Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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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/...
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.

&&

.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/...
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.

&&

.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...
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.

&&

$$
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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