Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 230059 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 859 PM EDT FRI APR 22 2016 .SYNOPSIS... A SLOW MOVING COLD FRONT ENTERING NORTHWEST PENNSYLVANIA WILL MOVE OFF THE MID ATLANTIC COAST SATURDAY MORNING. CANADIAN HIGH PRESSURE WILL SETTLE SOUTHEAST INTO THE MID ATLANTIC STATES SUNDAY. A COLD FRONT WILL EXTEND EAST FROM THE MIDWEST TO SOUTHERN NEW ENGLAND MONDAY THEN EDGE SOUTH THROUGH THE MID ATLANTIC STATES TUESDAY. CANADIAN HIGH PRESSURE IS FORECAST TO PUSH THE FRONT JUST SOUTH OF OUR AREA WEDNESDAY. LOW PRESSURE IN THE MIDWEST THURSDAY WILL HEAD FOR THE MID ATLANTIC STATES AND EVENTUALLY MOVE OUT TO SEA LATER FRIDAY. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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A COLD FRONT MOVING ACROSS PA ATTM WILL CROSS OUR FORECAST AREA OVER THE NEXT 6 HOURS. SCT SHOWERS AND PERHAPS A RUMBLE OF THUNDER EXPECTED. WINDS WILL SHIFT TO NW OR N OVERNIGHT AS THE FRONT PASSES THE AREA. GRIDS UPDATED WITH SLIGHTLY SLOWER FROPA TIMING. LOW TEMPS AND OTHER GRIDS LOOKED OK OVERALL.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... GENERALLY, MODELS SEEM TO HAVE CONVERGED TOWARD A SIMILAR SOLUTION WITH TODAY`S 12Z RUN, SHOWING THE VORT MAX AT BASE OF H5 SHORTWAVE TROUGH MOVING ACROSS THE DC AREA IN MORNING AND THEN OFF THE DELMARVA COAST DURING THE AFTERNOON. A SLOWER SOLUTION WAS FAVORED WRT THE EXIT OF THE SHORTWAVE TROUGH AND COLD FRONT SINCE THERE HAS BEEN A PERPETUAL PROGRESSIVE BIAS IN THE MODELS WITH THIS SYSTEM EVER SINCE IT WAS A CUTOFF LOW OVER THE SWRN US LAST WEEKEND. ACCORDINGLY, SHOWERS ASSOCIATED WITH THE REMNANT UPPER LOW MAY PERSIST OVER THE DELMARVA AND SRN NJ THRU THE MORNING AND POSSIBLY LINGER INTO THE EARLY AFTERNOON. OTHERWISE, NWLY FLOW BEHIND THE FRONT WILL ADVECT DRIER AND COOLER AIR INTO THE REGION. SKIES WILL CLEAR ACROSS THE POCONOS INITIALLY DURING THE MORNING AND EXPAND S/E TOWARD THE I-95 CORRIDOR AROUND MIDDAY AND S NJ/DE COAST LATE IN THE AFTERNOON. CAA IN THE BOUNDARY LAYER APPEARS TO BE MODEST AND CERTAINLY NOT STRONG ENOUGH TO COMPLETELY OFFSET DAYTIME INSOLATION WITH A HIGH SUN ANGLE THIS TIME OF YEAR. THUS, HIGHS SHOULD STILL BE AT OR EVEN A FEW DEGREES ABOVE NORMAL, RANGING FROM THE UPPER 50S AT MT POCONO TO AROUND 70F IN PHILADELPHIA. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... 