Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 280814
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
414 AM EDT TUE OCT 28 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OFFSHORE TODAY. A COLD FRONT APPROACHES
THE AREA OVERNIGHT AND MOVES THROUGH WEDNESDAY. HIGH PRESSURE WILL
BRIEFLY BUILD IN FOR THURSDAY BEFORE AN AREA OF LOW PRESSURE MOVES
OUT OF THE GREAT LAKES REGION AND COMBINES WITH A DEVELOPING COASTAL
LOW OFFSHORE OF THE MID ATLANTIC. HIGH PRESSURE RETURNS FOR THE END
OF THE WEEKEND AND EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE HAS MOVED OFF THE SOUTHEAST AND MID-ATLANTIC COAST
EARLY THIS MORNING. MEANWHILE, A 998 MB SFC LOW WAS LOCATED NEAR
LAKE MICHIGAN WITH A COLD FRONT EXTENDING SOUTHWESTWARD ACROSS THE
MIDWEST AND SOUTHERN PLAINS.

THE MID-ATLANTIC REGION IS LOCATED UNDERNEATH DEEP WESTERLY FLOW
ALOFT ATOP THE RIDGE. DUE TO THE DEVELOPMENT OF A STRONG NOCTURNAL
INVERSION, THERE WASN`T MUCH EVIDENCE OF A WARM FRONT EAST OF THE
APPALACHIANS ON THE LATEST SFC ANALYSIS DESPITE THE SIGNIFICANT WAA
ALOFT. SFC TEMPS OVERNIGHT VARY CONSIDERABLY FROM LOCATION TO
LOCATION, RANGING FROM THE UPPER 30S/LOWER 40S WHERE WINDS HAVE
DECOUPLED AND RADIATIONAL COOLING WAS HIGHLY EFFECTIVE TO THE 50S
WHERE THERE WAS STILL A LIGHT SOUTHERLY WIND.

HIGH CLOUDS AROUND THE PERIPHERY OF THE RIDGE ARE STREAMING IN FROM
THE WEST EARLY THIS MORNING BUT THESE CLOUDS ARE EXPECTED TO THIN
OUT OVER THE MID-ATLANTIC REGION LATER THIS MORNING AS THE BULK OF
THE UPPER-LEVEL MOISTURE SHIFTS DOWNSTREAM INTO THE NORTHEAST.

AHEAD OF THE MIDWEST COLD FRONT, THE CORE OF THE WARM SECTOR WILL
BECOME ESTABLISHED OVER MID-ATLANTIC STATES THIS AFTERNOON. MAJORITY
OF MODEL GUIDANCE SHOWS 925 MB AND 850 MB TEMPS FOR PHL INCREASING
TO AROUND 21C AND 17C RESPECTIVELY, WHICH IS A +2 SD OCCURRENCE FOR
LATE OCTOBER. ASSUMING FULL MIXING DOWN FROM THE 925 MB WARM NOSE,
TEMPS WOULD REACH THE LOWER TO MID 80S. MAX TEMP FORECAST IS NOT
QUITE THAT WARM (SINCE FULL MIXING NOT EXPECTED OWING TO THE LOW SUN
ANGLE) BUT IS SEVERAL DEGREES ABOVE STAT GUIDANCE. FORECAST HIGHS IN
LOW 80S IN THE DELMARVA AND MID TO UPPER 70S ELSEWHERE MATCHES UP
WELL WITH UPSTREAM OBSERVATIONS YESTERDAY IN THE MIDWEST.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
LOW PRESSURE WILL CONTINUE TO LIFT NORTH OF THE GREAT LAKES TONIGHT
AND TOWARDS JAMES BAY. THE COLD FRONT WITH THIS SYSTEM IS EXPECTED
TO CROSS THE APPALACHIANS THIS EVENING AND SHOULD BE ON THE FRONT
DOOR STEP OF OUR FAR WESTERN ZONES IN EASTERN PA BY DAYBREAK. THE
TREND OF RECENT GUIDANCE WAS TO SLOW DOWN THE PROGRESSION OF THE
FRONT EVER SO SLIGHTLY. FOLLOWED THIS TREND WITH POPS OVERNIGHT,
KEEPING ANY MENTION OF SHOWERS WEST OF THE FALL LINE. POPS FOLLOW
CLOSE SUITE TO THE 21Z/03Z SREF RUNS.

