Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 031533
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1133 AM EDT THU SEP 3 2015

.SYNOPSIS...
A BACKDOOR COLD FRONT WILL SLIDE SOUTHWESTWARD ACROSS THE AREA
LATER TONIGHT AND EARLY FRIDAY MORNING. HIGH PRESSURE WILL THEN
BUILD INTO OUR REGION FROM THE NORTH SATURDAY AND SUNDAY BEFORE
SHIFTING OFFSHORE EARLY NEXT WEEK. A WEAKENING COLD FRONT IS THEN
FORECAST TO GRADUALLY ARRIVE LATER WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A PRESSURE TROUGH WAS LOCATED NEAR CAPE CODE, EXTENDING
SOUTHEASTWARD TO JUST OFF THE NJ AND DELMARVA COAST. A LEE SURFACE
TROUGH IS FORECAST TO DEVELOP INLAND THIS AFTERNOON NEAR I-95 WHERE
NORTHERLY WINDS TO THE WEST OF THE TROUGH AXIS CONVERGE WITH
ONSHORE FLOW ASSOCIATED WITH THE INLAND MOVING SEA-BREEZE.

SKIES WILL REMAIN SUNNY THRU THE REMAINDER OF THE MORNING BEFORE CU
FIELD DEVELOPS DURING THE PEAK HEATING HOURS THIS AFTERNOON. IT
SHOULD REMAIN DRY THRU AT LEAST EARLY AFTERNOON. MADE SOME MINOR
TWEAKS TO THE POP/WX GRIDS FOR TODAY BY CONFINING ISOLATED
SHOWERS AND STORMS TO FAR SOUTHERN AND FAR NORTHERN ZONES. ACROSS
THE LOWER DELMARVA, ENHANCED LOW-LEVEL CONVERGENCE ALONG THE
TROUGH AXIS IS FORECAST IN ADDITION TO LOCALLY HIGHER INSTABILITY,
WHICH MAY YIELD AN ISOLATED STORM OR TWO DURING THE MID
AFTERNOON. ISOLATED SHOWERS AND STORMS WERE ALSO HIGHLIGHTED IN
NORTHEAST PA AND NORTHWEST NJ. THE FOCUS FOR CONVECTION UP THERE
WILL BE TERRAIN CIRCULATIONS AS WELL AS A BACKDOOR COLD FRONT
THAT WILL BE DROPPING SOUTHWARD FROM UPSTATE NY. THIS ACTIVITY IS
FAVORED LATE IN THE DAY DUE TO A DELAYED ARRIVAL OF THIS FRONT.

THE LATE SEASON HEAT WILL CONTINUE ANOTHER DAY WITH HIGHS IN THE
LOWER 90S ACROSS MOST OF THE AREA (EXCEPT COOLER NEAR THE COAST
AND IN THE HIGHER ELEVATIONS OF NORTHEAST PA/NORTHWEST NJ). THE
HEAT INDEX MAY TOP OFF IN THE 94-96F RANGE FOR THE HOT SPOTS
WITHIN THE URBAN I-95 CORRIDOR.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
THE SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM WILL CONTINUE INTO
EARLY TONIGHT WITH SOME LINGERING INSTABILITY AND WITH THE SURFACE
TROUGH. A COLD FRONT APPROACHING FROM THE NORTH IS ANTICIPATED TO
DROP THROUGH OUR REGION LATE TONIGHT. THE FRONT IS NOT EXPECTED TO
ENHANCE OUR CHANCE FOR PRECIPITATION AS CONDITIONS ARE FORECAST TO
STABILIZE GRADUALLY DURING THE NIGHT.

MINIMUM TEMPERATURES SHOULD BE MAINLY IN THE UPPER 60S AND LOWER
70S.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
THE SYNOPTIC SETUP IS COMPRISED OF A RIDGE SLIDING EASTWARD OVER
OUR AREA FRIDAY AND SATURDAY. THIS RIDGE IS THEN FORECAST TO
FLATTEN OUT EARLY NEXT WEEK AS A SHORT WAVE TROUGH SLIDES ACROSS
THE NORTHERN TIER OF STATES. OVERALL, THIS PATTERN SHOULD FAVOR
WARMTH AND DRYNESS ALTHOUGH A BRIEF 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 FRIDAY INTO SUNDAY, WITH A 00Z WPC GUIDANCE/CONTINUITY BLEND
THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE AFTER ADDITIONAL
COLLABORATION WITH OUR NEIGHBORING OFFICES.

