Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 172009 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 409 PM EDT FRI APR 17 2015 .SYNOPSIS...
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A WEAK SURFACE TROUGH WILL CROSS THE REGION TONIGHT WITH A COLD FRONT CROSSING THE REGION SATURDAY AFTERNOON. WEAK HIGH PRESSURE WILL NOSE DOWN FROM THE NORTH ON SUNDAY. A WARM FRONT WILL PUSH NORTHWARD INTO OUR REGION ON MONDAY, FOLLOWED BY A COLD FRONTAL PASSAGE MONDAY NIGHT. ANOTHER FRONTAL PASSAGE IS EXPECTED LATE WEDNESDAY INTO THURSDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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A SURFACE TROUGH WAS ANALYZED OVER VA, EXTENDING NEWD ALONG THE FALL LINE INTO E PA. THE CONVECTIVE ALLOWING HIRES MODELS CONTINUE TO SIMULATE A LINE OF SHOWERS AND EVEN ISO THUNDERSTORMS DEVELOPING ALONG THIS BOUNDARY THIS AFTERNOON. WHILE CONVECTION HAS INITIATED IN VA, WHERE MORE PRONOUNCED LOW-LEVEL CONVERGENCE HAS PROVIDED STRONGER LIFT AND SUNSHINE HAS ALLOWED FOR GREATER DESTABILIZATION, IT HAS YET TO DEVELOP ACROSS OUR FORECAST AREA. IT TOOK THE ATMOSPHERE LONGER TO REBOUND IN OUR AREA DUE TO THE MORE STUBBORN CLOUD COVER EARLIER IN THE DAY BUT BREAKS IN THE CLOUDS CONTINUE TO EXPAND SO WE STILL EXPECT SHOWERS TO DEVELOP MAINLY LATE THIS AFTERNOON. A HIGHER RIBBON OF HEATING AND INSTABILITY WILL PROVIDE SLIGHTLY BETTER CHANCES FOR LATE DAY CONVECTION (OVER SE PA, S NJ AND THE DELMARVA. CONFINED ISO THUNDERSTORMS TO THESE SOUTHERN AREAS. THIS ACTIVITY SHOULD WEAKEN AFTER SUNSET AS IT MOVES THRU THE I-95 CORRIDOR AND COASTAL AREAS. SKIES EXPECTED TO CLEAR FROM WEST TO EAST LATE THIS EVENING AND OVERNIGHT. WINDS SHIFT OUT OF THE NW FOLLOWING THE PASSAGE OF THE AFOREMENTIONED SURFACE TROUGH BUT THEY WILL BE LIGHT. PATCHY FOG MAY DEVELOP IN AREAS THAT RECEIVE RAINFALL THIS EVENING.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
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THE FORECAST AREA WILL BE SITUATED JUST TO THE S OF THE FAST W TO NW FLOW ALOFT THAT RESIDES TOWARD THE BASE OF AN UPPER TROUGH. THIS UPPER TROUGH IS EXPECTED TO DIG E-SEWD THRU NEW ENGLAND IN THE AFTERNOON. AT THE SURFACE...HIGH PRESSURE OVER CENTRAL CANADA WILL RIDGE S AND EWD TOWARD THE OH VALLEY AND MID-ATLANTIC STATES IN THE MORNING. SURFACE LOW PRESSURE ASSOCIATED WITH THE AFOREMENTIONED UPPER WAVE WILL TRACK ACROSS NEW ENGLAND IN THE AFTERNOON. NW FLOW BEHIND THE LOW WILL BE ALLOW ITS COLD FRONT TO SURGE SEWD ACROSS NE PA AND NW NJ DURING THE MID AFTERNOON AND LATE AFTERNOON TO EARLY EVENING FARTHER S AND E. NOT MUCH CHANGE IN THINKING FROM THE PREVIOUS SHIFT WITH REGARDS TO LEANING ON THE WARM SIDE OF TEMP GUIDANCE IN THIS SETUP. WE WILL BE POSITIONED IN THE PRE-FRONTAL WARM SECTOR WHERE DEEP MIXING PROFILES WILL DEVELOP AS A RESULT OF STRONG DAYTIME HEATING AND DOWNSLOPING FLOW. HIGHS IN THE MID TO UPPER 70S WILL BE COMMON EXCEPT COOLER IN THE POCONOS AND ALONG THE COAST. WOULD NOT BE SURPRISED TO SEE A FEW WARMER SPOTS TO REACH 80F. WLY WINDS AROUND 10 TO 15 MPH WILL SHIFT OUT OF THE NW AND BECOME GUSTY LATE IN THE DAY AFTER THE COLD FRONT MOVES THRU.
