Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 021702 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 102 PM EDT SAT MAY 2 2015 .SYNOPSIS...
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LOW PRESSURE OFF THE NORTH CAROLINA COAST WILL MOVE FARTHER OUT TO SEA THIS AFTERNOON. AN EXPANSIVE AREA OF HIGH PRESSURE WILL REMAIN IN CONTROL OF THE EASTERN THIRD OF THE COUNTRY THIS WEEKEND. THE CENTER OF THE HIGH WILL SHIFT OFFSHORE SUNDAY NIGHT AND MONDAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST MONDAY NIGHT. THIS FRONT IS EXPECTED TO WEAKEN AND STALL OVER THE AREA TUESDAY INTO WEDNESDAY. HIGH PRESSURE BUILDS BACK INTO THE AREA LATE IN THE WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... CURRENT ESTF WE ADJUSTED MAX TEMPS UPWARD INLAND A COUPLE OF DEGREES BASED ON CURRENT OBS AND TRENDS. WE DIDNT CHANGE LOW POPS MUCH AS INLAND CU ARE SHOWING SOME VERTICAL DEVELOPMENT. SOUNDINGS LOOK CAPPED, SO THUNDER NOT EXPECTED EVENT THOUGH WE DO HAVE SOME CAPE AND SFC BASED LI(S) SHOULD BE DROPPING TO AROUND 0C. HIGH PRESSURE WILL SLOWLY BUILD INTO THE REGION FROM THE W AS LOW PRES OFF THE COAST MOVES AWAY FROM THE REGION. AS A RESULT, MAINLY DRY WX AND WARMING TEMPS ARE IN STORE TODAY. WITH LIGHT FLOW, TEMPS WILL BE COOLER ALG THE CST WHERE A SEABREEZE IS EXPECTED TO DEVELOP AND MOVE PRETTY FAR INLAND AS THE AFTERNOON PROGRESSES. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... THE SFC RIDGE WILL MOVE FURTHER INTO THE REGION TONIGHT AND EXPECT A GENLY CLEAR SKY AND NOT MUCH WIND. && .LONG TERM /SUNDAY THROUGH FRIDAY/... THE LARGE-SCALE PLAYERS NEXT WEEK INCLUDE PERSISTENT TROUGHING OVER THE WESTERN CONUS AND DOWNSTREAM RIDGING OVER MUCH OF THE EASTERN CONUS AND WESTERN ATLANTIC. THIS PATTERN WILL RESULT IN WARMER THAN NORMAL TEMPS AND FEW OPPORTUNITIES FOR PRECIPITATION FOR THE MID-ATLANTIC REGION FOR THE LONG-TERM PERIOD. MAX TEMPS GENERALLY RANGE FROM THE MID 70S TO LOWER 80S EACH DAY (EXCEPT COOLER ALONG THE COAST AND IN THE POCONOS). THE CENTER OF THE SURFACE HIGH PRESSURE AND H8 ANTICYCLONE WILL BE POSITIONED OVER THE SOUTHEAST STATES ON SUNDAY. THESE FEATURES WILL PROGRESS DOWNSTREAM TOWARD THE EAST COAST SUNDAY NIGHT AND THEN OVER THE WESTERN ATLANTIC ON MONDAY. SOUTHWESTERLY RETURN FLOW AROUND THE HIGH WILL DRAW EVEN WARMER AND SLIGHTLY MORE HUMID AIR UP THE EASTERN SEABOARD. A COLD FRONT IS EXPECTED TO DROP SOUTHWARD INTO THE REGION TUESDAY MORNING. THE COMBINATION OF UNIDIRECTIONAL W-SW FLOW ALOFT THAT BECOMES ORIENTED PARALLEL TO THE BOUNDARY AND DOWNSTREAM BLOCKING (FROM THE HIGH OVER THE WESTERN ATLANTIC AND CAROLINAS) WILL LIKELY CAUSE THE FRONT TO STALL OVER THE FORECAST AREA THRU WEDNESDAY. THE BOUNDARY WILL ALSO BECOME INCREASINGLY DIFFUSE DURING THIS TIME. THE BEST, IF NOT THE ONLY APPRECIABLE CHANCE FOR PRECIPITATION NEXT WEEK WILL BE TUESDAY-WEDNESDAY. WHILE FORCING FROM THIS DECAYING BOUNDARY ITSELF WILL BE WEAK, WE WILL HAVE TO WATCH FOR MID-LEVEL SHORTWAVE ENERGY THAT EJECTS OUT OF THE SOUTHWEST CONUS TROUGH TO RIDE ATOP THE DOWNSTREAM RIDGE AND EVENTUALLY MOVE INTO OUR AREA SOMETIME DURING THE TUESDAY AFTERNOON- WEDNESDAY MORNING