Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 031956
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
356 PM EDT THU SEP 3 2015

.SYNOPSIS...
A BACKDOOR COLD FRONT WILL PUSH ACROSS THE AREA TONIGHT INTO FRIDAY.
HIGH PRESSURE WILL BUILD ACROSS THE REGION FROM THE NORTH SATURDAY,
BEFORE MOVING OFFSHORE SUNDAY. HOWEVER, IT WILL CONTINUE AFFECT THE
AREA THROUGH EARLY NEXT WEEK. A COLD FRONT IS EXPECTED TO APPROACH
THE AREA FROM THE WEST LATE WEDNESDAY, THEN PUSH ACROSS THE AREA
AROUND THURSDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A SURFACE TROUGH CONTINUES TO SHARPEN OVER THE MID-ATLANTIC COASTAL
PLAIN, NOT TOO FAR EAST OF I-95. A SEA-BREEZE FRONT WAS WELL-DEFINED
ON DOPPLER RADAR ACROSS SOUTHERN NJ AND DE AND HAS MOVED ABOUT 15
MILES INLAND AS OF 3 PM.

DID NOT MAKE MANY CHANGES FROM THIS MORNING`S UPDATE TO THE
AFTERNOON AND EVENING POP/WX GRIDS. WE ARE HIGHLIGHTING TWO SEPARATE
FOR ISOLATED SHOWERS AND STORMS: 1)THE LOWER DELMARVA, WHERE
ENHANCED LOW-LEVEL CONVERGENCE ALONG THE TROUGH AXIS AND LOCALLY
HIGHER INSTABILITY ARE PRESENT AND 2) IN NORTHEAST PA AND NORTHWEST
NJ WELL AHEAD OF A BACKDOOR COLD FRONT WHERE THE FOCUS FOR
CONVECTION IS TERRAIN CIRCULATIONS. CONVECTION IN OUR NORTHERN ZONES
WILL BE DELAYED UNTIL LATE THIS AFTERNOON (AFTER 4 PM) AND THIS
EVENING AS UPSTREAM ACTIVITY OVER NORTH-CENTRAL PA HAS A WEAK STORM
MOTION. THE BETTER LIFT ALONG THE BACKDOOR COLD FRONT WILL REMAIN
NORTH OF THE AREA UNTIL LATE TONIGHT, LIMITED CONVECTIVE COVERAGE.

THE COLD FRONT BOUNDARY WILL START TO MOVE IN FROM THE NORTHEAST
LATE TONIGHT. DO NOT EXPECT MUCH PRECIP WITH IT OVERNIGHT AS THE
BOUNDARY LAYER STABILIZES BEFOREHAND. DEBRIS CLOUDS FROM THIS
EVENING`S CONVECTION WILL IMPACT NE PA AND NW NJ. ELSEWHERE, EXPECT
CLOUDS WILL BE MUCH MORE SCATTERED AND THE WINDS WILL RELAX THIS
EVENING, ALLOWING THE SURFACE TO RADIATE MORE EFFECTIVELY.
INCREASING CLOUDS AND A LIGHT NORTHEAST WIND WILL MOVE SOUTHWESTWARD
DURING THE EARLY MORNING AS THE FRONT APPROACHES. THIS SHOULD LIMIT
THE EXTENT OF FOG DEVELOPMENT.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
THE BACKDOOR COLD FRONT WILL CONTINUE TO PROGRESS SOUTHWESTWARD THRU
THE AREA ON FRIDAY. THERE WILL BE A LAG BETWEEN THE FROPA AND
ARRIVAL OF THE COOLER AIR. THE FORMER WILL OCCUR IN THE AFTERNOON,
WHEN HIGH PRESSURE OVER SOUTHERN QUEBEC NOSES SOUTHWARD DOWN THE
EASTERN SEABOARD. THIS PRESSURE SURGE WILL BE ACCOMPANIED BY BREEZY
E TO NE WINDS THAT WILL ADVECT COOLER AIR INTO THE AREA. THEREFORE,
THERE IS A CONSIDERABLE TEMPERATURE GRADIENT TOMORROW AFTERNOON,
RANGING FROM THE 70S ALONG THE COAST AND IN NORTHERN NJ TO NEAR 90F
IN EASTERN MD. ANOTHER REASON FOR THE LARGE TEMPERATURE GRADIENT IS
THE CLOUD COVER, WHICH WILL BE HIGHER ACROSS NJ AND NORTHEAST PA
THAN FARTHER TO THE SOUTH AND WEST.

