Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 241658
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1258 PM EDT THU JUL 24 2014

.SYNOPSIS...
A COLD FRONTAL BOUNDARY WILL CONTINUE MOVING OFFSHORE
TODAY. HIGH PRESSURE WILL BUILD ACROSS THE OHIO VALLEY TONIGHT AND
ON FRIDAY. THE HIGH PRESSURE SYSTEM WILL MOVE EAST OF THE REGION ON
SATURDAY AND BE FOLLOWED BY THE PASSAGE OF A WARM FRONT FROM THE
SOUTH BY SATURDAY NIGHT AND BE LOCATED TO OUR NORTH ON SUNDAY.
ANOTHER COLD FRONTAL BOUNDARY THEN WILL SWEEP FROM WEST TO EAST
ACROSS THE REGION ON MONDAY. A HIGH PRESSURE SYSTEM WILL BUILD IN
BEHIND THE COLD FRONT FOR THE MIDDLE HALF OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE CDFNT HAS MOVED SOUTH OF OUR CWA.

NEXT ESTF UPDATE WE WILL SHAVE BACK MENTION OF POPS FURTHER. THE
HRRR AND COSPA TREND HAS BEEN FOR LESS AND LESS. THIS IS LIKELY
DUE TO THE CIRRUS SHIELD SLOWING OUR TEMP ASCENT TO THE CONVECTIVE
TEMP AS MOST OF OUR TEMP ERRORS HAVE BEEN ON THE HIGH SIDE. SOME
OF THE SHWRS IN NOVA HAVE BEEN UNDERDONE BY THE MESOSCALE MODELS,
SO WILL KEEP A BUFFER LOW CHC INTO CENTRAL DELMARVA AND PARTS OF
SERN NJ. BASED ON THE SLOWER TEMP ASCENT AND WHERE THEY ARE
CURRENTLY OCCURRING, WE NOW HAVE THE MENTION OF THUNDER ONLY IN
OUR FAR SRN CWA AND ADJACENT COASTAL WATERS. FAIRLY UNIFORM MAX
TEMPS AWAY FROM THE HIGHER TERRAIN EXPECTED THIS AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
HIGH PRES WILL BUILD EWD AND INTO THE AREA TONIGHT.  ANY PRECIP WILL
END EARLY AND THE SKY WILL CLEAR.  OVERALL, A QUIET NIGHT IS IN
STORE.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
FRIDAY AND FRIDAY NIGHT: HIGH PRESSURE GLIDES EAST FROM THE OHIO
VALLEY INTO OUR REGION. VARIABLE WINDS, PLENTY OF SUNSHINE AND NOT
THAT HOT SINCE THIS AIRMASS WILL BE COMING FROM CANADA! LITTLE
SPREAD IN THE MODELS ON MOST IF NOT ALL WEATHER ELEMENTS. TRICKIEST
PART OF THIS PERIOD IS HOW MUCH RADIATIONAL COOLING CAN OCCUR IN
RURAL AREAS BEFORE THE FLOW TURNS MORE SOUTHERLY BY SATURDAY.
OPTED TO GO A TOUCH COOLER THAN MEX/MAV/MET IN A FEW SPOTS WITH
LOWS FRIDAY NIGHT.

