Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 210107 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 907 PM EDT SUN JUL 20 2014 .SYNOPSIS... A WEAK AREA OF LOW PRESSURE LOCATED OFF THE MID ATLANTIC COAST WILL CONTINUE TO GRADUALLY MOVE OUT TO SEA TONIGHT. HIGH PRESSURE IS EXPECTED TO ESTABLISH ITSELF OVER OUR REGION FOR MONDAY THROUGH WEDNESDAY. A COLD FRONT IS ANTICIPATED TO ARRIVE THURSDAY, WITH HIGH PRESSURE FOLLOWING FOR FRIDAY AND SATURDAY. A WARM FRONT IS THEN FORECAST TO APPROACH FROM THE SOUTH ON SUNDAY. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... A WEAK SURFACE LOW WILL CONTINUE TO MOVE FARTHER AWAY FROM OUR COASTLINE. MEANWHILE, SURFACE HIGH PRESSURE REMAINS CENTERED NEAR NOVA SCOTIA HOWEVER IT IS WEDGED BACK DOWN OVER OUR AREA. THE COMBINATION OF THESE TWO ARE MAINTAINING AN ONSHORE FLOW. THE 00Z STERLING, VA RAOB SHOWS A VEERING WIND IN THE LOWER LEVELS ALTHOUGH SPEEDS ARE AT OR BELOW 10 KNOTS. THERE IS ALSO AN INVERSION JUST ABOVE 800 MB AND THIS MAY LOWER SOME OR ANOTHER INVERSION DEVELOPS OVERNIGHT AS THE BOUNDARY LAYER CONTINUES TO COOL. THERE IS ENOUGH MOISTURE IN THE LOWER LEVELS TO KEEP CLOUDS AROUND THROUGH THE NIGHT, HOWEVER THE CHALLENGE IS THE EXTENT OF LOW CLOUDS. AS OF NOW, DID IMPROVE THE SKY COVER FOR AT LEAST THE INTERSTATE 95 CORRIDOR AREA FOR A TIME THIS EVENING AS CLOUDS HAVE THINNED OUT QUITE A BIT. THEREAFTER, SOME CLOUDS SHOULD OCCUR AS THE MOISTURE SPREADS OUT UNDER AN INVERSION. AS OF NOW, DID NOT HIT THE LOW CLOUDS REAL HARD AND FOG WAS NOT MENTIONED GIVEN IT WILL PROBABLY BE LOCALIZED AND NOT REALLY HAVE AN IMPACT. A WEAKENING UPPER-LEVEL TROUGH AXIS REMAINS TO WELL OUR WEST ALONG WITH A SURFACE TROUGH REFLECTION. THERE HAS BEEN SOME SHOWERS WELL TO OUR WEST WITHIN AN AXIS OF INSTABILITY AND JUST ENOUGH LIFT, HOWEVER WE ARE ANTICIPATING A DRY OVERNIGHT. SOME LINGERING SHOWERS CONTINUE TO SLOWLY PIVOT AWAY FROM OUR CENTRAL COASTAL WATERS ATTM ASSOCIATED WITH THE DEPARTING SURFACE LOW. NO MAJOR CHANGES WERE MADE TO THE LOW TEMPERATURES, HOWEVER THE HOURLY GRIDS WERE ADJUSTED TO SHOW WARMER TEMPERATURES WELL INLAND THUS FAR AND A QUICKER DROP CLOSER TO THE COAST WITH THE ONSHORE FLOW. THE LAMP/LAV GUIDANCE WAS BLENDED IN TO HELP ASSIST. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... A WEAK EASTERLY FLOW WILL MAINTAIN ITSELF THROUGH MOST OF MONDAY AS HIGH PRESSURE NUDGES ITSELF INTO THE AREA FROM THE NORTHEAST. THE FLOW WON`T BE TOO STRONG...AND A BOUNDARY MOVING TOWARD THE REGION FROM THE WEST COULD TOUCH OFF A FEW SHOWERS OR EVEN A THUNDERSTORM IN WESTERN SECTIONS OF THE CWA DURING THE AFTERNOON HOURS. SO HAVE KEPT POPS IN THE SLIGHT CHANCE CATEGORY IN EASTERN PA FOR NOW. HIGHS WILL RANGE GENERALLY IN THE LOW TO MID 80S, EXCEPT IN THE UPPER 70S IN THE SOUTHERN POCONOS...AND RIGHT ALONG THE COAST WITH AN EASTERLY FLOW AND SEABREEZE. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... A BIT OF RIDGING FROM THE WEST AND SOUTH IS EXPECTED IN THE MID LEVELS FOR MONDAY NIGHT AND TUESDAY. THE SURFACE FLOW IS FORECAST TO SETTLE INTO THE SOUTHEAST AND SOUTH AT THAT TIME BRINGING AN INCREASE IN HUMIDITY. HIGH TEMPERATURES SHOULD GET INTO THE UPPER 80S IN MUCH OF OUR REGION ON TUESDAY AFTERNOON. A FEW SPOTS MAY HIT 90. CONDITIONS ARE FORECAST TO REMAIN MARGINALLY STABLE ON THE COASTAL PLAIN. HOWEVER, THERE MAY BE ENOUGH INSTABILITY IN EASTERN PENNSYLVANIA AND NORTHERN NEW JERSEY TO RESULT IN ISOLATED THUNDERSTORMS ON TUESDAY AFTERNOON. TUESDAY NIGHT IS EXPECTED TO BE RATHER MUGGY WITH NO PRECIPITATION. MINIMUM TEMPERATURES ARE ANTICIPATED TO BE MOSTLY IN THE UPPER 60S AND LOWER 70S. WEDNESDAY SHOULD BE THE HOTTEST DAY OF THE LONG TERM FORECAST PERIOD. TEMPERATURES AT THE 850 HPA LEVEL ARE EXPECTED TO RISE AROUND 18C. WE WILL CONTINUE TO CARRY MAXIMUM TEMPERATURES MOSTLY IN THE LOWER 90S WITH PEAK HEAT INDEX VALUES MAINLY IN THE MIDDLE 90S. IT WILL BE COOLER THAN THAT IN THE ELEVATED TERRAIN UP NORTH AND IN AREAS ALONG THE COAST. WE WILL CONTINUE TO MENTION A CHANCE OF THUNDERSTORMS MOVING INTO OUR REGION FROM THE NORTHWEST ON WEDNESDAY. MIXED LAYER CAPE VALUES ARE EXPECTED TO RISE AROUND 2000 J/KG FROM THE INTERSTATE 95 CORRIDOR NORTHWESTWARD IN THE AFTERNOON. HOWEVER, A BIT OF A CAP MAY INITIALLY PREVENT THE ACTIVITY FROM BECOMING WIDESPREAD. A COLD FRONT APPROACHING FROM THE NORTHWEST IS FORECAST TO BE ACROSS THE EASTERN GREAT LAKES AND THE OHIO RIVER VALLEY ON WEDNESDAY EVENING. THE BOUNDARY WILL PROGRESS SLOWLY TO THE SOUTHEAST AND IT SHOULD ARRIVE IN OUR REGION ON THURSDAY MORNING. THE FRONT MAY TAKE A GOOD PART OF THE DAY ON THURSDAY TO WORK ITS WAY THROUGH EASTERN PENNSYLVANIA, NEW JERSEY AND THE UPPER DELMARVA. WE WILL CONTINUE TO MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS FOR WEDNESDAY NIGHT AND THURSDAY. HIGH TEMPERATURES ON THURSDAY SHOULD RANGE FROM THE UPPER 70S IN THE NORTH TO NEAR 90 IN THE SOUTH. A MID LEVEL TROUGH OVER THE NORTHEASTERN STATES ON FRIDAY SHOULD LIFT TO THE NORTHEAST WITH ANOTHER TROUGH EXPECTED TO DROP OVER THE GREAT LAKES REGION ON SUNDAY. HIGH PRESSURE AT THE SURFACE IS ANTICIPATED TO BUILD ACROSS OUR REGION FOR FRIDAY AND SATURDAY WITH A WARM FRONT APPROACHING FROM THE SOUTH ON SUNDAY. DAYTIME HIGHS ARE EXPECTED TO BE MAINLY IN THE 80S WITH OVERNIGHT LOWS GENERALLY IN THE 60S. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...VFR/MVFR CEILINGS AT AND AROUND KMIV AND KACY SHOULD DEVELOP INLAND AT LEAST SOME OVERNIGHT. THERE IS LESS CONFIDENCE IF THE MVFR CEILINGS OCCUR AT ALL OF THE TERMINALS AND HOW LOW THEY GET. HOWEVER, WE STILL DEVELOP AND LOWERED THE CEILING SOME THROUGH THE NIGHT GIVEN THE ONSHORE FLOW AND ENOUGH LOW-LEVEL MOISTURE BENEATH AN INVERSION. SOME LOCAL IFR CONDITIONS ARE POSSIBLE, ESPECIALLY FOR THE KMIV AND KACY AREAS. SOME LOCAL MVFR FOG MAY OCCUR AS WELL LATE. EAST-NORTHEAST WINDS NEAR 5 KNOTS. MONDAY...ANY MVFR CEILINGS ARE EXPECTED TO IMPROVE TO VFR IN THE MORNING. EASTERLY WINDS SHOULD BECOME MORE SOUTH-SOUTHEAST DURING THE DAY NEAR 10 KNOTS. A SHOWER OR THUNDERSTORM COULD APPROACH THE KABE AND KRDG AREAS IN THE AFTERNOON, HOWEVER THESE LOOK ISOLATED. OUTLOOK... MONDAY NIGHT AND TUESDAY...MAINLY VFR. A SLIGHT CHANCE OF AFTERNOON THUNDERSTORMS FROM KILG, KPHL AND KTTN NORTHWESTWARD. TUESDAY NIGHT AND WEDNESDAY...MAINLY VFR. POSSIBLE LATE NIGHT AND EARLY MORNING MVFR OR IFR CONDITIONS IN LOW CLOUDS, FOG AND HAZE. A CHANCE OF AFTERNOON THUNDERSTORMS. WEDNESDAY NIGHT AND THURSDAY...MVFR AND IFR CONDITIONS AT TIMES IN SHOWERS AND THUNDERSTORMS. THURSDAY NIGHT AND FRIDAY...MAINLY VFR. && .MARINE... THE OFFSHORE LOW IN COMBINATION WITH THE HIGH TO THE NORTH HAS GENERATED ENOUGH WIND AND ONSHORE FETCH TO MAINTAIN SEAS OFFSHORE NEAR 6 FEET. THE BUOY DATA IS SPARSE, HOWEVER GIVEN THE SEAS AT BUOY 44009 WE EXTENDED THE SMALL CRAFT ADVISORY FOR THE OCEAN ZONES THROUGH 04Z TONIGHT. IT MAY END UP BEING MARGINAL UP NORTH, HOWEVER DID NOT WANT TO SPLIT ENDING TIMES GIVEN LITTLE DATA THERE. AS THE LOW CONTINUES TO MOVE AWAY FROM THE REGION OVERNIGHT, THE SEAS ARE EXPECTED TO SUBSIDE /ALTHOUGH COULD SEE THE SEAS HOLDING UP LONGER ACROSS THE SOUTHERN WATERS/ WITH SUB-ADVISORY CONDITIONS ANTICIPATED OVERNIGHT AND MONDAY. OUTLOOK... MONDAY NIGHT THROUGH FRIDAY...NO MARINE HEADLINES ARE ANTICIPATED. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ450>455. && $$ SYNOPSIS...GORSE/IOVINO NEAR TERM...GORSE SHORT TERM...MIKETTA LONG TERM...IOVINO AVIATION...GORSE/IOVINO MARINE...GORSE/IOVINO

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