURING THE DAY ON THURSDAY, A MORE VARIABLE SEA BREEZE INDUCED WIND FLOW SHOULD DEVELOP AGAIN ON THE OCEAN WATERS. WE ARE NOT AS CERTAIN ABOUT AN UP (SOUTHEASTERLY WINDS) THE DELAWARE BAY FLOW OCCURRING. SUSTAINED WIND SPEEDS THURSDAY SHOULD REMAIN AT 15 KNOTS OR LESS. OUTLOOK... SUB-SCA CONDITIONS THRU THE PERIOD. SEAS WILL BUILD TO AROUND 4 FT ON THE OCEAN SAT NIGHT INTO SUNDAY. WIDELY SCT SHOWERS/TSTMS POSSIBLE SUN.
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&& .RIP CURRENTS...
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WE WILL CONTINUE THE MODERATE RISK FOR THE FORMATION OF DANGEROUS RIP CURRENT ALONG THE NJ BEACHES FOR THE REST OF THE DAY. A MORE FAVORABLE WIND FLOW FOR STRONGER RIP CURRENTS IS STARTING TO DEVELOP.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...O`HARA NEAR TERM...GIGI SHORT TERM...GIGI LONG TERM...HEAVENER AVIATION...GIGI/HEAVENER/O`HARA MARINE...GIGI/HEAVENER/O`HARA RIP CURRENTS...GIGI

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