Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 150135
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
935 PM EDT SUN SEP 14 2014

.SYNOPSIS...
HIGH PRESSURE ACROSS THE REGION TONIGHT WILL MOVE OFFSHORE BY
LATER MONDAY. A COLD FRONT IS THEN EXPECTED TO CROSS OUR REGION LATE
MONDAY NIGHT AND EARLY TUESDAY. HIGH PRESSURE WILL BUILD ACROSS THE
REGION TUESDAY AND WEDNESDAY, THEN A WEAK COLD FRONT MAY SETTLE
THROUGH OUR AREA LATER WEDNESDAY OR EARLY THURSDAY. HIGH PRESSURE
THEN BUILDS IN FOR THURSDAY AND FRIDAY BEFORE SHIFTING OFFSHORE
SATURDAY, WITH ANOTHER COLD FRONT POSSIBLY APPROACHING LATER SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
WE CONTINUE WITH THE MOSTLY CLEAR SKIES TONIGHT THOUGH SOME OF THE
STRATOCU IS BEING A BIT MORE STUBBORN ACROSS THE COAST. THIS AREA
SHOULD PUSH OFFSHORE OR DISSIPATE OVER THE NEXT COUPLE OF HOURS.
STILL NOT QUITE SURE ON THE EXTENT OF MORE STRATOCU ADVECTING INTO
THE REGION FROM THE SOUTHWEST LATE TONIGHT. GUIDANCE SHOWS DECENT
LOW-LEVEL HUMIDITY VALUES, BUT THE MORE ROBUST MODELS INITIALIZED
TOO MOIST SO WE KEEP WITH THE MOSTLY CLEAR.

WITH LIGHT NORTHWEST OR CALM WIND AND RATHER COOL TEMPS...7 TO 12
DEGREES BELOW NORMAL. IDEAL RADIATIONAL COOLING CONDITIONS. LOWS
IN THE 40 TO 45 DEGREE RANGE EXCEPT LOWER 50S URBAN CENTERS AND 45
TO 50 DELMARVA. EXPECT SOME FOG IN THE RIVER VALLEYS ACROSS OUR
NORTH.

THE 12Z/14 50 50 BLENDED NAM/GFS GUIDANCE WAS ALREADY UPDATED INTO
THE FCST GRIDS AND WORDING.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
A SUNNY MORNING WITH SOME INCREASING CLOUDS DURING THE LATE AFTERNOON
FROM CIRRUS THRU AC AND SC LAYERS. NEAR OR SLIGHTLY BELOW NORMAL TEMPS
FOR MID SEPTEMBER. BLENDED 12Z/14 GFS/NAM MOS GUIDANCE WITH LIGHT
WINDS TRENDING SW IN THE AFTN EXCEPT SEA BREEZES COAST.

EXCEPTION COULD BE MD E SHORE AND SE PA WHERE A DECK OF CLOUDS
FROM WVA MAY ARRIVE DURING THE MORNING. NEEDS REEVALUATION OVERNIGHT.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH
FROM THE MIDWEST TO THE NORTHEAST THROUGH ABOUT THURSDAY. SOME SHORT
WAVES EMBEDDED IN THE FLOW WILL AMPLIFY THE TROUGH SOME EASTWARD A
FEW TIMES, ONE MOST NOTABLY SLIDING BY MONDAY NIGHT AND TUESDAY
MORNING. AN UPPER-LEVEL RIDGE IS THEN FORECAST TO MIGRATE ACROSS THE
MIDDLE OF THE NATION THURSDAY INTO FRIDAY, ALLOWING THE TROUGH TO
LIFT OUT SOME OF THE NORTHEAST. A POTENTIAL RIDGE COULD THEN BUILD
ACROSS PORTIONS OF THE EAST AND ALSO THE SOUTHERN STATES FRIDAY AND
SATURDAY. AN ASSOCIATED SURFACE HIGH WILL BUILD ACROSS OUR AREA BUT
THEN SHIFT OFFSHORE SATURDAY. AS THE HIGH GIVES WAY AND A TROUGH
AMPLIFIES ACROSS THE MIDWEST TO GREAT LAKES, THE NEXT COLD FRONT IS
SCHEDULED TO APPROACH OUR AREA LATER SUNDAY. A MODEL BLEND WAS USED
FOR MONDAY NIGHT THROUGH WEDNESDAY, THEN UTILIZED THE 12Z WPC
GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING
ADDITIONAL COLLABORATION WITH OUR SURROUNDING OFFICES.

