Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 021943
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
343 PM EDT WED SEP 2 2015

.SYNOPSIS...
A WEAK SURFACE TROUGH WILL PUSH SOUTH OF THE AREA THROUGH THURSDAY,
AHEAD OF A BACKDOOR COLD FRONT THAT WILL PUSH ACROSS THE AREA
THURSDAY NIGHT INTO FRIDAY. HIGH PRESSURE WILL BUILD ACROSS THE
REGION FROM THE NORTH SATURDAY AND REMAIN ACROSS THE AREA THROUGH
EARLY NEXT WEEK. A COLD FRONT WILL BEGIN TO APPROACH THE AREA FROM
THE WEST ON TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
HIGH PRESSURE WILL REMAIN OVER THE GULF COAST AND MIDWEST STATES
THRU TONIGHT WHILE A WEAK LOW PRESSURE TROUGH BECOMES STATIONARY
OVER THE MID-ATLANTIC REGION. TRIMMED BACK ON POPS FOR THE REST OF
THE AFTERNOON BUT AN ISOLATED POP-UP SHOWER OR STORM IS POSSIBLE
IN THE LOWER DELMARVA.

UNDER A FAVORABLE RADIATIONAL COOLING SETUP THIS EVENING, EXPECT
ANOTHER ROUND OF FOG TO DEVELOP OVERNIGHT INTO EARLY THURSDAY
MORNING. SIMILAR TO THIS MORNING, FOG WILL LIKELY BE MOST WIDESPREAD
AND DENSE FROM THE DELAWARE VALLEY TO THE COAST SINCE THE ATMOSPHERE
WILL BE PRIMED WITH HIGHER DEWPOINTS WHERE TODAY`S SEA-BREEZE FRONT
MAKES IT THRU. WILL HIGHLIGHT THE POTENTIAL FOR ANOTHER DENSE FOG
EVENT IN THE HWO. THERE IS UNCERTAINTY IN THE EXTENT OF THE DENSE
FOG TONIGHT AS THE MID-LEVEL SUBSIDENCE INVERSION THAT IS PARTIALLY
RESPONSIBLE FOR TRAPPING MOISTURE NEAR THE SURFACE WILL BE WEAKER
TONIGHT THAN IT WAS LAST NIGHT.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
THE UPPER RIDGE WILL REMAIN ANCHORED OVER THE SOUTHERN PLAINS ON
THURSDAY. A COUPLE OF THE SHORTWAVE TROUGHS TRACKING AROUND THE
PERIPHERY OF THE RIDGE WILL MOVE SOUTHEASTWARD INTO THE GREAT LAKES
AND NORTHEAST STATES. AT THE SURFACE, A PRESSURE TROUGH ASSOCIATED
WITH A SUBTLE BACKDOOR COLD FRONT WILL SHARPEN OVER SOUTHERN NEW
ENGLAND AND THE NORTHERN MID ATLANTIC. THE FRONT WILL BE SLOW TO
PROGRESS SOUTHWARD THRU OUR AREA WITH WEAK NORTHERLY STEERING FLOW
UNDER 10 KT IN THE BOUNDARY LAYER.

FORECAST SOUNDINGS INDICATE A WEAKENING OF THE CAP OVER THE NEXT 24
HOURS WITH MODEST CAA OCCURRING NEAR 700 MB. THERMODYNAMIC PROFILES
WILL BE MORE SUPPORTIVE OF CONVECTION THURSDAY THAN TODAY AS A
RESULT. HOWEVER, EXPECT ANY COVERAGE OF SHOWERS AND STORMS TO BE
PREDOMINATELY ISOLATED OWING TO A LACK OF ORGANIZED LIFT (EXCEPT FOR
LOW-LEVEL CONVERGENCE NEAR THE BACKDOOR FRONT AND ALSO ALONG THE SEA-
BREEZE BOUNDARY).

FORECAST MAX TEMPS FOR THURSDAY VERY SIMILAR TO TODAY AND
YESTERDAY`S...80S IN THE HIGHLANDS AND ALONG THE COAST, MID 90S IN
THE URBAN AREA, AND LOW 90S ELSEWHERE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
A CHANCE FOR UNSETTLED WEATHER FOR THE END OF THE WORK WEEK,
FOLLOWED BY A QUIET WEEKEND AND BEGINNING OF NEXT WEEK.

