Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 220139 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 939 PM EDT MON APR 21 2014 .SYNOPSIS... A WEAK RIDGE OF HIGH PRESSURE JUST OFF THE MID- ATLANTIC COAST TONIGHT WILL GIVE WAY ON TUESDAY TO A COLD FRONT APPROACHING FROM THE WEST. THE FRONT WILL CROSS THE AREA AND MOVE OFFSHORE TUESDAY EVENING FOLLOWED BY HIGH PRESSURE BUILDING OVER THE REGION ON WEDNESDAY THROUGH THURSDAY. THE HIGH COMBINED WITH LOW PRESSURE EAST OF NEW ENGLAND WILL RESULT IN GUSTY NORTHWEST WINDS. ANOTHER FRONTAL SYSTEM WILL CROSS THE AREA FRIDAY OR FRIDAY NIGHT FOLLOWED BY MORE HIGH PRESSURE AND FAIR WEATHER FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 930 PM UPDATE...BIGGEST CHANGE WAS FOR THE POCONOS AND SOUTHEASTERN PA. NEARLY ALL OF THE SHORT RANGE MODELS CONTINUE TO WELL OVER FORECAST DEW POINT TEMPERATURES WEST OF THE I95 CORRIDOR. WHILE WE SHOULD HAVE INCREASING MOISTURE ADVECTION IN THE MID AND UPPER LEVELS THROUGH THE NIGHT, DO NOT SEE MUCH LOW LEVEL MOISTURE ADVECTION, ASIDE FROM THE TYPICAL NOCTURNAL INCREASE DUE TO DECOUPLING. THUS, IN ADDITION TO LOWERING DEW POINT TEMPERATURES IN THIS AREA, HAVE ALSO SLIGHTLY DECREASED LOWS GIVEN THE DRIER THAN EXPECTED AIR. OTHERWISE...NO OTHER SIGNIFICANT CHANGES TO THE FORECAST. PREVIOUS NEAR TERM DISCUSSION...CONTINUED FAIR AND QUIET WEATHER IS EXPECTED THIS EVENING AND TONIGHT AS WEAK SURFACE HIGH PRESSURE EASES FARTHER OFFSHORE AND AN AREA OF LOW PRESSURE TRACKS EAST ACROSS THE GREAT LAKES. ITS ASSOCIATED COLD FRONT WILL BE APPROACHING OUR REGION GOING INTO TUESDAY, BUT THE FRONT WILL REMAIN WELL TO OUR WEST THROUGH THE OVERNIGHT, ONLY NEARING THE APPALACHIANS AND FAR WESTERN PA BY AROUND DAYBREAK TUESDAY. THROUGH THE OVERNIGHT HOURS, FORECAST SOUNDINGS INDICATE INCREASING MOISTURE THROUGH THE COLUMN, WITH MORE HIGH/MID CLOUDS SPREADING INTO OUR AREA FROM WEST TO EAST, ESPECIALLY AFTER MIDNIGHT. OTHERWISE, A DRY FORECAST IS MAINTAINED THROUGH THE NIGHTTIME AND EARLY MORNING HOURS, WITH THE FRONT STILL WELL OFF TO OUR WEST. TEMPERATURES WILL BE NOTICEABLY MILDER THAN LAST NIGHT, WITH THE INCREASING CLOUDS AND LIGHT SOUTHERLY TO SOUTHWEST WINDS IN ADVANCE OF THE FRONT. FOR THE MOST PART, WE TOOK A BLEND OF MET/MAV GUIDANCE WITH SOME LOCAL ADJUSTMENTS AND ANTICIPATE MINIMUM TEMPERATURES MAINLY IN THE 40S ACROSS THE REGION. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... THROUGH THE DAYTIME TUESDAY, SURFACE LOW PRESSURE IS FORECAST TO PROGRESS EASTWARD FROM THE GREAT LAKES TO THE NEW ENGLAND STATES BY EVENING, WITH ITS ASSOCIATED COLD FRONT CROSSING OUR REGION DURING THE AFTERNOON TO EVENING HOURS. HIGHEST POPS ARE CENTERED AROUND THIS TIMEFRAME, WITH ONLY CHANCE TO SLIGHT CHANCE POPS FROM WEST TO EAST THROUGH THE MORNING HOURS. SLIGHT