Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 020753 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 353 AM EDT SAT MAY 2 2015 .SYNOPSIS... LOW PRESSURE OFF THE NORTH CAROLINA COAST WILL MOVE FARTHER OUT TO SEA TODAY. 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 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. A WEAK TROF IS FCST TO MOVE ACRS ERN PA AND WRN NJ THIS AFTN, AND IT CUD TRIGGER A SHWR, BUT POPS AND AREAL COVERAGE ARE BOTH LOW. && .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 /08Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDS ARE EXPECTED THRU THE TAF PD AS HIGH PRES BUILDS IN FROM THE W. THERE WILL BE SOME LINGERING SC AT TIMES THRU THE DAY BEFORE THE SKY BECOMES MAINLY CLR OVERNIGHT. WIND WILL SHIFT FROM NELY TO ELY AND EVENTUALLY S DURG THE DAY AND BECOME LIGHT OVERNIGHT. SPEEDS WILL REMAIN LESS THAN 10 KT. A SEA BREEZE FRONT IS EXPECTED TO WORK ITS WAY INLAND FROM THE CST DURG THE AFTN. OUTLOOK... SUNDAY 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. && .MARINE... THE SCA FLAGS WILL REMAIN IN EFFECT UNCHANGED. ITS PSBL SOME ADDITIONAL ADJUSTMENTS MAY BE NEEDED WRT TO THE EXPIRATION TIMES. 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 6 PM EDT THIS EVENING FOR ANZ452>455. SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ451. && $$ SYNOPSIS...KLEIN NEAR TERM...NIERENBERG SHORT TERM...NIERENBERG LONG TERM...KLEIN AVIATION...KLEIN/NIERENBERG MARINE...KLEIN/NIERENBERG

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