SATURDAY AND SATURDAY NIGHT: A WARM FRONT APPROACHES THE REGION FROM
THE SOUTH AND WITH A DEPARTING HIGH PRESSURE THE FLOW TURNS
SOUTHERLY. MODELED MOMENTUM TRANSFER SUGGESTS SOME GUSTS CLOSE TO 20
MPH ARE POSSIBLE IN THE AFTERNOON, WENT HIGHER THAN A STANDARD
125% FOR WIND GUSTS. MID-LEVEL AND SURFACE TEMPERATURES LOOK TO
RESPOND IN KIND AFTER THE WARM FRONTAL PASSAGE, 925 MB TEMPS NEAR 20-22C
SHOULD YIELD SURFACE TEMPERATURES JUST UNDER 90 FOR PHL AND IN THE
80`S ELSEWHERE ACROSS THE REGION. HUMIDITY IS ON THE RISE BUT THIS
WILL BE LIKE MORE TYPICAL JULY HEAT WITH HEAT INDEX VALUES WELL
UNDER ADVISORY LEVELS. THE WARM FRONT MAY PROVIDE ENOUGH LIFT FOR
SOME SCATTERED SHOWERS AND THUNDERSTORMS FOCUSED ACROSS THE
NORTHERN PART OF THE REGION. THE 21Z SREF AND THE LAST TWO ECMWF
RUNS HAVE THESE PINED DOWN WELL. INCREASING CIN COUPLED WITH 700
MB TEMPS NEAR 10C COULD ALLOW FOR THE FORMATION OF A WEAK CAP
ACROSS THE SOUTHERN PART OF THE REGION, BEING FURTHER AWAY LOWER
CHANCE POPS WERE WARRANTED WHEN COMPARED TO LOCATIONS FURTHER
NORTH.

SUNDAY AND SUNDAY NIGHT: CONTINUED WEST-SOUTHWEST FLOW IN THE WARM
SECTOR. THE LAST FEW GFS RUNS HAVE BEEN MORE AGGRESSIVE WITH
CONVECTION BY THE AFTERNOON AND EVENING HOURS. A COMMON THEME THIS
SUMMER. THINK THE GFS IS TO AGGRESSIVE WITH THIS. HOWEVER, STORM
CHANCES SHOULD INCREASE AS THE MAIN LOW PRESSURE SYSTEM AND COLD
FRONT APPROACH THE REGION. GOOD AGREEMENT AMONG THE GFS ENSEMBLES,
ECMWF ENSEMBLE MEAN AND THE OPERATIONAL MODELS THAT THE HIGHEST
CHANCE WILL BE SUNDAY NIGHT. MAINTAINED LOW END LIKELY POPS ACROSS THE
NORTH AND HIGH END CHANCE ACROSS THE SOUTH. FOR QPF STAYED CLOSE TO
THE SREF AND ECMWF SIMILAR TO SATURDAY. THOUGH DID RAISE IT SLIGHTLY
TO ACCOUNT FOR THE MORE AGGRESSIVE GFS. TEMPERATURES MAY BE RAIN
COOLED SUNDAY BUT DID NOT GO IN THAT DIRECTION ATTM. FAIR SHOT AT 90
FOR PHL WITH SLIGHTLY WARMER MODELED MID-LEVEL TEMPERATURES THAN
SATURDAY.

MONDAY AND MONDAY NIGHT: THE COLD FRONT MOVES THROUGH LIKELY MONDAY
AFTERNOON. HOWEVER THIS SHOULD BE TO LITTLE TO LATE IN TERMS OF
ANOTHER ROUND OF SHOWERS AND STORMS. THE MAIN CAPE AXIS IS LIKELY TO
OFFSHORE AT THIS TIME AND LITTLE IS LEFT FOR A TRIGGER BESIDES THE
ACTUAL FRONTAL BOUNDARY. HOWEVER MAINTAINED LOW CHANCE POPS SINCE THE
FRONT WILL STILL BE IN THE REGION. CLEARED CONDITIONS OUT MONDAY
NIGHT WITH A RETURN TO WESTERLY FLOW. ANOTHER GUSTY DAY AS ONCE
MODELED MOMENTUM TRANSFER SHOWS POTENTIAL FOR SOME GUSTS NEAR 20
MPH.


TUESDAY AND WEDNESDAY: ANOTHER CANADIAN AIRMASS COMES DOWN INTO THE
REGION AS THE SAME GENERAL PATTERN FROM THE WINTERTIME CONTINUES
WITH FEW BREAKS. COOL NORTHWESTERLY FLOW WILL BE IN PLACE AS MOST
LOCATIONS STRUGGLE TO 80 FOR A HIGH. EVEN WITH THIS ABNORMALLY COOL
AIRMASS THERE IS GOOD AGREEMENT AMONG THE MEX, WPC AND MODELED TWO
METER TEMPERATURES. TRENDED SLIGHTLY COOLER THAN WPC GIVEN THE
LATEST 00Z ECMWF WHICH IS ON THE COOLEST END OF THE MODEL GUIDANCE.
LAPSE RATES MAY STEEPEN UP TUESDAY AFTERNOON FOR THE FORMATION OF
SOME CUMULUS AND SPOTTY SHOWERS/THUNDER ON THE BACKSIDE OF THE TROUGH
ACROSS THE NORTH WITH THE AID OF ELEVATION. OTHERWISE BOTH DAYS
LOOK MOSTLY SUNNY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