CHANCE THUNDER WAS KEPT ACROSS THE FORECAST AREA FOR THE AFTERNOON TO EVENING WITH THE FRONTAL PASSAGE, AS MODEL GUIDANCE CONTINUES TO INDICATE SOME INSTABILITY. THE PASSAGE OF THIS FRONT THROUGH OUR AREA CONTINUES TO LOOK RATHER PROGRESSIVE WITH FAIRLY LIMITED MOISTURE. THE GFS, NAM, AND ECMWF ALL GENERALLY HAVE AROUND A QUARTER OF AN INCH OR LESS QPF. IF ANY T-STORMS DO DEVELOP, SOMEWHAT HIGHER AMOUNTS MAY OCCUR. FOR TEMPERATURES, MILD SOUTHWESTERLY WINDS AHEAD OF THE FRONT AND FORECAST 925/850MB TEMPS LOOK TO SUPPORT DAYTIME HIGHS INTO THE LOWER 70S FOR MUCH OF THE REGION, WITH SOMEWHAT COOLER READINGS THROUGH THE HIGHER TERRAIN IN OUR NORTHWEST ZONES AND ALONG THE COAST. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... AT THE START OF THE LONG-TERM...00Z WED...A COLD FRONT IS FCST TO EXTEND N TO S ACROSS NJ AND DELMARVA. ASSOCD SHOWERS WILL BE OVER THE AREA AND A LITTLE BIT OF LINGERING CAPE IS EXPECTED SO HAVE LEFT IN THE MENTION OF ISOLD TSTMS FOR A COUPLE OF HOURS AFTER 00Z. PROB OF ANY THUNDER WILL BE RAPIDLY DECREASING AND ALL PRECIP SHOULD CLEAR THE AREA FROM W TO E BY MIDNIGHT WITH JUST A LINGERING CHANCE OF SHOWERS OVER FAR NW NJ AND THE POCONOS. STRONG LOW-LVL COLD ADVECTION WILL OCCUR OVERNIGHT BEHIND THE FRONT. ON WED...THE SFC LOW ASSOCD WITH THE COLD FRONT IS FCST TO DEEPEN EAST OF NEW ENGLAND AS HIGH PRES BUILDS IN FROM THE OH VLY. THE STG PRES GRADIENT WILL MAINTAIN GUSTY NW WINDS AND COLD ADVECTION WITH MAX TEMPS 10 TO 15 DEG F COOLER THAN ON TUESDAY. WITH GOOD PBL MIXING AND 850 HPA WINDS 40 TO 50 KT...SOME WIND GUSTS IN THE 30 TO 35 KT RANGE SEEM LIKELY FOR WEDNESDAY DAYTIME. THIS WINDY PATTERN WILL CONTINUE THROUGH WED NIGHT AND THURSDAY THO WITH THE USUAL NOCTURNAL DECREASE AND NOT QUITE AS STRONG ON THURSDAY AFTN AS THE HIGH PRES RIDGE MOVES CLOSER TO THE MID-ATLANTIC COAST. MAX TEMPS SHOULD RECOVER SOMEWHAT CLOSE TO NORMAL ON THURSDAY IN SPITE OF THE WIND. THE HIGH PRES RIDGE IS FCST TO MOVE OFF THE MID-ATLANTIC COAST ON FRIDAY AHEAD OF ANOTHER SHRTWV TROF AND ASSOCD FRONTAL SYS CROSSING THE AREA FRIDAY OR FRIDAY NIGHT. AT THIS RANGE THE TIMING IS MORE UNCERTAIN. FOR NOW WE HAVE THE HIGHER CHC POPS ON FRIDAY INTO FRIDAY NIGHT WITH LINGERING CHC POPS ON SAT OVER NRN NJ AND ADJACENT PA. CONFIDENCE IN THIS IS NOT TOO HIGH AT THE MOMENT. COLD ADVECTION BEHIND THE FRONT SHOULD RESULT IN COOLER TEMPS FOR THE WEEKEND BUT MAINLY FAIR SKIES LATER ON SAT AND INTO SUN. