Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 021948 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 348 PM EDT SAT MAY 2 2015 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN TO OUR SOUTH THROUGH MONDAY, KEEPING FAIR WEATHER ACROSS THE AREA. A COLD FRONT IS FORECAST TO MOVE ACROSS THE AREA TUESDAY, THEN STALL SOUTH OF THE AREA THROUGH THE END OF THE WEEK.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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A COMBINATION OF THE GFS AND WRF-NMM LOOKED BEST OFF THE 500MB INITIALIZATION WITH A SLIGHT NOD TO THE WRF-NMMB AT BOTH 850MB AND 925MB WHERE THE GFS SHOWED SOME 1C COLD BIASES. MODERATING TREND THROUGH THE SHORT TERM WILL CONTINUE WITH LITTLE IF ANY PCPN AND NO PCPN EXPECTED AFTER EARLY THIS EVENING. THE HRRR HAD A GOOD HANDLE ON LOCATIONS OF BULKIER CU AND ADJUSTMENTS TO ISOLATED SHOWERS (MORE LIKELY JUST SPRINKLES OR A FEW BIG DROPS HITTING THE WINDSHIELD) WERE BASED ON ITS LATEST OUTPUT. FORECAST SOUNDINGS STILL ARE CAPPED AND WITH THE SHORT WAVE MOVING OFFSHORE SHOULD ONLY BECOME MORE SO AS THE AFTN AND EARLY EVE PROGRESS, SO NO THUNDER. BASED ON UPWIND SATL INFO, DOESNT LOOK LIKE CLOUDS ARE GOING TO GET TRAPPED UNDER THE INVERSION, SO MOST SHOULD BE GONE BY EVENING`S END. WINDS WILL BE LIGHT, IF NOT CALM, IN MOST AREAS. WE RADIATED MIN TEMPS DOWN TOWARD THE LOWER STAT GUIDANCE DATASETS.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
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INCREASED RIDGING AND FARTHER OFFSHORE MOVEMENT OF THE 500MB TROF AND SFC LOW WILL TRANSLATE INTO A WARMER DAY ON SUNDAY WITH LESS CUMULUS CLOUDS AROUND AND NO CHANCE FOR PCPN. 18C AIR AT BOTH 925MB AND 850MB OVER THE UPPER PLAINS WILL START MAKING A TURN TOWARD OUR CWA, BUT NOT ARRIVE IN TIME FOR SUNDAY. NEVERTHELESS, THERE WILL BE A SEVERAL DEG C UPTICK IN TEMPS AT BOTH THOSE LEVELS SUNDAY. LIKE TODAY, THE WARMER PART OF OUR AIR MASS WILL BE OVER THE NWRN PART OF OUR CWA VS SOUTHEAST. THUS MAX TEMPS (AWAY FROM THE IMMEDIATE SHORE AND HIGHER TERRAIN) ARE PREDICTED TO BE QUITE UNIFORM. THIS IS IN LINE WITH FCST CONTINUITY AND THE HIGHER MOS DATASETS. A SEA BREEZE FRONT SHOULD FORM AGAIN, LIKELY NOT AS VIGOROUS AS TODAY`S. NONETHELESS SOME COOLING WILL OCCUR AT OR CLOSER TO THE COAST AS THE AFTERNOON PROGRESSES. WATER TEMPS ARE STILL QUITE CHILLY.
