Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 271930
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
330 PM EDT MON APR 27 2015

.SYNOPSIS...
A LARGE AND COMPLEX LOW PRESSURE SYSTEM OVER THE WESTERN NORTH
ATLANTIC WILL CONTINUE TO MOVE SLOWLY OUT TO SEA. MEANWHILE, HIGH
PRESSURE WILL TRY TO BUILD INTO OUR REGION GRADUALLY FROM THE
NORTHWEST AND WEST THROUGH WEDNESDAY. ANOTHER AREA OF LOW PRESSURE
IS FORECAST TO PASS OFF THE NORTH CAROLINA COAST ON THURSDAY
AFTERNOON. THE LOW IS EXPECTED TO STRENGTHEN AS IT MOVES OUT TO
SEA ON THURSDAY NIGHT AND FRIDAY. HIGH PRESSURE IS ANTICIPATED TO
BUILD INTO OUR REGION FROM THE WEST FOR THE COMING WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
MID AND UPPER LEVEL TROUGH WILL BEGIN TO SLIDE AWAY FROM THE
REGION, AS A RESULT, WHAT LITTLE CHANCE OF RAIN SHOWERS THERE IS
SHOULD BE NEGLIGIBLE BY LATE THIS EVENING. DESPITE THE RELATIVELY
DRY BOUNDARY LAYER, WITH DEW POINT DEPRESSIONS OF 20 DEGREES OR
MORE THIS AFTERNOON, MID LEVELS REMAIN MOIST ENOUGH TO SUPPORT
EXTENSIVE CLOUDS UNTIL SUBSIDENCE BEGINS IN THE WAKE OF THE MID
LEVEL TROUGH.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
BY TOMORROW, THE LOW OVER THE NORTHWEST ATLANTIC WILL BE NEARLY
VERTICALLY STACKED. OUR REGION WILL STAY UNDER THE INFLUENCE OF
NORTHWESTERLY AND NORTHERLY FLOW AS THIS LOW SLOWLY SLIDES EAST
AWAY FROM THE REGION. THICKNESSES WILL INCREASE SLIGHTLY, THUS
EXPECT A MODEST WARMING TREND WITH HIGHS GENERALLY IN THE UPPER
50S TO UPPER 60S.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
WE SHOULD REMAIN UNDER THE OUTER INFLUENCE OF A MID LEVEL LOW OFF
NOVA SCOTIA ON TUESDAY NIGHT. A WEAK MID LEVEL RIDGE IS FORECAST
TO APPROACH FROM THE WEST AND NORTHWEST AND IT IS FORECAST TO BE
OVERHEAD ON WEDNESDAY AND WEDNESDAY NIGHT. DRY WEATHER IS EXPECTED
FROM TUESDAY NIGHT THROUGH WEDNESDAY NIGHT ALTHOUGH THERE SHOULD
BE AN INCREASE IN HIGH LEVEL CLOUDS DURING THE PERIOD.

A LONG WAVE MID LEVEL TROUGH IS ANTICIPATED TO BE OVER THE
EASTERN STATES FOR THURSDAY INTO FRIDAY. A CLOSED LOW IS FORECAST
TO DROP FROM THE GREAT LAKES TO THE MIDDLE ATLANTIC STATES FROM
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT BEFORE MOVING EASTWARD AND
OFF THE COAST ON FRIDAY.

SURFACE LOW PRESSURE IS EXPECTED TO MOVE FROM GEORGIA AND SOUTH
CAROLINA ON WEDNESDAY TO THE WATERS OFF CAPE HATTERAS ON THURSDAY
AFTERNOON. THERE REMAINS SOME DISAGREEMENT AMONG THE MODEL
GUIDANCE REGARDING THE STRENGTH AND TRACK OF THE LOW AS IT MOVES
OUT TO SEA ON THURSDAY NIGHT AND FRIDAY. WHILE A FAIR AMOUNT OF
CLOUD COVER SEEMS LIKELY, THE NORTHWESTERN EXTENT OF THE MAIN
PRECIPITATION SHIELD WITH THE SYSTEM REMAINS A LOW CONFIDENCE
FORECAST. ALSO, AN AREA OF CONVECTIVE PRECIPITATION IS EXPECTED TO
DEVELOP OVER THE OHIO RIVER VALLEY ON WEDNESDAY NIGHT INTO
THURSDAY IN RESPONSE TO THE MID LEVEL LOW. SOME REMNANT OF THAT
ACTIVITY MAY DRIFT TOWARD OUR REGION, AS WELL.

THE MODEL GUIDANCE SEEMS TO BE SUGGESTING A DRY WEDGE POKING DOWN
INTO OUR REGION FROM THE NORTHEAST FOR THURSDAY INTO THURSDAY
NIGHT DUE TO THE CIRCULATION AROUND THE LOW. ALSO, SUBSIDENCE
AROUND THE SYSTEM MAY CONTRIBUTE TO THE DEVELOPMENT OF AN AREA OF
LESSENING PRECIPITATION AROUND ITS OUTER EDGE. AS A RESULT, WE
WILL KEEP OUR PRECIPITATION PROBABILITIES MAINLY IN THE CHANCE
RANGE.

THE WIND FORECAST ASSOCIATED WITH THE SYSTEM REMAINS A BIT
UNCERTAIN, AS WELL. WHILE THE BACKING FROM AN EAST TO A NORTH WIND
FROM THURSDAY INTO FRIDAY APPEARS LIKELY, THE SPEED FORECAST IS
DEPENDENT UPON THE EVENTUAL TRACK OF THE SYSTEM. WE HAVE GONE WITH
A MIDDLE OF THE ROAD SOLUTION FOR THE TIME BEING.

