Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 041430 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1030 AM EDT FRI SEP 4 2015 .SYNOPSIS... A BACKDOOR COLD FRONT WILL MOVE ACROSS OUR AREA THIS MORNING. HIGH PRESSURE WILL THEN BUILD INTO OUR REGION FROM THE NORTH SATURDAY INTO SUNDAY BEFORE MOVING OFFSHORE EARLY NEXT WEEK. A COLD FRONT IS SCHEDULED TO APPROACH LATE WEDNESDAY, THEN MOVE THROUGH OUR REGION DURING THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A BACKDOOR COLD FRONT WAS LOCATED NEAR THE CENTRAL MD AND CENTRAL PA BORDER STRETCHING SOUTHEASTWARD TOWARD THE CHESAPEAKE BAY BUT THE BOUNDARY WAS RATHER DIFFUSE. NORTHEAST WINDS ARE OCCURRING BEHIND THE FRONT. THERE WAS ALSO AN AREA OF STRATOCU MOVING INTO CENTRAL AND NORTHWEST NJ, WHICH SHOULD ADVECT SOUTHEASTWARD THRUOUT THE DAY. THE HEART OF THE COOLER AND DRIER AIR LAGS BEHIND THE FRONT ITSELF AND IS CURRENTLY STILL BACK IN SOUTHEAST NEW ENGLAND. THEREFORE, LOCATIONS AWAY FROM THE COAST WILL STILL BE HOT AND HUMID TODAY...AT LEAST FOR SEPTEMBER STANDARDS...BUT NOT NEARLY AS HOT AS THE REST OF THE WORK WEEK WAS. LATEST GUIDANCE HAS THE POST- FRONTAL COOLER AIR THAT IS CURRENTLY OVER NEW ENGLAND ARRIVING IN CONJUNCTION WITH A EAST TO NORTHEASTERLY WIND SURGE DURING THE EARLY TO MID AFTERNOON IN NORTHERN AND CENTRAL NJ AND MID TO LATE AFTERNOON FOR THE DELAWARE VALLEY. BUMPED UP MAX TEMPS A COUPLE OF DEGREES ACROSS ROUGHLY THE SOUTHWESTERN HALF OF THE CWA GIVEN THE LATER ARRIVAL OF THE COOLER AIR. A FEW WARM SPOTS SUCH AS ESN, ILG AND PHL HAVE A SHOT AT REACHING 90F TODAY, BUT MOST OF THE AREA WILL BE IN THE 80S (EXCEPT 70S ALONG THE COAST AND IN THE POCONOS). THERE IS A WEAK MID-LEVEL SHORTWAVE TROUGH NEAR NYC WILL DROP SOUTHWESTWARD THRU THE AREA TODAY. THIS COULD PROVIDE LIFT FOR CONVECTION THIS AFTERNOON. HIRES GUIDANCE CONTINUES TO PINPOINT EASTERN PA AND EASTERN MD FOR THE HIGHEST COVERAGE OF SHOWERS AND STORM THIS AFTERNOON, WHICH MAKES SENSE GIVEN THE RIDGE OF HIGHER INSTABILITY WILL BE POSITIONED OVER OUR WESTERN MOST ZONES. SHOWERS AND STORMS WILL LIKELY COINCIDE WITH PEAK HEATING HOURS AND COVERAGE WILL BE SCATTERED IN OUR FAR WESTERN ZONES. MEANWHILE, CONVECTION OVER THE DELAWARE VALLEY MAY BE MORE ISOLATED AND OCCUR EARLIER IN THE AFTERNOON JUST BEFORE THE STABLE AIR ARRIVES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... AS THE CENTER OF HIGH PRESSURE DROP FROM QUEBEC INTO NEW ENGLAND FOR TONIGHT, DRY AIR WILL CONTINUE TO PUSH INTO OUR REGION. SOME CLEARING