Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 280820
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
420 AM EDT SUN SEP 28 2014

.SYNOPSIS...
HIGH PRESSURE OVER THE AREA WEAKENS TONIGHT AND MONDAY. A BACKDOOR
COLD FRONT IS EXPECTED TO MOVE SOUTH ACROSS THE AREA TUESDAY. FOR
MIDWEEK, HIGH PRESSURE IS FORECAST TO STRENGTHEN ACROSS EASTERN
CANADA, WHILE WEAK LOW PRESSURE EAST OF THE CAROLINAS MOVES SLOWLY
NORTHEAST THROUGH THURSDAY. A COLD FRONT EXTENDING SOUTH ACROSS
THE GREAT LAKES AND OHIO VALLEY FRIDAY SHOULD CROSS OUR REGION
SATURDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE WILL REMAIN ACROSS THE AREA TODAY. AFTER SOME PATCHY
MORNING FOG LIFTS...SKIES WILL BE MOSTLY SUNNY FOR THE BALANCE OF
THE DAY. SOME HIGH CLOUDS MAY CROSS THE AREA...BUT THIS WILL DO
LITTLE TO KEEP TEMPERATURES FROM RISING INTO THE UPPER 70S TO LOW
80S ACROSS THE REGION. THESE TEMPERATURES ARE ABOUT 10 DEGREES ABOVE
NORMAL FOR LATE SEPTEMBER. WINDS WILL BE LIGHT TODAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
THE HIGH WILL BEGIN TO WEAKEN ACROSS THE AREA...BUT STILL FAIR
WEATHER IS EXPECTED. AGAIN...MORE PATCHY OVERNIGHT FOG WILL DEVELOP
AFTER MIDNIGHT. LOW TEMPERATURES WILL BE SOMEWHAT MILD FOR LATE
SEPTEMBER...BEING IN THE UPPER 50S TO LOW 60S IN MANY AREAS. WINDS
WILL BE LIGHT.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
500 MB: A COUPLE OF SHORT WAVES MOVE THROUGH THE MID AND NORTH
ATLANTIC STATES MONDAY THROUGH WEDNESDAY AND BECOME BETTER ORGANIZED
SOUTHEAST OF NEW ENGLAND THURSDAY AND FRIDAY. THEREAFTER A LARGE
AMPLITUDE TROUGH IN CENTRAL NORTH AMERICA NEXT WEEKEND EDGES EAST.

TEMPERATURES: SEPTEMBER WILL END UP AT LEAST A DEGREE ABOVE NORMAL
AS CALENDAR DAY AVERAGE TEMPERATURES ARE FORECAST TO BE ABOUT 10
DEGREES ABOVE NORMAL MONDAY AND 5 TO 8 DEGREES ABOVE NORMAL TUESDAY
THROUGH FRIDAY BEFORE COOLING CLOSER TO NORMAL DURING NEXT WEEKEND.

FORECAST BASIS: UNLESS OTHERWISE NOTED THE LONG TERM PERIOD OF THIS
FORECAST IS GENERALLY BASED ON A 50 50 BLEND OF THE 00Z/28 NAM/GFS
MOS FOR THE PERIOD MONDAY-TUESDAY...THE 00Z/28 GFS MOS TUESDAY
NIGHT-WEDNESDAY...THEN THEREAFTER (WEDNESDAY NIGHT ONWARD) THE
0643Z/28 WPC GRIDDED GUIDANCE WHICH AT TIMES IS BLENDED 50 50
WITH THE 00Z/28 MEXMOS. ALL THIS IS EVENTUALLY CHECKED AGAINST THE
00Z/28 ECMWF TO SEE IF WE`RE IN THE BALLPARK WITH ECMWF CYCLICALLY
PERSISTENT 18Z 2 METER TEMPERATURES. PRECIPITATION PROBABILITY
GUIDANCE IS CHECKED AGAINST THE 21Z/27 SREF 3HRLY POPS FOR .01
THROUGH 00Z SATURDAY AND THEREAFTER THE 00Z/28 GEFS 6HR POPS FOR
0.05.

THE DAILIES...

MONDAY-WEDNESDAY...VARIABLE CLOUDINESS (IN PART INSTABILITY DRIVEN)
WITH PROBABLY A BAND OR 2 OF SHOWERS AS SHORT WAVES PASS THROUGH
THE REGION. THE MOSTLY LIKELY TIME FOR SHOWER OCCURRENCE IS TUESDAY
AFTERNOON-WEDNESDAY. THUNDER IS POSSIBLE (NOT GRIDDED INTO THE
FCST YET) WITH SUBZERO SWI AND TT NEAR 52...MAINLY E PA.

MODELS ARE WAFFLING AND SO CONFIDENCE ON DETAILS ARE STILL WELL
BELOW AVERAGE. ON THIS 00Z/28 CYCLE...ECMWF/GFS/NAM ARE ALL MORE
DEFINED...POTENT.

THERE IS STILL ROOM IN THE MODELS FOR STRENGTHENING THIS SYSTEM
CLOSER TO THE COAST OR DEVELOPING A SEPARATE SFC LOW (NO LINK TO
THE CAROLINAS SFC LOW) OVER NORTHERN PA...BENEATH THE DEVELOPING
CIRCULATION ALOFT AND THEN REDEVELOPING THIS N PA SFC WAVE JUST S
OF LONG ISLAND ON WEDNESDAY.