WITH MORE STABLE MARINE AIR ADVECTING INLAND DURING THE DAY, THE
BEST CHANCE FOR SHOWERS AND STORMS WILL BE INLAND (OUT TOWARD
READING AND THE EASTERN SHORE OF THE CHESAPEAKE BAY) AND DURING THE
PEAK HEATING HOURS OF THE AFTERNOON. THE COVERAGE OF SHOWERS AND
STORMS LOOKS TO BE SCATTERED IN THESE FAR WESTERN ZONES AND MORE
ISOLATED CLOSER TO THE DELAWARE VALLEY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
ONCE THE FRONT PUSHES SOUTH OF THE AREA FRIDAY EVENING, ANY
REMAINING SHOWERS WILL MOVE SOUTH OF THE AREA OR DISSIPATE. HIGH
PRESSURE WILL THEN BUILD BACK ACROSS THE EAST COAST FROM THE NORTH
FROM SATURDAY, BEFORE IT MOVES OFFSHORE SUNDAY. THE HIGH WILL
CONTINUE TO AFFECT THE AREA THROUGH TUESDAY, WHICH WILL PROVIDE
MOSTLY DRY WEATHER ACROSS THE AREA. THERE IS SOME GUIDANCE
INDICATING THERE MAY BE SOME SHOWER ACTIVITY ON THE SOUTHERN EDGE
OF THE HIGH PRESSURE ACROSS THE SOUTHERN PORTIONS OF THE AREA OVER
THE WEEKEND INTO MONDAY. ALL INDICATIONS ARE ANY PRECIPITATION
SHOULD BE LIGHT.

ONE THING OF NOTE IS MODELS ARE INDICATING AN AREA OF LOW
PRESSURE DEVELOPING AND STRENGTHENING SLIGHTLY OFF THE SOUTHEAST
COAST OVER THE WEEKEND. THEY MOVE THIS LOW NORTHWARD, WHILE
WEAKENING IT, BUT KEEP IT OFFSHORE AS IT GETS CAUGHT UP IN THE
SOUTHWEST FLOW ALOFT BY TUESDAY. DEPENDING ON HOW CLOSE IT GETS,
THERE COULD BE SOME SCATTERED SHOWERS ACROSS THE AREA ON TUESDAY.

MODELS HAVE SLOWED DOWN A COLD FRONT, WHICH IS NOW FORECAST TO
BEGIN TO APPROACH THE AREA LATE WEDNESDAY AND MOVE ACROSS THE AREA
THURSDAY. THERE IS A SLIGHT CHANCE FOR SHOWERS TO AFFECT THE
NORTHWEST PORTIONS OF THE AREA WEDNESDAY, BUT IT LOOKS MORE LIKELY
WEDNESDAY NIGHT AND THURSDAY FOR THE POTENTIAL FOR PRECIPITATION
FOR THE REST OF THE AREA.

TEMPERATURES COOL OFF SLIGHTLY SATURDAY, FOLLOWED BY A WARMING
TREND SUNDAY THROUGH THE MIDDLE OF NEXT WEEK.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

ISOLATED SHOWERS AND STORMS COULD APPROACH ABE AND RDG BETWEEN 20-
01Z. DID NOT INCLUDE THIS IN THE TAFS DUE TO SUCH LOW CHANCES.
OTHERWISE, VFR THRU 06Z. NLY WINDS 5-10 KT THIS AFTN. THE EXCEPTION
IS ACY, WHERE WINDS ARE SELY IN WAKE OF A SEA-BREEZE FRONT. THE SEA
BREEZE WILL LIKELY MAKE IT TO MIV LATE THIS AFTN AND THEN PERHAPS
THE I-95 TERMINALS TOWARD 00Z. A BRIEF WIND SHIFT OUT OF THE SE
WOULD OCCUR.