THE LONG WAVE TROUGH IS FORECAST TO MOVE OUT OVER THE WESTERN
NORTH ATLANTIC FOR THE WEEKEND. A MID LEVEL SHORT WAVE MAY DROP
DOWN FROM THE NORTHWEST AROUND SUNDAY. THE FEATURE IS ANTICIPATED
TO HAVE LIMITED MOISTURE ASSOCIATED WITH IT. A RIDGE FROM THE WEST
IS FORECAST TO BUILD OVER THE EASTERN STATES ON MONDAY.

DAYTIME TEMPERATURES SHOULD BE ABOVE NORMAL ON WEDNESDAY, THEN
THEY ARE FORECAST TO FALL BELOW NORMAL FOR THURSDAY AND FRIDAY DUE
TO THE CLOUD COVER, EAST TO NORTH WIND AND POSSIBLE RAIN.
TEMPERATURES ARE EXPECTED TO RETURN ABOVE NORMAL OVER THE WEEKEND.

&&

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

VFR CONDITIONS SHOULD CONTINUE THROUGH THE TAF PERIOD, WITH
MOSTLY MID LEVEL CLOUDS BETWEEN 4000 AND 8000 FT AGL. THERE IS A
SMALL CHANCE OF LOW LEVEL CLOUDS (AROUND 2000 FT AGL) DEVELOPING
PRIMARILY WEST OF THE FALL LINE, INCLUDING KRDG AND KABE, BETWEEN
09 AND 15Z. HOWEVER, GIVEN HOW DRY THE AIR MASS IS IN THE BOUNDARY
LAYER, THINK THIS IS VERY UNLIKELY. WINDS WILL BE NORTHWESTERLY
AND GUSTY THROUGH SUNSET, THEN DECREASE SOME THROUGH 12Z. AFTER
12Z, WINDS WILL SHIFT TO MORE NORTHERLY AND INCREASE ONCE AGAIN.

OUTLOOK...

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...MAINLY VFR.

THURSDAY AND THURSDAY NIGHT...MAINLY VFR WITH A CHANCE OF RAIN.
CONDITIONS MAY DROP INTO THE MVFR RANGE AT TIMES. AN EAST TO
NORTHEAST WIND AROUND 10 TO 15 KNOTS IS EXPECTED ALONG WITH ITS
POTENTIAL IMPACT ON OPERATIONS AT KPHL.

FRIDAY...MAINLY VFR WITH A CHANCE OF SHOWERS.

FRIDAY NIGHT AND SATURDAY...MAINLY VFR.

&&

.MARINE...
SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED TO DEVELOP LATE THIS
EVENING, WITH WIND GUSTS AT OR JUST ABOVE 25KT. WIND GUSTS SHOULD
BEGIN TO DIMINISH BY MID TUESDAY MORNING. ONCE WIND SPEEDS
DECREASE, SUB SCA CONDITIONS ARE EXPECTED FOR THE REMAINDER OF THE
DAY. SEAS WILL LIKELY REMAIN BELOW 5 FT THROUGH THE ENTIRE PERIOD.

OUTLOOK...

TUESDAY NIGHT THROUGH THURSDAY MORNING...NO MARINE HEADLINES ARE
ANTICIPATED.

THURSDAY AFTERNOON THROUGH FRIDAY...A SMALL CRAFT ADVISORY WILL
LIKELY BE NEEDED FOR WIND GUSTS OF 25 TO 30 KNOTS AND FOR WAVES ON
OUR OCEAN WATERS IN EXCESS OF 5 FEET. THE WIND DIRECTION IS
ANTICIPATED TO BACK GRADUALLY FROM THE EAST TO THE NORTH. THERE IS
THE POTENTIAL FOR GALE FORCE GUSTS IF LOW PRESSURE OVER THE OCEAN
TRACKS CLOSER TO THE COAST THAN CURRENTLY EXPECTED.

FRIDAY NIGHT AND SATURDAY...WIND SPEEDS ARE FORECAST TO REMAIN
BELOW THE SMALL CRAFT ADVISORY CRITERION. HOWEVER, WAVE HEIGHTS ON
OUR OCEAN WATERS MAY REMAIN AROUND OR ABOVE 5 FEET.

&&

.FIRE WEATHER...
NORTH NORTHWESTERLY WINDS GUSTING ABOVE 20 MPH WILL BE POSSIBLE
ACROSS THE REGION ON TUESDAY. RELATIVE HUMIDITY VALUES AROUND 30
PERCENT ARE POSSIBLE PRIMARILY OVER NJ, SOUTHEASTERN PA (SOUTHEAST
OF THE POCONOS), AND EXTREME NORTHERN DELMARVA. SINCE CONDITIONS
WILL BE MARGINAL AT WORST, WILL WAIT FOR AT LEAST ONE MORE FULL
SUITE OF MODEL RUNS BEFORE MAKING A DECISION IF TO ISSUE AN SPS OR
RFW.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO NOON EDT
     TUESDAY FOR ANZ430-431-450>455.

&&

$$

SYNOPSIS...IOVINO
NEAR TERM...JOHNSON
SHORT TERM...JOHNSON
LONG TERM...IOVINO
AVIATION...IOVINO/JOHNSON
MARINE...IOVINO/JOHNSON
FIRE WEATHER...JOHNSON


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