FOR FRIDAY...A BACKDOOR COLD FRONT IS FORECAST TO BE SHIFTING
WEST AND SOUTH OF OUR AREA. ANY CONVECTION SHOULD THEREFORE BE
SHIFTING SOUTHWESTWARD WITH TIME AS SURFACE HIGH PRESSURE STARTS
TO BUILD ACROSS NEW ENGLAND. THIS WILL RESULT IN THE LOW-LEVEL
FLOW BEING FROM THE EAST OR NORTHEAST, AND WITH MORE OF AN OCEAN
INFLUENCE SOME COOLING OF THE AIR MASS IS ANTICIPATED. THE DRIER
AIR MAY WIN OUT AND THEREFORE DESPITE THE ONSHORE FLOW WE SHOULD
HAVE SOME DECREASE IN THE CLOUDS ESPECIALLY ACROSS THE NORTHERN
AREAS. HOWEVER IF THE TRANSITION IS DELAYED OR IS NOT CLEAN LIKE
SOME GUIDANCE SUGGESTS, THEN A PERIOD OF LOW CLOUDS MAY BE
POSSIBLE BEFORE THE DRIER AIR PRESSES FARTHER SOUTH. IF THIS WERE
TO OCCUR, THE SOUTHERN AND WESTERN PORTIONS OF THE AREA SHOULD
HAVE THE HIGHEST CHC. SINCE THE PROSPECTS OF SHOWERS AND
THUNDERSTORMS IS ON THE LOWER SIDE, WE KEPT THE POPS AT OR BELOW
LOW CHC, WITH THE BETTER CHC LOOKING LIKE THE WESTERN ZONES TO
PORTIONS OF THE DELMARVA. THERE DOES APPEAR TO BE A WINDOW WHERE
BREEZY CONDITIONS DEVELOP ESPECIALLY CLOSER TO THE COAST. THE IDEA
OF MORE CLOUDINESS/LOW CLOUD DEVELOPMENT WAS INCORPORATED INTO THE
SKY GRIDS IN THE AFTERNOON AND AT NIGHT, MAINLY FOR THE SOUTHERN
PORTIONS OF THE CWA.

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.
THERE COULD BE SOME RESIDUAL CLOUDINESS MAINLY ACROSS THE FAR
SOUTHERN ZONES TO START SATURDAY DEPENDING ON THE DRY AIR PUSH,
OTHERWISE NO SIGNIFICANT WEATHER IS ANTICIPATED ATTM. WE START TO
LOSE THE COOLER ONSHORE INFLUENCE, AND THEREFORE THE DAYTIME
TEMPERATURES ARE ANTICIPATED TO REBOUND SUNDAY AFTERNOON FOR MUCH
OF THE AREA.

FOR MONDAY THROUGH WEDNESDAY...A SHORT WAVE TROUGH MOVING NEAR
THE U.S.-CANADIAN BORDER SHOULD FLATTEN THE RIDGE. 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 LOOKS TO TRACK WELL TO OUR NORTH TUESDAY, THEREFORE THE
CHCS FOR CONVECTION SHOULD MOSTLY REMAIN TO OUR WEST. SOME
GUIDANCE SUGGESTS THE INITIAL SHORT WAVE TROUGH LIFTING WELL INTO
CANADA AS A SECONDARY SHORT WAVE TROUGH CROSSES THE MIDWEST
WEDNESDAY. IT IS A WEAK COLD FRONT WITH THIS FEATURE THAT MAY END
UP MOVING THROUGH OUR AREA LATER WEDNESDAY. THERE IS MORE
UNCERTAINTY WITH THE TIMING OF THESE FEATURES THIS FAR OUT. GIVEN
THE LINGERING RIDGE TO THE SOUTH, A SLOWER EASTWARD PROGRESSION OF
THE SURFACE FRONT MAY RESULT. AS THE FLOW IS MORE SOUTHERLY, A
RATHER WARM AIR MASS LOOKS TO BE IN PLACE WITH SOME INCREASE IN
THE DEW POINTS.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

VFR THRU THE AFTN AND INTO THE EVE. SOME VISIBILITY RESTRICTIONS
ARE AGAIN POSSIBLE LATE TONIGHT WITH FOG.