PERIOD. THIS WOULD ENHANCE COVERAGE OF SHOWERS. HOWEVER, THE TIMING AND STRENGTH OF ANY SUCH IMPULSE IS STILL UNCERTAIN THIS FAR OUT, SO POPS WERE KEPT GENERALLY LOW. THE 00Z GUIDANCE PROGS THE GREATER INSTABILITY THAT MAY BE SUFFICIENT FOR CONVECTION TO BE CONFINED TO NEAR THE FRONT OWING TO MOISTURE POOLING ALONG THE BOUNDARY. KEPT CHANCES FOR THUNDERSTORMS LOW AREA WIDE DUE TO UNCERTAINTY IN THE LOCATION OF THE BOUNDARY. THE REMNANTS OF THE OLD FRONTAL BOUNDARY IS FORECAST TO BECOME WASHED OUT ACROSS THE AREA BY WEDNESDAY NIGHT. UPPER RIDGE BUILDING WILL OCCUR OVER THE MIDWEST AND MID ATLANTIC LATE IN THE WEEK. THIS ALLOWS THE WARMTH TO PERSIST ACROSS THE FORECAST AREA THRU THE END OF THE WEEK. MODELS ARE IN GOOD AGREEMENT WITH A CUTOFF LOW FORMING OFF THE SOUTHEAST COAST THURSDAY. WITH WEAK STEERING FLOW UNDERNEATH THE UPPER RIDGE, THE LOW IS NOT EXPECTED TO MAKE MUCH ADVANCEMENT TOWARD OUR AREA, RESULTING IN A DRY FORECAST FOR THURSDAY AND FRIDAY. && .AVIATION /18Z 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 ARE VFR. THIS AFTERNOON...CU BASED VFR CIG IS DEVELOPING NORTHWEST HALF OF OUR AREA AND THIS SHOULD CONTINUE. SOME ISOLATED SHOWERS ARE POSSIBLE NORTHWEST AIRPORTS, EVEN MORE ISOLATED THAN YESTERDAY AND WERE NOT INCLUDED. BIGGEST FEATURE WILL BE A SEA BREEZE FRONT THAT IS EXPECTED TO MAKE CONSIDERABLE WESTWARD MOVEMENT. PRECEDING IT WINDS SHOULD BE LIGHT FROM THE WEST TO NORTHWEST AT LESS THAN 10 KNOTS. THE SEA BREEZE FRONT IS ALREADY JUST INLAND IN MONMOUTH AND OCEAN COUNTIES AND BY 21Z SHOULD REACH KMIV-KVAY AND APPROACHING KSMQ. BY 23Z IT SHOULD BE THROUGH MOST OF 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 AFTERNOON AND MONDAY...VFR. LIGHT NW WINDS SUNDAY WILL BECOME SWLY AND INCREASE ON MONDAY. GUSTS TO 20 KT POSSIBLE MONDAY AFTERNOON. TUESDAY AND WEDNESDAY...PREDOMINATELY VFR. BRIEF/LOCAL RESTRICTIONS IN SCT SHOWERS AND ISO TSTMS AS A COLD FRONT DROPS SOUTHWARD AND THEN STALLS OVER THE AREA. BEST CHANCE FOR PRECIP WOULD BE TUESDAY AFTERNOON THRU WEDNESDAY MORNING.
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&& .MARINE... WE MADE A COUPLE OF CHANGES TO THE WINDS FOR THIS AFTERNOON AND EVENING BASED ON LATEST 12Z NAM AND SOME OF THE LATEST HRRR AND RAP AS THEY HAVE A DECENT WIND SHIFT/ SEA AND BAY BREEZE FRONT PREDICTED TO DEVELOP. WE WILL EXTEND THE SCA FOR A FEW MORE HOURS AS OBSERVED SEAS ARE ABOUT A FOOT ABOVE WAVE WATCH GUIDANCE. ONCE THIS CURRENT SCA COMES DOWN, NO ADDITIONAL MARINE HEADLINES ARE EXPECTED IN THE NR OR SHORT TERM PDS. OUTLOOK... SUNDAY THROUGH WEDNESDAY...WINDS AND WAVES WILL PREDOMINATELY STAY BELOW SCA CRITERIA. S-SW FLOW WILL INCREASE TO 15-20 KT MONDAY AFTERNOON THRU WEDNESDAY BUT THE WARM AIR ATOP THE COLDER WATERS WILL NOT PROVIDE MUCH OPPORTUNITY FOR STRONGER WINDS ALOFT TO MIX DOWN TO THE SURFACE. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ452>455. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ451. && $$ SYNOPSIS...KLEIN NEAR TERM...GIGI/NIERENBERG SHORT TERM...NIERENBERG LONG TERM...KLEIN AVIATION...GIGI/KLEIN MARINE...GIGI/KLEIN/NIERENBERG

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