18Z TAFS HAVE VFR CONDITIONS FCST THRUT. LOWEST CONFIDENCE AT KACY.

FOR THIS AFTERNOON, NW TERMINALS/AIRPORTS MIGHT DEVELOP A VFR CU
BASED CIG. ELSEWHERE MULTIPLE LAYER VFR CLOUDS PREDICTED TO PERSIST.
NOT CONFIDENT AT KACY IF CIG WILL REMAIN COMPLETELY VFR,
ESPECIALLY AFTER SEA BREEZE FRONT PASSES. THERE WILL BE SOME MVFR
CIGS AT AIRPORTS CLOSER TO THE COAST.

WINDS WILL BE NORTH TO NORTHWEST CLOSE TO 10 KNOTS. AT KACY A SEA
BREEZE FRONT IS PREDICTED TO PASS LATE THIS AFTERNOON. THE SEA
BREEZE FRONT SHOULD GET TO ABOUT CENTRAL NEW JERSEY (ROUGHLY THE
WESTERN BORDERS OF ALL OF THE COASTAL COUNTIES AND EAST OF 70 IN
BURLINGTON) BEFORE STALLING.

TONIGHT VFR CONDITIONS ARE PREDICTED TO PERSIST WITH CLOUDINESS
SLOWLY DISSIPATING. THE TAF CLOUD FORECAST IS WEIGHED MORE TOWARD
EVENING CONDITIONS. WINDS SHOULD BE LIGHTER FROM THE NORTHWEST. WE
ARE NOT ANTICIPATING ANY FOG AT THE TERMINALS.

ON FRIDAY A VFR DAY WITH NO CIG PREDICTED AND JUST FEW/SCATTERED CU
BASED CLOUDS. A SEA BREEZE FRONT SHOULD FORM AGAIN AND WITH
HIGHER TEMPS FASTER, MAKE ITS WAY TO KACY BY 18Z. NOT CONFIDENT
ABOUT IT REACHING TO KPHL LATE THAT AFTERNOON, SO NOT INCLUDED IN
THIS TAF.

OUTLOOK...
FRIDAY NIGHT...VFR

SATURDAY THROUGH MONDAY...BRIEF MVFR AND IFR RESTRICTIONS IN
SCATTERED THUNDERSTORMS. HIGHEST CHANCE FOR RESTRICTIONS IS ON
SUNDAY AFTERNOON AND EVENING FOR RDG, ABE, TTN, AND POINTS NORTH.

&&

.MARINE...
WITH HIGH PRES BUILDING INTO THE REGION, NO MARINE HEADLINES ARE
ANTICIPATED THRU THE NR AND SHORT TERM PDS.

OUTLOOK...
FRIDAY THROUGH SATURDAY NIGHT: SEAS AND WINDS EXPECTED TO STAY UNDER
SCA CRITERIA. A FEW WIND GUSTS AROUND 20 KNOTS POSSIBLE SATURDAY
AFTERNOON.

SUNDAY AND MONDAY: SEAS INCREASE TO FOUR FEET ON SUNDAY AND PERHAPS
FIVE FEET BY MONDAY MORNING BEFORE FALLING BELOW FIVE FEET MONDAY
NIGHT. A FEW WIND GUSTS AROUND 20 KNOTS POSSIBLE SUNDAY AND MONDAY
AFTERNOONS.

&&

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

&&

$$
SYNOPSIS...GAINES
NEAR TERM...GIGI
SHORT TERM...NIERENBERG
LONG TERM...GAINES
AVIATION...GAINES/GIGI/KEARNS
MARINE...GAINES/NIERENBERG





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