IS EXPECTED FROM THE NORTHEAST AND ANY CHANCE OF PRECIPITATION WILL BE PUSHED TO THE SOUTHWEST AND SOUTH OF OUR FORECAST AREA. THE WIND WILL REMAIN FROM THE NORTHEAST FOR TONIGHT AND TEMPERATURES SHOULD DROP INTO THE 60S AT MOST LOCATIONS. READINGS ARE ANTICIPATED TO FALL INTO THE UPPER 50S IN THE POCONO REGION AND IN FAR NORTHERN NEW JERSEY. && .LONG TERM /SATURDAY THROUGH THURSDAY/... THE SYNOPTIC SETUP IS COMPRISED OF A RIDGE ACROSS THE EAST AND A TROUGH IN THE WEST. AS THE TROUGH EJECTS EASTWARD ACROSS THE NORTHERN PLAINS AND MIDWEST SUNDAY INTO MONDAY, THE PORTION OF THE RIDGE IN THE NORTHEAST AND MID ATLANTIC IS FORECAST TO FLATTEN. THE TROUGH OR ANOTHER ONE BEHIND IT GRADUALLY SLIDES EAST- NORTHEAST THROUGH THURSDAY, HOWEVER THE RIDGE WHILE GETTING PUSHED SOUTHEASTWARD IT TENDS TO SLOW THE EASTWARD PROGRESSION OF THE INCOMING SYSTEM. THIS PATTERN TENDS TO FAVOR WARMTH AND DRYNESS ALTHOUGH A BREAK OCCURS SATURDAY INTO SUNDAY IN THE WAKE OF A BACKDOOR COLD FRONT. THE REGION NEEDS RAIN, HOWEVER IT LOOKS LIKE THE CHCS ARE RATHER LOW GIVEN NO ORGANIZED SYSTEMS MOVING THROUGH. WE USED A MODEL/CONTINUITY BLEND FOR SATURDAY INTO MONDAY, WITH A 00Z WPC GUIDANCE/CONTINUITY BLEND THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE AFTER ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR SATURDAY AND SUNDAY...AS THE UPPER-LEVEL RIDGE CRESTS ACROSS THE AREA, SURFACE HIGH PRESSURE SHOULD EASE EASTWARD. THIS WILL ALLOW THE ONSHORE FLOW TO WEAKEN AND EVENTUALLY TURN SOUTHERLY. THE ONSHORE FLOW HOWEVER PERSISTS SATURDAY WITH ENOUGH MOISTURE TO RESULT IN MORE CLOUDINESS FOR A TIME ACROSS THE SOUTHERN ZONES. SOME GUIDANCE SHOWS SOME LIGHT QPF IN PORTIONS OF MARYLAND AND CENTRAL/SOUTHERN DELAWARE, HOWEVER THIS IS OF LOWER CONFIDENCE GIVEN THE SURFACE HIGH BUILDING SOUTHWARD. AS A RESULT, WE WENT WITH A DRY FORECAST BUT DID CARRY MORE CLOUD COVER. A MUCH COOLER DAY IS EXPECTED SATURDAY DUE TO THE ONSHORE FLOW. WE START TO LOSE THE STRENGTH OF THE ONSHORE FLOW SUNDAY, AND THEREFORE THE DAYTIME TEMPERATURES ARE ANTICIPATED TO START REBOUNDING IN THE AFTERNOON FOR MUCH OF THE AREA. THIS WILL BE MORE ACROSS THE INTERIOR COMPARED TO THE COASTAL LOCALES. FOR MONDAY AND TUESDAY...AN UPPER-LEVEL TROUGH TO CLOSED LOW TRACKING FROM THE NORTHERN PLAINS INTO SOUTH-CENTRAL CANADA IS FORECAST TO ALLOW FOR A FLATTER RIDGE IN THE EAST. THIS WILL ALSO FORCE HIGH PRESSURE MORE OFFSHORE, AND A WEAK COLD FRONT SHOULD BE GRADUALLY SLIDING EASTWARD ACROSS THE GREAT LAKES. THE BULK OF