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&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
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THE HIGH PRESSURE TO OUR SOUTH BUILDS SLIGHTLY FURTHER OFFSHORE SUNDAY NIGHT, BUT MOSTLY REMAINS IN PLACE THROUGH MONDAY. THE HIGH WILL BEGIN GETTING SQUEEZED FURTHER OFFSHORE AND AWAY FROM THE AREA MONDAY NIGHT. HOWEVER, OUR AREA ON THE NORTHERN FRINGE OF THE HIGH THROUGH MONDAY NIGHT, WHICH WILL KEEP RATHER TRANQUIL WEATHER ACROSS THE AREA THROUGH MONDAY NIGHT. A COLD FRONT IS FORECAST TO MOVE ACROSS THE AREA TUESDAY INTO TUESDAY NIGHT, WHILE PW VALUES INCREASE TO AROUND 1.0-1.5 INCHES. WITH AN INCREASE IN MOISTURE AND WARM TEMPERATURES, THERE IS SOME INSTABILITY FORECAST, WITH MLCAPE VALUES AROUND 500 J/KG, SLIGHTLY NEGATIVE LI VALUES, AND TOTAL TOTAL VALUES NEAR 50. SO AS THE FRONT MOVES THROUGH THE AREA, SCATTERED SHOWERS ARE EXPECTED, ALONG WITH ISOLATED THUNDERSTORMS. THE FRONT SHOULD MOVE ACROSS THE AREA INTO TUESDAY NIGHT, AND SHOWER/THUNDERSTORM ACTIVITY SHOULD MOVE THROUGH WITH THE FRONT AND/OR DIMINISH THROUGH THE NIGHT. AS THE FRONT SLOWLY PASSES THROUGH THE AREA TUESDAY NIGHT INTO WEDNESDAY, IT IS FORECAST TO STALL OUT TO OUR SOUTH THROUGH THE REMAINDER OF THE WEEK, AND MAY END UP WASHING OUT TO OUR SOUTH. WITH THE FRONT TO OUR SOUTH, HIGH PRESSURE FROM THE NORTH WILL TRY TO NOSE ITS WAY INTO THE AREA THROUGH THE END OF THE WEEK. THIS SHOULD KEEP THE WEATHER DRY THROUGH FRIDAY, AND WITH RIDGING BUILDING ALOFT, TEMPERATURES ARE FORECAST TO REMAIN ABOVE NORMAL THROUGH THE END OF THE WEEK. WEDNESDAY MAY BE THE COOLEST DAY WITH A NORTH/NORTHEAST FLOW ACROSS THE AREA WHICH MAY BRING IN COOLER AIR AND KEEP CLOUD COVER IN AS WELL. THE DRY WEATHER SHOULD REMAIN THROUGH FRIDAY NIGHT, BUT ISOLATED SHOWERS MAY RETURN FOR SATURDAY AS RETURN FLOW DEVELOPS ACROSS THE AREA, INCREASING MOISTURE AND DAYTIME INSTABILITY ACROSS THE AREA WHICH COULD LEAD TO A SLIGHT CHANCE OF SHOWERS, ESPECIALLY ACROSS THE WESTERN HALF OF THE AREA.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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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...CU BASED VFR CIG FROM THE DELAWARE RIVER VALLEY TERMINALS NORTHWESTWARD. WE EXPECT KACY AND KMIV TO PREVAIL WITHOUT A CIG. SOME ISOLATED SHOWERS ARE POSSIBLE NORTHERN AIRPORTS, EVEN MORE ISOLATED THAN YESTERDAY AND WERE NOT INCLUDED. SEA BREEZE FRONT IS MAKING CONSIDERABLE WESTWARD MOVEMENT. AT 20Z IT WAS FROM ABOUT KMIV TO CHATSWORTH IN BURLINGTON COUNTY THRU MOST OF OCEAN COUNTY AND ALONG THE MIDDLESEX AND MONMOUTH COUNTY LINE. PRECEDING IT WINDS ARE LIGHT FROM A WESTERLY COMPONENT AT LESS THAN 10 KNOTS. BY 21Z SEA/BAY BREEZE FRONT SHOULD SHOULD BE THROUGH ALL OF DELAWARE BAY TO KVAY AND KSMQ. BY 23Z MORE CONFIDENT IT SHOULD BE THROUGH DELAWARE AND THE DELAWARE RIVER AIRPORTS INCLUDING KPHL AND BE APPROACHING KLOM AND KDYL. WINDS BEHIND THE SEA BREEZE FRONT SHOULD BE