500MB: THE PATTERN IN THIS LONG TERM SECTION IS CHARACTERIZED BY A STRONGLY NEGATIVE NAO. A SHORT WAVE CROSSES THE NORTHEAST MONDAY NIGHT/TUESDAY, ANOTHER LATE THURSDAY INTO FRIDAY. TEMPERATURES: THE FIRST 21 DAYS OF APRIL HAVE AVERAGED NEAR NORMAL AT PHL, TTN AND ABE AND 1-2 TO DEGREES BELOW NORMAL ELSEWHERE. CALENDAR DAY AVERAGES SHOULD AVERAGE SEVERAL DEGREES BELOW NORMAL SUNDAY, SEVERAL DEGREES ABOVE NORMAL MONDAY AND TUESDAY, NEAR OR SLIGHTLY BELOW NORMAL WEDNESDAY. THURSDAY AND FRIDAY ARE MORE UNCERTAIN BUT LETS SAY FOR NOW, WITHIN 5 DEGREES EITHER SIDE OF NORMAL. FORECAST BASIS: UNLESS OTHERWISE NOTED, A 50 50 BLEND OF THE 12Z/22 GFS/NAM MOS GUIDANCE SATURDAY NIGHT-SUNDAY NIGHT, THEREAFTER THE 12Z/22 GFS MEX MOS FOR MONDAY AND MONDAY NIGHT AND WPC GUIDANCE TUESDAY - FRIDAY. ONE NOTABLE EXCEPTION... SINCE THERE IS SO MUCH UNCERTAINTY TUESDAY REGARDING THE POSITION OF A STRONG COLD FRONT... HAVE BLENDED THE MUCH COOLER ECMWF 12Z 2M TEMPS TUESDAY WITH THE WPC GUIDANCE TO FORECAST A SIGNIFICANT COOLING NE PA AND MUCH OF NNJ. THE DAILIES... SATURDAY NIGHT...CLEAR AND CHILLY WITH FROST POTENTIAL LATE (7Z- 11Z)NEAR AND NW OF I-78. LIGHT NORTH FLOW EXCEPT POSSIBLE GUSTS 15 MPH ALONG THE COASTS. RADIATIONAL COOLING MOST IDEAL LATE AT NIGHT. LOWERED 12Z/22 NCEP BLENDED GUIDANCE 2-3 DEGS IN THE COUNTRYSIDE NORTHWEST OF I-95. SCT FROST IS IN THE FCST WHERE ANTICIPATE THE NEED FOR A FROST ADVISORY IN A FUTURE ISSUANCE WHICH IS BASICALLY NEAR AND N OF I-78. LOWS ABOUT 4 TO 8 DEGREES BELOW NORMAL. SUNDAY...SUNNY AND PLEASANT. LIGHT NORTH TO NORTHWEST WIND BACKING TO SOUTHWEST LATE IN THE DAY. NEAR NORMAL MAX TEMPS. MONDAY...PARTLY TO MOSTLY SUNNY AND WARMER... GOOD WEATHER. SW WIND GUST 20 TO 25 MPH IN THE AFTERNOON. MAX TEMPS ABOUT 10 DEGREES ABOVE NORMAL AWAY FROM THE MARINE INFLUENCE. THERE IS A SMALL CHANCE THAT WE WILL HAVE FIRE WEATHER CONCERNS ACROSS E PA AND NJ MONDAY AFTERNOON. TUESDAY...CONSIDERABLE UNCERTAINTY BUT FOR NOW MORNING MIN TEMPERATURES ABOUT 10 TO 15 DEGREES ABOVE NORMAL KRDG-KPHL-KACY SOUTH WHILE A SHOWERY ACTIVE COLD FRONT SEEPS SOUTHWARD BY DAYBREAK, MAYBE TO NEAR I-78. HOPEFULLY BENEFICIAL RAINFALL. CHANCE OF A THUNDERSTORM PHILLY AREA SOUTHWARD. WEST WIND SHIFT TO NORTH OR NORTHEAST AND POSSIBLY GUSTY 20 MPH. LOW TEMPERATURE FOR THE CALENDAR DAY NEAR 1 AM WEDNESDAY WITH MOST MAX TEMPS FOR THIS CALENDAR DAY POSSIBLY OCCURRING PRIOR TO 18Z/26. AS IT MODELS NOW, CONSIDERABLE ERROR POTENTIAL FOR THE MORNING MIN TEMPS AND DAYTIME MAX TEMPS. TUESDAY NIGHT...CONSIDERABLE