Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251952 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 352 PM EDT TUE AUG 25 2015 .SYNOPSIS... A COLD FRONT WILL CONTINUE TO MOVE SLOWLY OFFSHORE TONIGHT. A HIGH PRESSURE SYSTEM WILL BUILD IN FROM THE UPPER MIDWEST ON WEDNESDAY AND THURSDAY. THE CENTER OF THE HIGH PRESSURE SYSTEM WILL MOVE OVERHEAD FRIDAY BEFORE RETREATING OFFSHORE THIS WEEKEND. THE HIGH PRESSURE SYSTEM WILL CONTINUE TO INFLUENCE OUR AREA THROUGH EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... INTO THIS EVENING AND TONIGHT, A COLD FRONT WILL CONTINUE TO EDGE A LITTLE FARTHER EAST AND OFFSHORE. MEANWHILE, A BROAD AREA OF HIGH PRESSURE STRETCHING ACROSS THE PLAINS AND MIDWEST WILL GRADUALLY BEGIN TO BUILD EAST TOWARD OUR REGION. OTHER THAN ISOLATED LATE-DAY SHOWERS FOR OUR COASTAL WATERS ASSOCIATED WITH THE COLD FRONT EXITING THE AREA, DRY WEATHER IS ANTICIPATED THROUGH TONIGHT. WESTERLY WINDS ARE EXPECTED TO BECOME MORE NORTHWESTERLY THROUGH THE OVERNIGHT, WITH MAINLY CLEAR SKIES FOR THE AREA, INCLUDING TOWARD THE COAST. DRIER AIR WILL CONTINUE TO FILTER IN ACROSS THE REGION, WITH DEWPOINTS FALLING INTO THE 50S FOR MOST LOCATIONS. OVERNIGHT MINIMUM TEMPERATURES WILL BE PLEASANT FOR LATE AUGUST, RUNNING NEAR TO SLIGHTLY BELOW AVERAGE. TEMPERATURES ARE EXPECTED TO BOTTOM OUT IN THE MIDDLE/UPPER 50S FOR OUR NORTHERN/WESTERN AREAS AND THE LOWER/MIDDLE 60S ELSEWHERE. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... SURFACE HIGH PRESSURE CENTERED OVER THE MIDWEST STATES WILL CONTINUE TO GRADUALLY BUILD INTO OUR REGION. A MID/UPPER TROUGH WILL BE PRESENT OVER MUCH OF THE EASTERN UNITED STATES, AND A SHORTWAVE TROUGH PASSING OVER OUR FORECAST AREA COULD TOUCH OFF AN ISOLATED SHOWER/SPRINKLE ACROSS THE HIGHER TERRAIN INTO THE POCONOS AND NORTHWEST NJ. OTHERWISE, DRY CONDITIONS ARE EXPECTED WITH AMPLE SUN AND SOME FAIR WEATHER CUMULUS. WEST-NORTHWEST WINDS ARE ANTICIPATED THROUGH THE DAY, WITH LOW HUMIDITY AS DEWPOINTS WILL REMAIN IN THE 50S. MAXIMUM TEMPERATURES WERE A MET/MAV GUIDANCE BLEND WITH CONTINUITY, AND WE ANTICIPATE HIGHS MAINLY IN THE LOWER/MIDDLE 80S FOR THE REGION, EXCEPT SOME 70S INTO THE HIGHER TERRAIN OF OUR NORTHWEST ZONES. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... THE 500MB PATTERN OF A BETTER GFS INITIALIZATION WEST AND EQUALLY GOOD TO SLIGHTLY BETTER NAMISH INITIALIZATION CENTRAL AND WEST CONTINUES. THE INITIALIZATION DP/DT CONTINUES TO TREND A STRONGER RIDGE WEST. GIVEN THE TREND, THIS WOULD MEAN A SLOWER TRANSITION IN THE EAST. A SNAP SHOT DP/DT ON THE SHEARING TROF APPROACHING THE WEEKEND SHOWS A WEAKENING TREND ON THE GFS. THE WEEKEND DIFFERENCE AS TO PCPN CHANCES VS NON WORTH MENTIONING PCPN CHANCES REMAIN. THE GFS STILL TAKES LONGER TO SHEAR