SOUTH TO SOUTHEAST AT AROUND 10 KNOTS. THIS EVENING...THE SEA BREEZE FRONT ADVANCEMENT SHOULD SLOW. IT MIGHT MAKE IT TO KABE. OTHERWISE WINDS WILL BE LIGHT AND VARIABLE WITH SOME VFR ISOLATED/SCATTERED MID LEVEL DEBRIS CLOUDS. OVERNIGHT...CLEAR SKIES AND LIGHT AND VARIABLE WINDS. WE DO NOT HAVE FOG PREDICTED AT THE TERMINALS. CONFIDENCE ABOUT NO FOG AT MORE RURAL AIRPORTS IS MODERATE. AIR MASS HAS BEEN CLEAN AND DEW POINTS ARE NOT RISING THIS AFTERNOON. SUNDAY MORNING INTO EARLY AFTERNOON...VFR NO CIG EXPECTED, LESS CUMULUS CLOUDS THAN TODAY. WINDS BECOMING WEST AT 5 TO 10 KNOTS. ANOTHER SEA BREEZE FRONT IS EXPECTED TO DEVELOP AND WE START THAT AT KACY AT 17Z. OUTLOOK... SUNDAY NIGHT-MONDAY NIGHT...VFR. SOUTHWEST WIND GUSTS AROUND 20 KNOTS MONDAY. TUESDAY-TUESDAY NIGHT...GENERALLY VFR WITH SHOWERS POSSIBLE. SOUTHWEST WIND GUSTS AROUND 20 KNOTS TUESDAY. WEDNESDAY...MOSTLY VFR, POSSIBLE NEAR MVFR CIGS. WEDNESDAY NIGHT-THURSDAY...IMPROVING CONDITIONS TO VFR OVERNIGHT AND CONTINUING THROUGH THURSDAY.
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&& .MARINE...
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SEAS CONTINUE TO BE SLOWER TO SUBSIDE THAN ANTICIPATED AS THE OFFSHORE PROGRESSION OF THE LOW IS NOT FAST ENOUGH TO NEGATE THE WESTWARD PROPAGATION OF HIGHER SEAS. WAVE WATCH GUIDANCE CONTINUES TO RUN APPROXIMATELY HALF A FOOT TOO LOW. BUOY65 SEAS HAVE BEEN HOLDING AT 4 FEET, SO WE WILL HOLD OFF ON REISSUING A SCA FOR THE MONMOUTH COASTAL WATERS. THE OTHER COASTAL WATERS, WE WILL EXTEND THE SCA FOR SEVERAL MORE HOURS INTO THE NIGHT. ON DELAWARE BAY, IN THE NEAR TERM A STRONG BAY BREEZE WILL WORK ITS WAY UP THE BAY, BUT GUSTS SHOULD BE JUST BELOW SCA CRITERIA. WINDS WILL DECREASE THIS EVENING. WE REMAIN CONFIDENT THAT SUB SMALL CRAFT ADVISORY CONDITIONS WILL OCCUR ON SUNDAY AS THE LOW MOVES FARTHER OFFSHORE AND A HIGH PRESSURE RIDGES OVER THE COASTAL WATERS. A SEA BREEZE FLOW SHOULD DEVELOP AGAIN AND CHANNEL UP DELAWARE BAY. OUTLOOK... SUNDAY NIGHT-THURSDAY...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED. HOWEVER, WINDS MAY GUST AROUND 20 KNOTS AND SEAS APPROACH 4 FEET THROUGH THE PERIOD. FRONTAL BOUNDARY IS EXPECTED TO MOVE SOUTH OF THE WATERS ON TUESDAY AND STALL TO OUR SOUTH THROUGH THE END OF THE WEEK.
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&& .FIRE WEATHER...
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RELATIVE HUMIDITY VALUES AROUND 25-30 PERCENT, ALONG WITH WIND GUSTS OF 20-25 MPH WILL LEAD TO ENHANCED FIRE WEATHER CONCERNS ON MONDAY FOR PORTIONS OF THE FORECAST AREA.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EDT SUNDAY FOR ANZ452>455. SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ451.
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&& $$ SYNOPSIS...ROBERTSON NEAR TERM...GIGI SHORT TERM...GIGI LONG TERM...ROBERTSON AVIATION...GIGI/ROBERTSON MARINE...GIGI/ROBERTSON FIRE WEATHER...ROBERTSON

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