FOR MONDAY NIGHT AND TUESDAY...A SHORT WAVE DIVING ACROSS THE GREAT
LAKES MONDAY NIGHT WILL HELP DEVELOP A WEAK SURFACE LOW NEAR THE MID
ATLANTIC. AS SOME WAA INCREASES AHEAD OF IT, AN INCREASE IN THE
CLOUDS WILL OCCUR. THE ARRIVAL OF LARGE SCALE LIFT COMBINED WITH
SOME DEEPER MOISTURE SHOULD ALLOW FOR A RIBBON OF SHOWERS TO DEVELOP
LATER MONDAY NIGHT. WHILE THERE IS STILL SOME QUESTION ON HOW
ORGANIZED THE SHOWERS WILL BE AS THE SYSTEM IS GENERALLY MOVING
QUICKLY, ENOUGH MOISTURE AND LIFT SHOULD GENERATE A TIME OF FAIRLY
WIDESPREAD SHOWERS. THIS APPEARS TO BE MORE FOCUSED ACROSS THE
CENTRAL AND NORTHERN ZONES, WHICH ARE CLOSER TO THE SHORT WAVE
PASSAGE. THEREFORE, POPS WERE MAINTAINED AS INCREASING FROM WEST TO
EAST WITH LIKELY POPS INDICATED MAINLY LATE /HIGHEST ACROSS THE
CENTRAL AND NORTHERN AREAS/.

AN AMPLIFYING UPPER-LEVEL TROUGH WILL SWING ACROSS THE NORTHEAST AND
MID ATLANTIC REGION TUESDAY, TAKING WEAK LOW PRESSURE WITH IT. THIS
FEATURE LOOKS TO BE PROGRESSIVE, THEREFORE ANY SHOWERS WILL BE
ENDING TUESDAY MORNING WITH IMPROVING CONDITIONS SETTING IN DURING
THE AFTERNOON AND AT NIGHT. THE ARRIVAL OF DRIER AND COOLER AIR
ALONG WITH INCREASING SUBSIDENCE SHOULD ALLOW FOR CLEARING TO TAKE
PLACE ESPECIALLY AT NIGHT. THERE COULD BE SOME STRATOCUMULUS WITHIN
THE WEAK CAA REGIME FOR A TIME ESPECIALLY TOWARD THE NORTHWEST
ZONES, AND IT MAY BE A BIT BREEZY AT TIMES DURING THE DAY WITH SOME
DEEPER MIXING.

FOR WEDNESDAY THROUGH FRIDAY...WHILE AN UPPER-LEVEL TROUGH IS
FORECAST TO BE IN PLACE WEDNESDAY AND THURSDAY, SURFACE HIGH
PRESSURE WILL ARRIVE FROM THE WEST. THIS WILL DELIVER ANOTHER ROUND
OF DRIER AIR ALONG WITH A COOL AIRMASS. A WEAK COLD FRONT HOWEVER
MAY SETTLE SOUTHEASTWARD ACROSS OUR AREA LATE WEDNESDAY INTO
THURSDAY, WITH A NEW AIRMASS AND ASSOCIATED SURFACE HIGH PRESSURE
BUILDING BACK IN FOR FRIDAY. THE FRONT CONTINUES TO LOOK RATHER WEAK
WITH LIMITED MOISTURE, THEREFORE KEPT THE FORECAST DRY. MOST OF
THE WEATHER ELEMENTS WERE FAIRLY CLOSE TO THE 12Z WPC GUIDANCE.