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. FOR THE 00Z TAFS...PRIMARILY VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. FOR TONIGHT, THERE IS A RISK OF BR DEVELOPING AT KMIV...AND POSSIBLY KACY WHILE WINDS ARE LIGHT AND VARIABLE, BEFORE THEY TURN TO A MORE SW DIRECTION NEAR SUNRISE. EXPECT INCREASING HIGH CLOUDS THROUGH THE OVERNIGHT INTO MORNING HOURS. SHOWERS, AND AN ASSOCIATED COLD FRONT WILL BEGIN TO APPROACH THE REGION AFTER 15Z, SPREADING FROM WEST TO EAST THROUGH THE AFTERNOON. GENERALLY VFR CONDITIONS ARE EXPECTED, THOUGH SOME LOCALIZED MVFR CONDITIONS ARE POSSIBLE IN HEAVIER SHRA. WHILE ISOLATED THUNDER IS NOT OUT OF THE QUESTION AS THERE WILL BE SOME INSTABILITY, CONFIDENCE WAS NOT HIGH ENOUGH AT THIS TIME TO INCLUDE THUNDER IN THE TAFS. OUTLOOK... TUESDAY NIGHT...SOME SCATTERED SHOWERS WITH LOCALLY MVFR CONDS IN THE EVENING...THEN IMPROVING TO GENERALLY VFR OVERNIGHT. WEDNESDAY THROUGH THURSDAY...VFR CONDITIONS PREVAILING BUT VERY GUSTY NW WINDS...ESPECIALLY ON WEDNESDAY. FRIDAY THROUGH SATURDAY...MAINLY VFR BUT LOCALLY MVFR IN SCATTERED SHOWERS. && .MARINE... 930 PM UPDATE...WAVE HEIGHTS AT BUOY 44009 REMAIN NEAR OR JUST ABOVE 5 FT, SO THE SMALL CRAFT ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT. WAVE HEIGHTS ARE EXPECTED TO SLOWLY DECREASE OVER THE NEXT FEW HOURS, AND SHOULD BE BELOW 5 FT AFTER MIDNIGHT. PREVIOUS MARINE DISCUSSION...AT LATE-DAY, SOME ENHANCED SEAS STILL EXIST ON OUR COASTAL WATERS, WITH MAINLY THE OUTER WATERS STILL REACHING IN THE 5 TO 6 FOOT RANGE, INCLUDING BUOY 44009. WE WILL CONTINUE WITH THE CURRENT SMALL CRAFT ADVISORY FOR OUR COASTAL WATERS, WHICH EXCLUDES OUR NORTHERNMOST ZONE FROM MANASQUAN INLET NORTHWARD TO SANDY HOOK. WHILE THE SEAS ARE DIMINISHING, GUIDANCE STILL SHOWS A FEW MORE HOURS INTO THIS EVENING OF ELEVATED SEAS. MEANWHILE, WINDS ARE BELOW SCA CRITERIA AT 15 KNOTS OR LESS, AND THEY WILL REMAIN SO THROUGH TONIGHT. ONCE SEAS SUBSIDE LATER TONIGHT, THE OVERNIGHT PERIOD AND THROUGH MOST OF THE DAYTIME TUESDAY WILL BE AT SUB-SCA LEVELS FOR OUR COASTAL WATERS AND DELAWARE BAY AS A COLD FRONT SLOWLY APPROACHES FROM THE WEST. SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS WILL BECOME MORE LIKELY ACROSS THE WATERS DURING THE LATE AFTERNOON TO EVENING HOURS ON TUESDAY. OUTLOOK... TUESDAY NIGHT THROUGH THURSDAY...NORTHWEST WINDS GUSTING 25 TO 30 KT. SOME GALE FORCE GUSTS ARE POSSIBLE ON WEDNESDAY. FRIDAY AND SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED AT THIS TIME. && .FIRE WEATHER... SOME FIRE WEATHER DANGER MAY BE PRESENT ON WEDNESDAY AND THURSDAY. GUSTY NORTHWEST WINDS WILL BE PRESENT BOTH DAYS BUT SOMEWHAT STRONGER ON WEDNESDAY. HOWEVER...AT THIS TIME IT LOOKS LIKE RH VALUES MAY STAY ABOVE 30 PERCENT ON WEDNESDAY. RH WILL BE LOWER ON THURSDAY WITH ADDITIONAL DRYING AFTER TUESDAYS PRECIP...AND STILL GUSTY NW WINDS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ451>455. && $$ SYNOPSIS...AMC NEAR TERM...JOHNSON/KLINE SHORT TERM...KLINE LONG TERM...AMC AVIATION...AMC/JOHNSON/KLINE MARINE...AMC/JOHNSON/KLINE FIRE WEATHER...AMC

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