THE BACKDOOR COLD FRONT PUSHES INTO THE AREA THURSDAY NIGHT, THEN
SLOWLY SLIDES THROUGH THE AREA DURING THE DAY FRIDAY. SHOWER
ACTIVITY MAY DIMINISH SOME OVERNIGHT THURSDAY, BUT WE EXPECT
SHOWERS AND THUNDERSTORMS TO REDEVELOP DURING THE DAY FRIDAY,
ESPECIALLY FOR THE SOUTHERN HALF OF THE AREA AS THE FRONT SLOWLY
SAGS SOUTHWARD ACROSS THE AREA. PRECIPITATION AMOUNTS ARE FORECAST
TO BE FAIRLY LIGHT, GENERALLY 0.25 INCHES OR LESS. HOWEVER, THERE
COULD BE SOME HEAVIER RAINFALL AMOUNTS AS PW VALUES INCREASE TO
1.5-1.75 INCHES, ESPECIALLY WHERE THUNDERSTORMS OCCUR.

ONCE THE FRONT PUSHES SOUTH OF THE AREA FRIDAY NIGHT, HIGH PRESSURE
WILL BUILD BACK ACROSS THE EAST COAST FROM THE NORTH FROM SATURDAY
THROUGH TUESDAY, WHICH WILL PROVIDE DRY WEATHER ACROSS THE AREA. A
COLD FRONT WILL BEGIN TO APPROACH THE AREA LATE TUESDAY, AND THERE
IS A SLIGHT CHANCE A FEW SHOWERS MAY AFFECT THE NORTHWESTERN PORTION
OF THE AREA.

TEMPERATURES COOL OFF SLIGHTLY FRIDAY INTO SATURDAY, FOLLOWED BY A
WARMING TREND SUNDAY INTO TUESDAY.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...THE FOLLOWING
DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY
AND SURROUNDING AREAS.

VFR THRU THIS EVENING. AT 1930Z, A SEA-BREEZE FRONT WAS MOVING THRU
THE NJ PINE BARRENS AND NEAR MIV. THIS SEA BREEZE WILL CONTINUE TO
PROGRESS INLAND ALL THE WAY INTO THE I-95 TERMINALS BY AROUND 00Z.
WINDS WILL SHIFT FROM OUT OF THE W-NW TO THE S-SE BUT WILL BE LIGHT
(UNDER 10 KT).

THE MAIN FOCUS FOR THIS TAF PERIOD IS THE POTENTIAL FOR ANOTHER
ROUND OF FOG OVERNIGHT AND EARLY THURSDAY MORNING. WENT WITH A
PERSISTENCE FORECAST FOR TONIGHT, WHICH YIELDS A MUCH MORE
PESSISMISTIC FORECAST IN TERMS OF VISIBILITIES THAN ALL AVAILABLE
NWP AND STAT GUIDANCE HAD INDICATED THUS FAR. CONFIDENCE IN FOG IS
HIGHEST CLOSER TO THE COAST, SO WENT WITH LIFR AT MIV AND FOG EARLY
THURSDAY MORNING.

CIGS AND LOW CLOUDS LIFTS BY 14-15Z THURSDAY. VFR FOR MOST OF THE
DAY. ISOLATED SHOWERS AND STORMS FORECAST TO DEVELOPS DURING THE
AFTERNOON. FOCUS OF THIS POTENTIAL CONVECTION IS IN THE HIGHLANDS
(CLOSEST TO RDG AND ABE) AHEAD OF A COLD FRONT. ANTICIPATED COVERAGE
IS TOO LOW TO INCLUDE IN THE TAFS THIS FAR OUT.

OUTLOOK...

THURSDAY NIGHT-FRIDAY...MAINLY VFR. SCATTERED SHOWERS OR
THUNDERSTORMS POSSIBLE, WHICH MAY LOWER CIGS AND/OR VSBYS,
ESPECIALLY FRIDAY. GUSTY EAST-NORTHEAST WINDS 15-20 KNOTS FRIDAY
AFTERNOON.

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

.MARINE...
WINDS AND SEAS BELOW SCA LEVELS TONIGHT AND THURSDAY. WINDS COULD BE
AS STRONG AS 15 KT THRU THIS EVE AND AGAIN THURSDAY AFTERNOON
ONCE THE SEA-BREEZE FRONT MOVES INLAND.

OUTLOOK...

THURSDAY NIGHT...SUB-ADVISORY CONDITIONS EXPECTED AS A BACKDOOR COLD
FRONT MOVES ACROSS THE WATERS.

FRIDAY-SATURDAY NIGHT...SEAS BEGIN TO BUILD TO SMALL CRAFT ADVISORY
LEVELS WITH THE EASTERLY FETCH BEHIND THE BACKDOOR COLD FRONT DURING
THE DAY FRIDAY AND CONTINUE INTO SATURDAY. WINDS MAY APPROACH OR
EXCEED SMALL CRAFT ADVISORY LEVELS BEHIND THE BACKDOOR COLD FRONT
FRIDAY-FRIDAY NIGHT.

SUNDAY-MONDAY NIGHT...SEAS EXPECTED TO SUBSIDE BACK BELOW SMALL
CRAFT ADVISORY CONDITIONS.

&&

.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



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