SO THE FORECAST HAS FOCUSED POPS LATE TUE-WED. THESE POPS ARE
STILL CONSERVATIVE DUE TO UNCERTAINTY BUT HAVE TO BELIEVE THAT
THERE WILL BE A BAND OF MEASURABLE RAIN BETWEEN .01 AND .75
INCHES MOVING EWD ACROSS THE I78 REGION NORTHWARD LATE TUE INTO
WEDNESDAY. THIS IS OVER AN AREA THAT DEFINITELY HAS SEEN A
SHORTFALL OF RFALL THIS YEAR. AGAIN UNCERTAINTY AS OF THIS
WRITING.

THE IMPACT OF TUESDAYS BACKDOOR COLD FRONT APPEARS TO BE DELAYED
12-18 HOURS UNTIL TUE NIGHT-WED. THEREFORE...OUR 330 AM FORECAST
HAS WARMER TEMPERATURES FOR TUESDAY THAN OUR COOLER PRIOR FORECAST.

THURSDAY-FRIDAY...WEAKENING NORTHEAST FLOW AND PROBABLY DRY AS THE
RIDGE ALOFT BUILDS INTO THE AREA FROM THE WEST BEHIND THE DEVELOPING
NW ATLC CYCLONIC CIRCULATION.

NEXT WEEKEND...A COLD FRONTAL PASSAGE IS EXPECTED WITH PROBABLY A
BAND OF SHOWERS FRIDAY NIGHT OR SATURDAY THEN PROBABLY A DRIER
SUNDAY.

TIDES: A 1 FOOT OR GREATER ONSHORE FLOW POSITIVE DEPARTURE SURGE
WILL BE DEVELOPING FOR MID AND LATE WEEK. RIGHT NOW NO THREAT FOR
MINOR CF. IF THE LOW PRESSURE SYSTEM DEVELOPS CLOSER TO THE COAST
WE COULD HAVE A LITTLE MORE CONCERN.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

ANOTHER FINE FLYING WEATHER DAY EXPECTED ACROSS THE REGION. THERE
WILL BE PATCHY FOG ACROSS THE AREA WITH LOCALLY LOW VSBYS EARLY THIS
MORNING...BUT AFTER THAT MOSTLY CLR SKIES AND LIGHT WINDS. SOME CI
CLOUDS WILL MOVE ACROSS THE AREA THIS MORNING. WINDS WILL BE 5 TO 8
KTS THIS AFTERNOON...MOSTLY FROM TH W OR SW. VFR TONIGHT WITH AGAIN
PATCHY FOG OVERNIGHT.

OUTLOOK...
MONDAY THROUGH TUESDAY...MAINLY VFR CIGS AOA 10000 FT MONDAY AND
AOA 4000 FT TUESDAY. POSSIBLE SUB-VFR VSBYS LATE MONDAY NIGHT OR
TUESDAY IN A FEW SHOWERS OR STRATUS/FOG. LIGHT SOUTHWEST WIND MONDAY
BECOME EASTERLY TUESDAY. SMALL CHC ISOLATED THUNDER E PA LATE TUE.

WEDNESDAY THROUGH THURSDAY...VFR CIGS WITH A CHANCE FOR PERIODS OF
MVFR CONDS IN SHOWERS...ESPECIALLY WEDNESDAY AND ESPECIALLY
KABE/KRDG. NE WIND GUST 15-20 KT.

&&

.MARINE...
PLEASANT CONDITIONS EXPECTED ON THE WATERS TODAY AND TONIGHT. HIGH
PRESSURE WILL MOVE EAST TONIGHT. WINDS WILL BE MOSTLY UNDER 10 KNOTS
WITH DIRECTIONS VARIABLE THIS MORNING...THEN SRLY OR SERLY THIS
AFTERNOON AND TONIGHT. WAVES 2 TO 3 FT ON THE OCEAN AND 1 TO 2 FT
ACROSS DEL BAY.

OUTLOOK...
MONDAY...NO MARINE HEADLINE WITH A LIGHT SOUTHWEST WIND SHIFTING
E LATE MONDAY NIGHT.

TUESDAY THROUGH THURSDAY...WINDS AND SEAS ARE EXPECTED TO REACH
SMALL CRAFT ADVISORY LEVELS SOMETIME DURING TUESDAY OR TUESDAY
NIGHT. SCA CONDITIONS ONCE DEVELOPED WILL LIKELY LAST THROUGH AT
LEAST THURSDAY AS LOW PRESSURE DEVELOPS SOMEWHERE OFF THE MID
ATLC COAST. THE TRACK AND ORGANIZATION OF THIS SYSTEM IS STILL
UNCERTAIN AT THIS TIME. HAZARDOUS SEAS OF 5 FT OR GREATER ON THE
ATLANTIC WATERS MAY LINGER THROUGH FRIDAY OR SATURDAY.

&&

.CLIMATE...
RERMPO YDY..EQUALED RECORD MAX.

&&

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

&&

$$
SYNOPSIS...DRAG
NEAR TERM...O`HARA
SHORT TERM...O`HARA
LONG TERM...DRAG 319
AVIATION...DRAG/O`HARA 319
MARINE...DRAG/O`HARA 319
CLIMATE...






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