THE TROF ROTATING AROUND THE WESTERN CONUS RIDGE. OTHER MODELS ARE FASTER AND THUS DRIER. THE HANDLING OR MIS HANDLING OF ERIKA PROBABLY PLAYS INTO THIS OUTCOME ALSO AS MOST OTHER MEDIUM RANGE MODELS HAVE MORE OF A SYSTEM THAN THE GFS. REGARDLESS OF THE PCPN OUTCOME, A DOWNRIGHT PLEASANT START TO THE LONG TERM WILL PROGRESSIVELY BECOME WARMER/HOTTER AND MORE HUMID ONCE AGAIN AS THE UPPER FLOW OVER THE EASTERN CONUS BECOMES WEAK AND AT LEAST A PIECE OF THE HEAT RIDGE BUILDS OVER US. THE LONG TERM STARTS WITH A PLEASANT WEDNESDAY NIGHT. THE PREDICTED BOUNDARY LAYER WINDS REMAIN RELATIVELY LIGHT. THE ONE CAVEAT IS THAT A WEAKENING SHORT WAVE (SOME CLOUDS) WILL BE MOVING THROUGH, ESPECIALLY NORTH. WE ARE GOING WITH A STAT GUIDANCE COMPROMISE. CONFIDENCE IS HIGHEST SOUTH WHERE THE EFFECT OF CLOUDINESS SHOULD BE THE LEAST. AS OPPOSED TO THE WESTERN RIDGE, THE MODELS HAVE TRENDED WITH A FASTER FLATTENING OF THE TROF ON THURSDAY. PREDICTED CONVECTIVE TEMP GETS REACHED FAR NORTH AND LATE IN THE DAY ELSEWHERE. THERMALLY THE GFS AND WRF-NMMB RUN ARE AT OPPOSITE ENDS OF THE SPECTRUM. BASED ON MUCH CLOSER MODEL PREDICTED 925MB TEMPS, WE WENT ABOUT TWO-THIRDS OF THE WAY TOWARD NAM MOS. THURSDAY NIGHT LOOKS LIKE "THE" RADIATIONAL COOLING NIGHT WITH THE HIGH PRESSURE SYSTEM MOVING ACROSS OUR CWA. WE ARE AT OR BELOW STAT GUIDANCE IN OUTLYING/RURAL AREAS. CONFIDENCE SWITCHES TO THE OPPOSITE END OF OUR CWA AS THERE ARE MODEL DIFFERENCES AS TO WHETHER JET INDUCED CIRRUS COULD BE AROUND FOR PART OF THE NIGHT IN OUR SOUTHERN CWA. VERY DEWY WINDSHIELDS ON FRIDAY MORNING. THE CLIMB TOWARD WARMER AND MORE HUMID WEATHER STARTS FRIDAY, BUT THE DAY IS EXPECTED TO ONLY SHOW A MINUSCULE RISE IN BOTH VS THURSDAY. THE MODELS ARE ALSO SHOWING CONVECTIVE TEMPS BEING REACHED ONLY LATE IN THE DAY, THUS ANOTHER CHAMBER OF COMMERCE DAY FOR OUTDOOR ACTIVITIES. LOOKING AT THE WEEKEND AS A WHOLE, THE GFS REMAINS MOST AGGRESSIVE WITH RETURN PCPN, WHILE MOST OTHER MEDIUM RANGE MODELS STILL BRING NO MEASURABLE PCPN AT ALL AS FAR EAST OR NORTHEAST. THE SATURDAY PCPN IS PREDICATED ON DEW POINTS THAT APPEAR TOO HIGH BASED ON AFTERNOON MIXING. GOING WITH WPC GUIDANCE LOWERS MIXED LAYER CAPES TO ZERO. ON SUNDAY THE PASS OF THE ENERGY AROUND THE WESTERN RIDGE SHOULD MAKE ITS CLOSEST ATTEMPT. THE ECMWF HAS TRENDED TOWARD A COMPROMISE POSN WITH THE GFS (THE LATTER TRENDING WEAKER). AS SUCH, WE WILL CARRY A LOW CHANCE WEST ASSUMING THE ECMWF TIMING OF WRN PA PCPN MAY BE A BIT TOO SLOW. AFTER A PLEASANT START SATURDAY MORNING, MAX TEMPS SHOULD BE ABOVE NORMAL AGAIN AND THE TREND SHOULD CONTINUE ON SUNDAY. THE MEDIUM RANGE SYNOPTIC SCALE MODELING TREND WITH ERIKA WAS WEAKER AND MORE TO THE LEFT (SOUTH). IT IS A CHICKEN VS EGG EFFECT AS THERE IS MORE RIDGING PREDICTED OVER OUR CWA. THUS WITH THE WEEKEND IMPULSE GETTING SHEARED AND NO BOUNDARIES NEARBY, NO ORGANIZED TRIGGERS AROUND. MONDAY AND TUESDAY SHOULD BE THE TYPE OF DAYS WHERE ISOLATED CONVECTION COULD HAPPEN, BUT NOT ENOUGH COVERAGE FOR POPS JUST YET. OUR MAX TEMPS ARE NEAR THE 90TH PERCENTILE OF OVERNIGHT ENSEMBLE MEMBERS AS THE 12Z RUN WAS HOTTER AGAIN. THESE TEMPS LOOKS VERY SIMILAR TO EARLY SEPTEMBER OF LAST YEAR. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. LATE-DAY AND TONIGHT...VFR CONDITIONS WILL CONTINUE, WITH SKIES BECOMING MAINLY CLEAR. WEST-NORTHWEST WINDS WILL AVERAGE IN THE 8 TO 10 KNOT RANGE THROUGH LATE-DAY BEFORE DECREASING TO 5 KNOTS OR LESS DURING TONIGHT. WINDS AT THE MORE RURAL TERMINALS MAY GO LIGHT AND VARIABLE OR EVEN CALM FOR A TIME DURING THE OVERNIGHT. WEDNESDAY...CONTINUED VFR CONDITIONS. SOME CUMULUS MAY DEVELOP IN THE AFTERNOON, WITH BASES AROUND 5000 FEET. WEST-NORTHWEST WINDS INCREASING INTO THE 8 TO 10 KNOT RANGE. OUTLOOK... WEDNESDAY NIGHT THROUGH THURSDAY...VFR. THURSDAY NIGHT THROUGH SUNDAY...PREDOMINATELY VFR THOUGH LOW CLOUDS AND/OR FOG ARE POSSIBLE EACH MORNING, ESPECIALLY IN THE MORE RURAL AND OUTLYING AIRPORTS. THE MORNING CHANCES SHOULD PROGRESSIVELY INCREASE EACH MORNING THROUGH SUNDAY. && .MARINE... OTHER THAN SOME ISOLATED LATE-DAY SHOWERS ASSOCIATED WITH A COLD FRONT MOVING FARTHER OFFSHORE, DRY WEATHER IS IN STORE FOR THE REGION AND OUR COASTAL WATERS. IN ADDITION, WINDS AND SEAS ARE EXPECTED TO REMAIN AT SUB-ADVISORY LEVELS THROUGH TONIGHT AND WEDNESDAY. WINDS WILL BECOME MORE WESTERLY INTO THIS EVENING AND THEN MORE NORTHWESTERLY INTO THE OVERNIGHT AND WEDNESDAY. SOME GUSTS BETWEEN 15 TO 20 KNOTS ARE POSSIBLE, ESPECIALLY FOR THE COASTAL WATERS. SEAS WILL AVERAGE IN THE 2 TO 4 FOOT RANGE FOR THE COASTAL WATERS, WITH 1 TO 2 FOOT SEAS INTO DELAWARE BAY. OUTLOOK... WEDNESDAY NIGHT THROUGH SUNDAY...NO MARINE HEADLINES ARE ANTICIPATED WITH A HIGH PRESSURE SYSTEM PREDOMINATING OVER OUR MARINE AREA. THERE SHOULD BE SOME RELATIVELY STRONGER RETURN FLOW WINDS AROUND SATURDAY, BUT BOTH WINDS AND SEAS ARE ANTICIPATED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA. && .RIP CURRENTS... A MODERATE RISK FOR THE FORMATION OF DANGEROUS RIP CURRENTS WILL CONTINUE FOR NJ THROUGH TODAY, AND A LOW RISK IS EXPECTED FOR DELAWARE. LONG PERIOD SWELLS ARE FORECAST TO CONTINUE THROUGH THE NEXT SEVERAL DAYS, AND THE CURRENT OUTLOOK IS FOR A MODERATE RISK OF DANGEROUS RIP CURRENTS TO CONTINUE AT THE BEACHES THROUGH THIS WEEK AND INTO THE WEEKEND. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GIGI/KLEIN NEAR TERM...KLINE SHORT TERM...KLINE LONG TERM...GIGI AVIATION...GIGI/KLEIN/KLINE MARINE...GIGI/KLEIN/KLINE RIP CURRENTS...KLINE

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