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&& .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
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SATURDAY NIGHT THROUGH SUNDAY...FOR THE MOST PART THIS PERIOD LOOKS TO BE FAIRLY QUIET. HIGH PRESSURE WILL NOSE DOWN FROM THE NORTH BRINGING IN SOME COOLER AIR FOR SATURDAY NIGHT THROUGH SUNDAY. DRY CONDITIONS WILL PREVAIL THROUGH MOST OF SUNDAY WITH INCREASING CLOUDINESS AND INCREASING MOISTURE IN ADVANCE OF AN APPROACHING WARM FRONT. RAIN SHOWERS WILL START PUSH INTO THE AREA LATE SUNDAY. MONDAY THROUGH TUESDAY...MOISTURE WILL CONTINUE TO INCREASE AS THE WARM FRONT PROGRESSES NORTHWARD INTO AND THROUGH OUR AREA. PRECIPITABLE WATER VALUES WILL RISE UP NEAR 1.5 INCHES ACROSS THE REGION WHICH WILL CAUSE RAIN TO BECOME HEAVY AT TIMES. WE HAVE ADDED SOME THUNDER INTO THE FORECAST FOR MONDAY AFTERNOON/EVENING AS SOME INSTABILITY OCCURS WHILE WE ARE IN THE WARM SECTOR, BEHIND THE WARM FRONT AND BEFORE THE COLD FRONT PUSHES THROUGH THE REGION. CHANCES FOR THUNDER LOOK BETTER AS YOU HEAD TO THE SOUTH AND EAST OF PHL WITH WEAKER INSTABILITY TO THE NORTH AND WEST. WE HAVE INCLUDED A CHANCE OF THUNDER FOR THOSE AREAS TO THE SOUTH AND EAST OF PHL AND CONTINUE TO LEAVE OUT OF OTHER AREAS AT THIS TIME. GUSTY SOUTHEASTERLY WINDS WILL ALSO OCCUR, ESPECIALLY ALONG THE COASTAL AREAS, A STRONG LOW LEVEL JET CROSSES THE REGION ON MONDAY. RAIN, WITH RUMBLES OF THUNDER TO THE SOUTH, WILL GRADUALLY TAPER OFF TO THE NORTH AND EAST THROUGH THE EVENING AND INTO THE OVERNIGHT HOURS. THE COLD FRONT ARRIVES OVERNIGHT AND SHOULD BE LEAVING THE AREA TUESDAY MORNING. SHOWERS WILL END AS THE FRONT PASSES TO THE EAST BUT WITH A PERSISTENT UPPER LEVEL TROUGH NEARBY, SHOWERS MAY CONTINUE ACROSS THE NORTHERN AREAS THROUGH THE AFTERNOON. WEDNESDAY THROUGH FRIDAY....A PERSISTENT UPPER LEVEL TROUGH WILL SPIN OVER THE GREAT LAKES AREA WITH A GRADUAL PUSH TO EAST THROUGH THE WEEK. SEVERAL SHORTWAVES EMBEDDED IN THE UPPER LEVEL FLOW WILL ROTATE THROUGH OUR AREA AND PUSH A COLD FRONT THROUGH OUR AREA LATE WEDNESDAY INTO THURSDAY. SHOWERS WILL REMAIN POSSIBLE, ESPECIALLY ACROSS THE NORTHERN AREAS. AS THE FRONT DROPS TO THE SOUTH OF THE AREA, IT MIGHT STALL AND WEAK WAVE MAY MOVE ALONG IT AND THROUGH THE SOUTHERN AREAS ON THURSDAY. SOME LIGHT SHOWERS MAY OCCUR AS A RESULT OF THIS FEATURE. THE MODEL SOLUTIONS DIVERGE BEYOND WEDNESDAY AND PLENTY OF UNCERTAINTY AS TO WHICH FEATURES WILL IMPACT OUR AREA THROUGH THE END OF THE WEEK.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. CIGS CONTINUE TO IMPROVE ACROSS THE AREA SO FAR THIS AFTN. ONLY TTN AND ACY ARE STILL AT MVFR BUT THEY SHOULD GRADUALLY IMPROVE TO VFR BY 21Z. THERE IS A POTENTIAL FOR LOCALIZED/BRIEF FLIGHT RESTRICTIONS (BOTH CIGS AND VSBYS) IN SCT SHRA. THESE SHRA HAVE NOT YET DEVELOPED BUT MOST OF THE HIRES GUIDANCE CONTINUES TO SHOW IT DEVELOP OVER THE HIGHER TERRAIN IN NE PA MID AFTN, I-95 TERMINALS BETWEEN 22Z AND 00Z AND MIV/ACY BETWEEN 23Z AND 02Z. LIMITED THE SHRA TO A TEMPO GROUP DUE TO LOW COVERAGE. ALSO DID NOT INCLUDE TSRA IN THE TAFS DUE TO THE VERY SPARSE COVERAGE EXPECTED. IF AN ISO TSRA DOES DEVELOP, IT WOULD MORE LIKELY BE IN FAR SE PA AND THE DELMARVA. W-SW 5-10 KT LATE THIS AFTN. PREDOMINATELY VFR EXPECTED TONIGHT AS SKIES CLEAR LATE THIS EVE AND OVNGT. HOWEVER, PATCHY FOG COULD DEVELOP IN THE TYPICAL FOG-PRONE TERMINALS EARLY IN THE MORNING. A TEMPO GROUP FOR MVFR VSBY RESTRICTIONS WAS INCLUDED AT THOSE TAF SITES. WINDS WILL BECOME LIGHT AND VARIABLE TONIGHT. VFR ON SATURDAY. LIGHT WINDS IN THE MORNING WILL INCREASE IN THE AFTN TO AROUND 10 KT. WIND GUSTS TO 20 KT POSSIBLE LATE IN THE DAY. OUTLOOK... SATURDAY NIGHT THROUGH SUNDAY...MAINLY VFR CONDITIONS ARE EXPECTED. INCREASING CLOUDINESS THROUGH SUNDAY WITH SOME SHOWERS DEVELOPING LATE. NORTHEAST TO EAST WINDS AROUND 10 KNOTS. MONDAY...MVFR/IFR CONDITIONS WITH PERIODS OF RAIN. LOW LEVEL WIND SHEAR IS POSSIBLE FOR A TIME ON MONDAY. SOUTHEAST WINDS 10 TO 15 KNOTS EXPECTED. TUESDAY...MVFR/IFR CONDITIONS EARLY WITH IMPROVING CONDITIONS AS RAIN EXITS TO THE NORTH AND EAST OF THE TERMINALS. HOWEVER, SOME SHOWERS REMAIN POSSIBLE THROUGH THE DAY. LIGHT WESTERLY WINDS. WEDNESDAY...MAINLY VFR CONDITIONS EXPECTED. SHOWERS ARE POSSIBLE, MAINLY FROM KPHL AND TO THE NORTH AND WEST. LIGHT WESTERLY WINDS.
