Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 290103
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
903 PM EDT SUN SEP 28 2014

.SYNOPSIS...
HIGH PRESSURE WILL BE IN PLACE NEAR WEST VIRGINA THROUGH MONDAY AND MOVE
OFFSHORE BY TUESDAY WITH A LOW PRESSURE OFF THE MID-ATLANTIC
COASTLINE. ON TUESDAY A COLD FRONTAL BOUNDARY WILL MOVE SOUTHEAST
FROM THE GREAT LAKES AND BE LOCATED OFF THE MID-ATLANTIC COASTLINE
BY WEDNESDAY WITH CONTINUED LOW PRESSURE WELL OFFSHORE. ANOTHER STRONGER COLD
FRONTAL BOUNDARY WITH AN ASSOCIATED LOW PRESSURE SYSTEM ACROSS THE
GREAT LAKES WILL MOVE FROM WEST TO EAST ACROSS MOST OF THE CENTRAL
AND EASTERN UNITED STATES FRIDAY AND SATURDAY. HIGH PRESSURE WILL
BUILD IN BEHIND THE FRONT BY SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
HIGH PRESSURE CENTERED WELL OFF THE MID-ATLANTIC COAST WILL MAINTAIN
A SOUTHERLY FLOW OVER THE REGION THROUGH THE OVERNIGHT HOURS.
DEWPOINT TEMPERATURES WILL BE JUST A LITTLE HIGHER BECAUSE OF THIS
FLOW, SO PATCHY FOG COULD POP UP IN A FEW MORE PLACES COMPARED TO
PREVIOUS NIGHTS, BUT DENSE FOG IS NOT EXPECTED. LOW TEMPERATURES
WILL RANGE FROM THE LOW 50S IN THE NORTH TO THE LOW 60S SOUTH, WHICH
IS WELL ABOVE AVERAGE FOR LATE SEPTEMBER.

NO SIGNIFICANT CHANGES TO THE CURRENT PKG AS QUIET WX PATN
CONTINUES. MADE A FEW MINOR ADJUSTMENTS TO CLOUD COVER AND TEMPS
WHERE NEEDED.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
HIGH CLOUDS WILL BE MORE NOTICEABLE ON MONDAY AS MOISTURE FROM A
SYSTEM OVER THE SOUTHEAST U.S. STREAMS NORTH. THE GFS INDICATES SOME
SHOWER ACTIVITY OVER THE SOUTHERN PORTIONS OF OUR CWA DURING THE
AFTERNOON HOURS, BUT THE ECMWF IS LESS AGGRESSIVE SO NO PRECIPITATION
WAS INCLUDED IN THE GRIDS ATTM. THE INCREASED CLOUDINESS SHOULD
KEEP TEMPERATURES A FEW DEGREES COOLER THAN SUNDAY. HIGHS ARE
EXPECTED TO RANGE FROM THE LOW 70S NORTH TO THE MID TO UPPER 70S
SOUTH.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
MONDAY NIGHT THROUGH WEDNESDAY NIGHT: MODELS HAVE COME INTO A
GREATER AGREEMENT OF ANY COASTAL LOW PRESSURE STAYING WELL OFFSHORE.
HOWEVER, THIS WILL KEEP WINDS FROM THE NORTHEAST AND EAST OVER THIS
PERIOD AND KEEP TEMPERATURES DOWN AS WELL. STAYED RELATIVITY CLOSE
TO MAV/MET GUIDANCE ON TEMPERATURES IN THIS PERIOD WITH LITTLE MODEL
SPREAD PRESENT. THE ECMWF ENSEMBLE SPREAD AND MANY GFS ENSEMBLE
MEMBERS ACTUALLY IMPLY THE LOW PRESSURE SYSTEM WILL STAY EVEN
FURTHER OFFSHORE THAN FEATURED IN THE OPERATIONAL RUNS. INCREASED
CONFIDENCE ANY COASTAL LOW WILL STAY OFFSHORE, PERHAPS A NORTHWARD
EXTENSION OF A INVERTED TROUGH INTO OUR REGION BUT LEFT FORECAST DRY
MONDAY NIGHT ATTM. DID INCLUDE SOME PATCHY FOG AROUND SUNRISE
TUESDAY. MAIN FEATURE IN THIS PERIOD WILL BE A WEAK FRONTAL BOUNDARY
LIKELY TO PASS THROUGH TUESDAY NIGHT INTO WEDNESDAY. BEHIND THE
FRONT THERE LOOKS TO BE A NICE SPIKE IN VORTICITY ASSOCIATED WITH
A UPPER LEVEL LOW. HOWEVER THE SURFACE BOUNDARY WILL BE DECAYING
AND MOISTURE WILL BE LIMITED. BUFKIT SOUNDINGS ONLY INDICATE PW
VALUES UNDER 1 INCH AND VERY DRY MID LEVELS WITH RH ONLY AROUND
50%. SO EVEN WITH GOOD MID-LEVEL SUPPORT IT`S GOING TO BE HARD TO
GENERATE ANYTHING MORE THAN SOME SCATTERED SHOWERS WITH LIGHT QPF,
CHANCE POPS AS WELL. WITH STEEPING LAPSE RATES AND SOME VERY
LIMITED CAPE (UNDER A FEW HUNDRED J/KG) WEDNESDAY AFTERNOON, A FEW
ADDITIONAL SPOTTY LIGHT SHOWERS ARE POSSIBLE WITH THE DEVELOPMENT
OF SCATTERED CUMULUS. AREAS NW OF PHL WOULD BE FAVORED FOR THIS
WITH HIGHER TERRAIN.