THE ENERGY IS FORECAST TO TRACK INTO CANADA TUESDAY, THEREFORE THE CHCS FOR CONVECTION IS EXPECTED TO BE TO OUR WEST. AS THE FLOW IS MORE SOUTHERLY, A RATHER WARM AIRMASS LOOKS TO BE IN PLACE WITH SOME INCREASE IN THE DEW POINTS EACH DAY. THERE IS A WEAK SYSTEM FORECAST TO BE OFF OF THE COAST OF THE CAROLINAS, HOWEVER MOISTURE ASSOCIATED WITH THAT SHOULD REMAIN TO OUR SOUTH GIVEN SURFACE HIGH PRESSURE CLOSER TO OUR AREA. FOR WEDNESDAY AND THURSDAY...SOME GUIDANCE SUGGESTS THE TROUGH TO CLOSED LOW IS FOLLOWED BY A SHORT WAVE TROUGH FROM THE MIDWEST TO THE GREAT LAKES. THIS MAY INDUCE A WEAK SURFACE LOW ALONG THE COLD FRONT, SLOWING IT DOWN SOME MORE. THE COMBINATION OF THIS ALONG WITH THE INITIAL ENERGY TRACKING WELL NORTH AND THE RIDGE FARTHER SOUTH SHOULD RESULT IN A SLOWER FRONTAL PASSAGE. THIS TIMING WILL GOVERNOR THE PROSPECTS FOR THE CONVECTIVE CHCS, HOWEVER THE WPC GUIDANCE SHOWS THE SURFACE FRONT MOVING IN DURING THURSDAY. THIS SHOULD EXTEND THE PERIOD OF RATHER WARM CONDITIONS, HOWEVER THE ARRIVAL OF THE FRONT ON THURSDAY MAY SIGNAL A CHANGE. OVERALL, LOW POPS ARE CARRIED MOSTLY THURSDAY AS THE FRONT ARRIVES. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VSBYS ARE CURRENTLY 5SM IN HZ AT ACY AND ILG, BUT SHOULD IMPROVE TO VFR SHORTLY. THE REST OF THE TAF SITES ARE VFR AND EXPECT IT TO STAY THAT WAY THRU MUCH OF THE DAY. A DECK OF STRATOCUMULUS APPROACHING FROM THE NORTHEAST SHOULD OVERSPREAD OUR REGION TODAY. CEILINGS ARE FORECAST TO REMAIN ABOVE 4000 FEET. SCATTERED SHOWERS ARE POSSIBLE FROM ABOUT 1600Z UNTIL 2200Z AND THEY HAVE BEEN MENTIONED FOR ALL OF OUR TAF SITES EXCEPT KTTN AND KACY. CONDITIONS AROUND THOSE TWO TAF SITES AND POINTS TO THE NORTHEAST SHOULD REMAIN MORE STABLE THAN AT LOCATIONS TO THE SOUTHWEST. ALSO, THERE IS THE POTENTIAL FOR ISOLATED THUNDERSTORMS MAINLY IN EASTERN PA BUT THE RISK IS NOT HIGH ENOUGH TO INCLUDE IN THE TAFS. THE STRATOCUMULUS IS EXPECTED TO LOWER THIS EVENING WITH MVFR CEILINGS POSSIBLE THRU MUCH OF THE NIGHT. THE WIND IS ANTICIPATED TO FAVOR THE NORTHEAST AND EAST THROUGH THE TAF PERIOD AT SPEEDS FROM ABOUT 6 TO 12 KNOTS. OUTLOOK... SATURDAY AND SUNDAY...VFR OVERALL, HOWEVER SOME CLOUDINESS IS POSSIBLE SATURDAY MAINLY SOUTH OF KILG TO KACY. LOCALIZED FOG POSSIBLE LATE SATURDAY NIGHT AND EARLY SUNDAY MORNING. EAST- NORTHEAST WINDS 10-15 KNOTS SATURDAY /STRONGEST CLOSER TO THE COAST/, DIMINISHING SOME AND BECOMING SOUTHEASTERLY SUNDAY. MONDAY AND TUESDAY...VFR OVERALL. SOUTHERLY WINDS LESS THAN 10 KNOTS.