PATCHY FOG COULD DEVELOP EARLY FRIDAY MORNING BUT A LIGHT NELY WIND
AND CLOUDS SHOULD LIMIT THE EXTENT OF IT. ONLY HAVE MVFR
RESTRICTIONS AT MIV FOR NOW.

NELY WINDS INCREASE DURING THE DAY FRIDAY BEHIND A FRONT TO AROUND
10 KT.

OUTLOOK...

FRIDAY NIGHT-TUESDAY NIGHT...MOSTLY VFR. GUSTY E-NE WINDS AROUND 15-
20 KNOTS SATURDAY AFTERNOON. PATCHY FOG/STRATUS POSSIBLE AROUND
DAYBREAK EACH DAY.

&&

.MARINE...
NO HAZARDS ON THE MARINE ANTICIPATED THRU FRIDAY MORNING. NELY
WINDS WILL INCREASE THOUGH DURING THE DAY FRIDAY AND SCA
CONDITIONS ARE LIKELY TO DEVELOP LATER THAT AFTERNOON IN OUR
NORTHERN ZONES WITH 15- 20 KT WINDS (GUSTS TO 25 KT) AND SEAS OF
4-5 ARE FORECAST TO ARRIVE.

OUTLOOK...

FRIDAY NIGHT-SATURDAY NIGHT...SEAS REMAIN ABOVE SMALL CRAFT
ADVISORY LEVELS WITH THE EASTERLY FETCH BEHIND THE BACKDOOR COLD
FRONT FRIDAY NIGHT INTO SATURDAY. WINDS REMAIN ABOVE SMALL CRAFT
ADVISORY LEVELS BEHIND THE BACKDOOR COLD FRONT AS WELL FRIDAY
NIGHT INTO SATURDAY.

SUNDAY-TUESDAY NIGHT...SEAS EXPECTED TO SUBSIDE BACK BELOW SMALL
CRAFT ADVISORY CONDITIONS BY SUNDAY. WINDS AND SEAS THEN EXPECTED TO
REMAIN BELOW SMALL CRAFT ADVISORY LEVELS THROUGH TUESDAY NIGHT.

&&

.RIP CURRENTS...
THE THREAT FOR DANGEROUS RIP CURRENTS WILL BE ENHANCED FRIDAY AND
THE UPCOMING LABOR DAY WEEKEND. NORTHEASTERLY WINDS SURGE BEHIND
A BACKDOOR COLD FRONT OF 10 TO 15 KT WILL ARRIVE FRIDAY MORNING
AND INCREASE TO 15-20 KT FRIDAY AFTERNOON THRU SATURDAY. WAVES
WILL BUILD IN RESPONSE TO THIS WIND SURGE, FORECASTED TO INCREASE
TO 4-7 FT BY LATE IN THE DAY FRIDAY. THE WINDS AND WAVES ALONG THE
COAST SHOULD GRADUALLY SUBSIDE LATE SATURDAY INTO SUNDAY. SUBJECT
TO CHANGE SEVERAL DAYS OUT, BUT IN-HOUSE GUIDANCE IS SUGGESTING A
MODERATE RIP CURRENT RISK FRIDAY AND MODERATE TO POSSIBLY NEAR
HIGH FOR SATURDAY. THE RISK SHOULD SUBSIDE A BIT BY 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`S LABOR DAY WEEKEND
AND THERE IS PLENTY OF SUNSHINE IN THE FORECAST.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...ROBERTSON
NEAR TERM...KLEIN
SHORT TERM...KLEIN
LONG TERM...ROBERTSON
AVIATION...KLEIN/ROBERTSON
MARINE...KLEIN/ROBERTSON
RIP CURRENTS...KLEIN


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