THURSDAY THROUGH SATURDAY: BOTH THE GFS AND ECMWF SHOW A COASTAL LOW
WELL OFFSHORE THAT STALLS OR MOVES SLOW EAST TO START. THIS WILL
KEEP THE REGION IN A EASTERLY FLOW THAT TURNS MORE SOUTHEAST BY
FRIDAY AHEAD OF THE NEXT FRONTAL BOUNDARY. THIS FRONTAL BOUNDARY
IS LIKELY TO MOVE THROUGH SOMETIME IN THE FRIDAY NIGHT AND
SATURDAY TIME PERIOD. THIS FRONT WILL HAVE QUITE A BIT MORE
MOISTURE TRANSPORTED NORTH FROM THE GULF OF MEXICO COMPARED TO THE
FRONT IN THE TUESDAY NIGHT TIMEFRAME. PW VALUES LOOK TO BE HIGHER
AROUND 1.5 INCHES, SO SOME HEAVY SHOWERS CAN NOT BE RULED OUT.
INSTABILITY LOOKS ALMOST NON-EXISTENT, PERHAPS 100 J/KG AS SHOWN
ON THE 00Z ECMWF. NO ADDITION OF THUNDER TO THE GRIDS FRIDAY NIGHT
AND SATURDAY. A FACTOR WHICH WOULD LIMIT PRECIPITATION IS THAT THE
AREA OF MAXIMUM MID-LEVEL ENERGY AND DYNAMICS WILL BE PASSING WELL
TO OUR NORTHEAST. GIVEN THE POTENTIAL FOR LIMITED MID AND UPPER
LEVEL SUPPORT, LEFT POPS IN THE CHANCE RANGE.


SATURDAY NIGHT AND SUNDAY: NORTHWEST FLOW WITH DRIER AIR AND HIGH
PRESSURE BUILDING IN FOR SATURDAY NIGHT AND SUNDAY. STUCK CLOSE TO
WPC GUIDANCE ON TEMPERATURES EXCEPT FOR SUNDAY GIVEN THE MODELED
925 MB TEMPERATURES WHICH SUGGEST HIGH TEMPERATURES MAY BE SEVERAL
DEGREES COOLER. FOR SUNDAY MORNING 12Z GFS LOW TEMPERATURES
COUPLED WITH LIGHT WINDS INDICATE THE POTENTIAL FOR PATCHY FROST.
HOWEVER THINK THIS IS TO COOL ATTM.

&&

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

.TONIGHT AND MONDAY...VFR CONDITIONS EXPECTED. SOME PATCHY FOG IS
POSSIBLE LATE SUNDAY NIGHT / EARLY MONDAY MORNING, BUT WITH NO MAJOR
IMPACT ON AVIATION EXPECTED. SOME HIGH CLOUDS...ALL WITH CIGS AOA
10000 FEET, ALONG WITH LIGHT SOUTHWESTERLY WINDS 10 KT OR LESS.

OUTLOOK...
MONDAY NIGHT AND TUESDAY: SOME LOW MVFR CLOUDS AND PATCHY FOG
AROUND SUNRISE TUESDAY OTHERWISE VFR.


TUESDAY NIGHT AND WEDNESDAY: SOME MVFR CEILINGS POSSIBLE TUESDAY
AND WEDNESDAY WITH SOME SCATTERED SHOWERS, OTHERWISE VFR. E/NE WINDS
AROUND 10 KNOTS.

WEDNESDAY NIGHT THROUGH FRIDAY: VFR. NE WINDS 5 TO 10 KNOTS BECOMING
SOUTHEAST.

&&

.MARINE...
PLEASANT CONDITIONS EXPECTED ON THE WATERS AND MONDAY AS HIGH
PRESSURE CONTINUES TO MOVE EAST. SRLY OR SERLY WINDS
TONIGHT...BECOMING SWRLY ON MONDAY...ALL GENERALLY 10 KNOTS OR LESS.
WAVES 2 TO 3 FT ON THE OCEAN AND 1 TO 2 FT ACROSS DEL BAY.

OUTLOOK...
MONDAY NIGHT AND TUESDAY: WINDS AND SEAS INCREASE WITH DEVELOPING EASTERLY
FLOW BUT REMAIN BELOW SCA CRITERIA.

TUESDAY NIGHT THROUGH FRIDAY: WITH LOW PRESSURE OFF THE COAST A
AVERAGE EASTERLY FLOW IN LIKELY TO REMAIN IN PLACE. THIS WILL KEEP
SEAS ABOVE FIVE FEET WITH A BRIEF LULL POSSIBLE FRIDAY AFTERNOON, WINDS WILL
LIKELY ALSO REMAIN ABOVE SCA CRITERIA THROUGH MOST OF THE PERIOD.

&&

.TIDES/COASTAL FLOODING...
A 1 FOOT OR GREATER ONSHORE FLOW POSITIVE DEPARTURE SURGE
IS POSSIBLE FOR MID AND LATE WEEK. RIGHT NOW THE BEST CHANCE FOR MINOR
COASTAL FLOODING WOULD BE WITH THE WEDNESDAY AFTERNOON TIDAL CYCLE
BUT DEPARTURES LOOK ABOUT 1/2 FOOT SHORT NOW ON WEDNESDAY.

&&

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

&&

$$
SYNOPSIS...GAINES
NEAR TERM...NIERENBERG/MIKETTA
SHORT TERM...MIKETTA
LONG TERM...GAINES
AVIATION...GAINES/MIKETTA
MARINE...GAINES/MIKETTA
TIDES/COASTAL FLOODING...





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