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&& .MARINE... HIGH PRESSURE WILL BUILD SOUTHWARD FROM QUEBEC TODAY AND INTO NEW ENGLAND TONIGHT. AN INCREASING NORTHEAST FLOW IS EXPECTED AND WIND GUSTS SHOULD INCREASE TO AROUND 25 KNOTS DURING THE AFTERNOON. AS A RESULT, WE HAVE A SMALL CRAFT ADVISORY IN EFFECT FOR ALL BUT THE UPPER PART OF DELAWARE BAY WHICH SHOULD BE SHELTERED FROM THE STRONGEST OF THE GUSTS. THE SMALL CRAFT ADVISORY BEGINS AT NOON FOR OUR NORTHERN WATERS AND AT 400 PM FOR OUR SOUTHERN WATERS AND FOR LOWER DELAWARE BAY. WAVE HEIGHTS ON OUR OCEAN WATERS ARE ANTICIPATED TO BUILD TO 4 TO 6 FEET FOR LATE TODAY INTO TONIGHT. WAVE HEIGHTS SHOULD BUILD TO 2 TO 4 FEET ON LOWER DELAWARE BAY AND 1 TO 2 FEET ON THE UPPER BAY. OUTLOOK... SATURDAY...EAST-NORTHEAST WINDS ARE EXPECTED TO GRADUALLY DIMINISH FROM NORTH TO SOUTH AS HIGH PRESSURE BUILDS CLOSER. HOWEVER, STRONG ENOUGH FLOW WITHIN A TIGHTENED PRESSURE GRADIENT WILL RESULT IN WIND GUSTS TO AROUND 25 KNOTS FOR AWHILE MAINLY ON THE ATLANTIC COASTAL WATERS. IT COULD BE CLOSE MAINLY IN THE MORNING FOR LOWER DELAWARE BAY, HOWEVER AS OF NOW DID NOT TAKE THE SMALL CRAFT ADVISORY BEYOND 12Z GIVEN LOWER CONFIDENCE. THE SEAS OF 4-6 FEET ARE EXPECTED ON THE ATLANTIC COASTAL WATERS AS A RESULT OF THE STRONGER ONSHORE FLOW, HOWEVER THESE SHOULD BE SUBSIDING THROUGH THE NIGHT. SUNDAY THROUGH TUESDAY...THE WINDS ARE ANTICIPATED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA AS THEY SHIFT FROM EAST-NORTHEAST TO SOUTHEAST AND SOUTH. THE SEAS ARE CURRENTLY ANTICIPATED TO BE BELOW 5 FEET. && .RIP CURRENTS... THE THREAT FOR DANGEROUS RIP CURRENTS WILL BE ENHANCED FOR TODAY AND THE UPCOMING LABOR DAY WEEKEND. A DEVELOPING AND INCREASING NORTHEAST TO EAST WIND IS EXPECTED ALONG THE COASTS OF NEW JERSEY AND DELAWARE FOR TODAY. THE STRENGTHENING ONSHORE FLOW WILL RESULT IN A MODERATE RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS. FOR SATURDAY AND SUNDAY, THE WINDS AND WAVES ALONG THE COAST SHOULD GRADUALLY SUBSIDE LATE SATURDAY INTO SUNDAY. AS OF NOW, IN- HOUSE GUIDANCE IS SUGGESTING A SOLID MODERATE /POSSIBLY NEARING HIGH/ FOR SATURDAY. THE RISK SHOULD LOWER SOME SUNDAY BUT IT MAY STILL BE MODERATE. IT IS PARTICULARLY IMPORTANT FOR SAFETY AWARENESS TO SHARE THIS INFORMATION TO BEACHGOERS AND LIFEGUARDS WITH THE BEACH CROWD ANTICIPATED TO BE LARGER THAN NORMAL GIVEN IT IS LABOR DAY WEEKEND. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 PM EDT SATURDAY FOR ANZ452>455. SMALL CRAFT ADVISORY UNTIL 6 PM EDT SATURDAY FOR ANZ450-451. SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 8 AM EDT SATURDAY FOR ANZ431.
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&& $$ SYNOPSIS...GORSE NEAR TERM...KLEIN SHORT TERM...IOVINO LONG TERM...GORSE AVIATION...GORSE/IOVINO/KLEIN MARINE...GORSE/IOVINO RIP CURRENTS...GORSE/IOVINO/KLEIN

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