CLOUDINESS AS ANY LINGERING SHOWERS END EARLY. COOL. IF IT CLEARS SOON ENOUGH, THERE COULD BE A FROST CONCERN IN NW NJ AND NE PA. WEDNESDAY...BECOMING MOSTLY SUNNY AND PLEASANT. LIGHT WIND. THURSDAY...LOOKS LIKE RAINY OR SHOWERY WITH CONSIDERABLE UNCERTAINTY REGARDING TEMPERATURES. BIG ERROR POTENTIAL ONCE AGAIN ON DAYTIME MAX TEMPS SINCE WE`RE NOT EXACTLY SURE OF THE PATH LOW PRESSURE TAKES ACROSS THE MID ATLANTIC STATES. THAT ALSO IMPACTS THE WIND DIRECTION. WHAT WE`RE MOST CONFIDENT OF IS THAT IT WILL RAIN. FRIDAY...ANY LINGERING RAIN ENDS EARLY WITH A COOL NORTHERLY FLOW TO FOLLOW. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. AN APPROACHING COLD FRONT HAS LED TO AN INCREASE IN COVERAGE OF SHOWERS THIS EVENING. THESE SHOWERS AND LOCALLY LOWER CIGS/VSBYS EXPECTED FOR THE NEXT 6 HOURS OR SO. ONCE THE FRONT PASSES...WINDS WILL SHIFT TO NW OR N AND DRIER AIR WILL ARRIVE OVER THE AREA. CIGS WILL INCREASE SAT MORNING WITH VFR EXPECTED MUCH OF THE DAY. OUTLOOK... SATURDAY NIGHT...VFR. LIGHT NORTH WIND MAY GUST 15 KT ALONG THE COASTS. SUNDAY...VFR...FEW CIRRUS. LIGHT NORTH NORTHWEST WIND BACKING TO SOUTHWEST LATER IN THE DAY. MONDAY...VFR PATCHES OF SCT-BKN AOA 5000FT. SW WIND GUSTY 20 KT. TUESDAY...MVFR/IFR LIKELY IN SHRA/TSRA TUE AS A SLOW SOUTHWARD MOVING COLD FRONT TRAVERSES THE TERMINALS. MVFR CIGS EXPECTED TO LINGER WELL INTO TUESDAY NIGHT AFTER THE SHOWERS END. WEST WIND EARLY IN THE MORNING SHIFT GUSTY NORTH TO NORTHEAST. WEDNESDAY...VFR. LIGHT WIND.
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&& .MARINE...
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SCA FLAG FROM EARLIER WAS ALLOWED TO EXPIRE AS SEAS ON THE OCEAN AND WINDS OVERALL HAVE SLACKENED SINCE THIS AFTERNOON. SCATTERED SHOWERS EXPECTED OVERNIGHT AND SAT MORNING (SOUTHERN WATERS). OUTLOOK... SATURDAY NIGHT...NORTH-NORTHWEST WINDS MAY REACH THE SCA THRESHOLD FOR A BRIEF PERIOD OF TIME AS HIGH PRESSURE BUILDS OVER THE COASTAL WATERS. LATE MONDAY OR TUESDAY...AN SCA WILL LIKELY BE NEEDED AS BOTH WINDS AND SEAS INCREASE IN ASSOCIATION WITH LOW PRESSURE AND COLD FRONT PASSING THROUGH THE MID ATLANTIC STATES. WEDNESDAY...NO MARINE HEADLINES ANTICIPATED AT THIS TIME. LIGHT NORTH WIND TRENDING ONSHORE.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...DRAG NEAR TERM...O`HARA SHORT TERM...KLEIN LONG TERM...DRAG AVIATION...DRAG/KLEIN/O`HARA MARINE...DRAG/KLEIN/O`HARA

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