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&& .MARINE...
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LIGHT SW WINDS LATE THIS AFTN AND EVE WILL BECOME VARIABLE LATE TONIGHT. THESE WINDS WILL ADVECT WARM, MOIST AIR UP THE COAST DURING THIS TIME, UNTIL THE SURFACE TROUGH ARRIVES. AS A RESULT, SOME FOG MAY DEVELOP OVER THE WATERS TONIGHT. KEPT VSBYS AT 1-2 NM BUT IF FOG BECOMES MORE DENSE THAN FORECAST, THEN A DENSE FOG ADVISORY MAY BE NEEDED. OUTLOOK... SATURDAY NIGHT AND SUNDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED. SOME GUSTS NEAR 25 KNOTS LATE SUNDAY. MONDAY THROUGH TUESDAY...WINDS WILL INCREASE AS A RESULT OF A STRENGTHENING LOW LEVEL JET MOVING ACROSS THE REGION. WITH MORE STABLE AIR AT THE SURFACE, IT MAY BE DIFFICULT TO MIX DOWN SOME OF THE STRONGER WINDS JUST ABOVE THE SURFACE. HOWEVER, GUSTY SOUTHEASTERLY WINDS WILL OCCUR AT THE SURFACE AND WE MAY SEE SOME GUSTS AROUND 30 KNOTS ON MONDAY. AS THE JET MOVES THROUGH, ALONG WITH A FRONTAL SYSTEM, WINDS WILL TURN MORE SOUTHERLY AND THEN BECOME MORE WESTERLY THROUGH TUESDAY, WEAKENING THROUGH THAT TIME. SEAS WILL BUILD AND EXCEED 5 FEET ON THE OCEAN AND MAY BE SLOW TO SUBSIDE ON TUESDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR MONDAY AND TUESDAY. WEDNESDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED ON THE AREA WATERS. WINDS WILL BE OUT OF THE WEST AROUND 10 TO 15 KNOTS.
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&& .FIRE WEATHER...
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AFTER COORDINATION WITH STATE FIRE OFFICIALS THIS AFTERNOON, A FIRE WEATHER WATCH HAS BEEN ISSUED FOR SATURDAY LATE AFTERNOON AND EARLY EVENING THAT INCLUDES NE PA AND ADJACENT PORTIONS OF NW AND C NJ. THESE NRN AREAS WILL SEE GUSTY NW WINDS DEVELOP LATE IN THE AFTN BEHIND A COLD FRONT. FARTHER SOUTH TOWARD SE PA AND S NJ, THERE IS MORE UNCERTAINTY THAT THE FRONT WILL MAKE IT THAT FAR SOUTH IN TIME TO ALLOW THE GUSTY WINDS TO DEVELOP SINCE IT WILL OCCUR AFTER PEAK DAYTIME MIXING. IF THE ARRIVAL OF THE FRONT SPEEDS UP, THEN HEADLINES MAY NEED TO BE EXPANDED FARTHER SOUTH. CONDITIONS WILL BE DRY ACROSS ALL OF THE FORECAST AREA WITH MINIMUM RH VALUES ARE FORECAST IN THE 20 TO 30 PERCENT RANGE AND FUEL MOISTURE BELOW 10 PERCENT.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY EVENING FOR PAZ054-055-060>062-103-105-106. NJ...FIRE WEATHER WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY EVENING FOR NJZ001-007>010-012-013-015. DE...NONE. MD...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...MEOLA NEAR TERM...KLEIN SHORT TERM...KLEIN LONG TERM...MEOLA AVIATION...KLEIN/MEOLA MARINE...KLEIN/MEOLA FIRE WEATHER...KLEIN

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