FOR SATURDAY AND SUNDAY...A BUILDING RIDGE TO OUR SOUTH AND EAST
SHOULD SUPPORT AN EXPANSIVE SURFACE HIGH THAT WILL BE SHIFTING TO
OUR EAST. THE PLACEMENT OF THIS HIGH WILL BE CRUCIAL IN DETERMINING
OUR SENSIBLE WEATHER, AS AN ONSHORE FLOW MAY HANG ON FOR AWHILE AND
CAUSE CLOUDINESS DUE TO THE OCEAN INFLUENCE. OVERALL, LESS CERTAINTY
WITH THE DETAILS THIS FAR OUT HOWEVER THE SURFACE HIGH LOOKS TO
DOMINATE OVERALL. AN AMPLIFYING TROUGH ACROSS THE MIDWEST AND GREAT
LAKES IS SCHEDULED TO DRIVE A COLD FRONT TOWARD OUR AREA LATER
SUNDAY, WITH THE FLOW TURNING MORE SOUTHERLY ALLOWING FOR WARMER AIR
TO ADVECT INTO OUR CWA. OVERALL, WE STAYED CLOSE TO THE 12Z WPC
GUIDANCE.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THROUGH TONIGHT...VFR. LIGHT NORTHWEST OR CALM WIND. SMALL CHANCE
PATCHY FOG NEAR SUNRISE IN THE SHELTERED RIVER VALLEYS. ALSO A
SMALL CHC OF A 3000 FT DECK OF SC EDGING INTO THE KRDG AREA AROUND
10-12Z BUT LOW PROBABILITY ATTM.

MONDAY...VFR DURING THE MORNING WITH MULTI LAYERS AOA 4000 FT
ARRIVING LATE IN THE DAY (SC, AC, CI). LIGHT WIND BECOMING SW
DURING THE AFTN EXCEPT SE ALONG THE COASTS.

OUTLOOK...
MONDAY NIGHT AND TUESDAY...MAINLY VFR. SOME SHOWERS SHOULD MOVE
THROUGH LATE MONDAY NIGHT AND EARLY TUESDAY MORNING WITH BRIEF
SUB-VFR CONDITIONS. SOUTH-SOUTHWEST WINDS 5-10 KNOTS BECOMING
NORTHWESTERLY MONDAY NIGHT INTO TUESDAY, THEN INCREASING TO 10-15
KNOTS TUESDAY.

WEDNESDAY THROUGH FRIDAY...VFR OVERALL AS HIGH PRESSURE DOMINATES
OUR WEATHER.

&&

.MARINE...
QUIET THROUGH MONDAY WITH NO HEADLINES. ATLC SEAS GENERALLY AOB 3
FT. DE BAY WAVES MOSTLY 1 FT OR LESS. WINDS VARIABLE ONSHORE LATE
THIS AFTERNOON LESS THAN 10 KT BECOMING LIGHT NORTHWEST TONIGHT
AND MONDAY MORNING THEN ONSHORE SELY MON AFTN.

OUTLOOK...
MONDAY NIGHT AND TUESDAY...A QUICK MOVING SYSTEM CROSSES OUR AREA
LATER MONDAY NIGHT AND EARLY TUESDAY MORNING ALLOWING FOR A WIND
SHIFT TO OCCUR. DESPITE THE WINDS SHIFTING TO THE NORTHWEST OR NORTH
TUESDAY AND INCREASING SOME, IT APPEARS THAT THE WINDS AND SEAS
OVERALL REMAIN BELOW ADVISORY CRITERIA.

WEDNESDAY THROUGH FRIDAY...A NORTH TO NORTHEAST FLOW COULD BE A BIT
GUSTY AT TIMES ESPECIALLY FRIDAY AND THIS WILL BUILD THE SEAS SOME.
THE WINDS MUCH OF THE TIME THOUGH SHOULD BE BELOW ADVISORY CRITERIA.
HOWEVER, THE SEAS AS OF NOW MAY REACH 5 FEET ESPECIALLY ACROSS OUR
CENTRAL AND SOUTHERN COASTAL WATERS DUE TO THE NORTHEASTERLY FLOW.
OUR CONFIDENCE LOWERS THROUGH THIS PERIOD GIVEN LESS CERTAINTY WITH
THE PRESSURE GRADIENT.

&&

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

&&

$$
SYNOPSIS...GORSE
NEAR TERM...DRAG/HEAVENER
SHORT TERM...DRAG
LONG TERM...GORSE
AVIATION...DRAG/GORSE
MARINE...DRAG/GORSE






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