ISOLATED SHOWERS AND THUNDERSTORMS MAY DEVELOP IN VICINITY OF
ABE AND RDG TERMINALS AFTER 18Z TODAY BEFORE THE ACTIVITY DECAYS
THIS EVENING WITH THE LOSS OF DAYTIME HEATING. HOWEVER, THE
CHANCE OF ANY OF OUR TAF SITES BEING AFFECTED IS LOW AND WE WILL
NOT MENTION THE POTENTIAL IN THE TAF PRODUCTS.

THE WIND IS FORECAST TO FAVOR THE NORTH AND NORTHWEST FOR TODAY
AT LESS THAN 10 KNOTS. HOWEVER, A SURFACE TROUGH IS EXPECTED TO
MOVE INLAND FROM THE OCEAN AND IT SHOULD AFFECT KACY THIS
AFTERNOON BRINGING THE WIND AROUND TO EAST AND SOUTHEAST THERE.

A LIGHT AND VARIABLE WIND THIS EVENING SHOULD BECOME NORTHEAST
LATE TONIGHT AS A COLD FRONT DROPS THROUGH OUR REGION FROM THE
NORTH. WIND SPEEDS ARE FORECAST TO REMAIN LESS THAN 10 KNOTS.

OUTLOOK...
FRIDAY...VFR OVERALL. SOME SHOWERS OR THUNDERSTORMS ARE POSSIBLE,
ESPECIALLY FROM NEAR THE KPHL AREA ON WEST AND SOUTH. THERE IS A
CHANCE FOR A PERIOD OF LOW CLOUD /MVFR/ DEVELOPMENT IN THE
AFTERNOON AND EVENING ESPECIALLY FROM ABOUT KRDG TO KPHL TO KACY
ON SOUTHWARD, HOWEVER THIS IS OF LOWER CONFIDENCE AT THIS TIME.
EAST- NORTHEAST WINDS INCREASE TO 10-15 KNOTS, WITH SOME GUSTINESS
IN THE AFTERNOON AND EVENING MAINLY CLOSER TO THE COAST.

SATURDAY THROUGH MONDAY...MOSTLY VFR. EAST-NORTHEAST WINDS MAINLY
10- 15 KNOTS SATURDAY, DIMINISHING AND BECOMING SOUTHEASTERLY
SUNDAY BEFORE TURNING SOUTH-SOUTHWEST ON MONDAY.

&&

.MARINE...
A SURFACE TROUGH IS FORECAST TO BE OVER OUR COASTAL WATERS THIS
MORNING BEFORE IT DRIFTS INLAND THIS AFTERNOON. A COLD FRONT IS
EXPECTED TO ARRIVE FROM THE NORTH LATE TONIGHT.

THE WIND IS ANTICIPATED TO BE VARIABLE THIS MORNING BEFORE
SETTLING INTO THE SOUTHEAST FOR THIS AFTERNOON AND EARLY TONIGHT.
THE WIND IS EXPECTED TO BECOME EAST TO NORTHEAST LATE TONIGHT.
SPEEDS SHOULD REMAIN AT 10 KNOTS OR LESS.

WAVE HEIGHTS ON OUR OCEAN WATERS ARE FORECAST TO BE 1 TO 2 FEET
FOR THIS AFTERNOON AND TONIGHT WITH WAVES ON DELAWARE BAY BEING 2
FT OR LESS.

OUTLOOK...
FRIDAY AND SATURDAY...AS A BACKDOOR FRONT MOVES THROUGH, THE
WINDS WILL TURN FROM THE EAST AND NORTHEAST AND INCREASE. IT
APPEARS THAT GUSTS TO AROUND 25 KNOTS OCCUR FROM NORTH TO SOUTH ON
THE COASTAL WATERS LATER FRIDAY AFTERNOON THROUGH SATURDAY MORNING
BEFORE A DECREASE BEGINS. AS A RESULT, A SMALL CRAFT ADVISORY
LOOKS TO BE NEEDED. THE ONSHORE FLOW WILL ALSO BUILD THE SEAS TO
AROUND 5 FEET STARTING LATE FRIDAY ON THE COASTAL ATLANTIC WATERS.

SUNDAY AND MONDAY...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 BELOW
ADVISORY CRITERIA, HOWEVER THIS WILL DEPEND ON HOW HIGH THEY GET
ON THE ATLANTIC COASTAL WATERS FRIDAY AND SATURDAY.

&&

.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...GORSE
NEAR TERM...KLEIN
SHORT TERM...IOVINO
LONG TERM...GORSE
AVIATION...GORSE/IOVINO/KLEIN
MARINE...GORSE/IOVINO/KLEIN
RIP CURRENTS...KLEIN


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