WENT ABOVE MOS GUIDANCE FOR MIN TEMP AS SOUTHWESTERLY FLOW IN
PRE-FRONTAL WARM SECTOR AND INCREASING CLOUD COVER LATE SHOULD LIMIT
RADIATIONAL COOLING.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
A COLD FRONT WILL BE MOVING INTO THE AREA AT THE BEGINNING OF THE
DAY WEDNESDAY AND PROGRESS ITS WAY THROUGH THE AREA DURING THE DAY
AND INTO THE EVENING. POPS WILL INCREASE FROM WEST TO EAST THROUGH
THE DAY AS THE FRONT MOVES THROUGH. MODEL GUIDANCE IS IN PRETTY GOOD
AGREEMENT WITH THE PRECIP OCCURRING MOSTLY FROM LATE MORNING THROUGH
THE AFTERNOON HOURS. THERE IS SOME DIFFERENCES IN QPF AMOUNTS, BUT
OVERALL DOES NOT LOOK LIKE A SIGNIFICANT AMOUNT OF RAIN, GENERALLY
ONE-TENTH TO ONE-QUARTER OF AN INCH OR LESS. THE FRONT MOVES
OFFSHORE BY LATE IN THE DAY, AND THE MAIN SHORT WAVE MOVES THROUGH
OVERNIGHT. PRECIP CHANCES WILL DIMINISH FROM WEST TO EAST THROUGH
THE LATE AFTERNOON AND EVENING, AND SHOULD BE ALL OUT OF THE AREA BY
OR SHORTLY AFTER MIDNIGHT.

HIGH PRESSURE IS EXPECTED TO BRIEFLY AFFECT THE AREA THURSDAY INTO
THURSDAY NIGHT. DRY WEATHER AND NEAR NORMAL TEMPERATURES ARE
EXPECTED BEFORE A CHANGE FOR THE UPCOMING WEEKEND.

ON FRIDAY, AND AREA OF LOW PRESSURE WILL BE MOVING OUT OF THE GREAT
LAKES REGION, AND APPROACHING THE AREA, WHILE A COASTAL LOW DEVELOPS
AND STRENGTHENS TO OUR SOUTHEAST. WE DO NOT EXPECT ANY PRECIPITATION
DURING THE DAY AS THE PRECIPITATION TIED TO THE APPROACHING LOW TO
THE NORTHWEST SHOULD STILL BE TO OUR NORTHWEST. HOWEVER, AS WE GO
INTO SATURDAY NIGHT, THE LOW TO THE NORTHWEST IS EXPECTED TO BEGIN
GETTING ABSORBED BY THE COASTAL LOW. AT THE SAME TIME, THE MID/UPPER
TROUGH WILL BE DIVING SOUTHWARD INTO THE AREA AS WELL. THIS WILL
ALLOW PRECIPITATION TO FILL IN ACROSS THE AREA. THE MID/UPPER TROUGH
WILL SLOWLY SWING ACROSS THE AREA THROUGH SATURDAY, SO THERE COULD
STILL BE SHOWERS ACROSS THE AREA THROUGH THE DAY SATURDAY. THERE IS
SOME COLD AIR ASSOCIATED WITH THE MID/UPPER TROUGH SWINGING ACROSS
THE AREA WITH SUB-ZERO 925/850MB TEMPERATURES LATE FRIDAY NIGHT
THROUGH SATURDAY INTO SATURDAY NIGHT. THERE IS THE POTENTIAL FOR
SOME SNOW TO MIX WITH RAIN, OR EVEN A COMPLETE CHANCE OVER ACROSS
THE HIGHER ELEVATIONS.

WINDS WILL ALSO INCREASE SATURDAY INTO SATURDAY NIGHT AS THE
PRESSURE GRADIENT TIGHTENS SIGNIFICANTLY BETWEEN THE COASTAL LOW AND
HIGH PRESSURE TO THE WEST.

IMPROVING CONDITIONS ARE EXPECTED FOR SUNDAY INTO MONDAY AS HIGH
PRESSURE IS EXPECTED TO BUILD INTO THE REGION FROM THE WEST. THE 00Z
ECMWF IS SLOWER TO MOVE THE COASTAL LOW TO THE NORTHWEST, BUT THE
THOUGHT IS THIS MAY BE TO SLOW.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

VFR TODAY AND TONIGHT WITH MAINLY HIGH CLOUDS EXPECTED. CLOUDS WILL
INCREASE AND CIGS WILL START TO LOWER IN VC OF RDG/ABE AFTER 06Z
WEDNESDAY. LIGHT AND VARIABLE WINDS EARLY THIS MORNING. S-SW WINDS
5-10 KT THIS AFTERNOON AND TONIGHT. CONSIDERED INCLUDING LLWS FOR
THE 00Z-12Z WEDNESDAY PERIOD WITH A 40-45 KT LLVL JET BUT SHEAR
VALUES NOT QUITE REACHING THRESHOLD FOR THE TAFS.


WEDNESDAY...SCATTERED SHOWERS POSSIBLE WHICH MAY PERIODICALLY REDUCE
CIGS/VSBYS.

WEDNESDAY NIGHT-FRIDAY...MOSTLY VFR.

FRIDAY NIGHT-SATURDAY...GENERALLY VFR, WITH MVFR CONDITIONS
POSSIBLE WITH SHOWERS. SNOW SHOWERS POSSIBLE ACROSS NORTHEAST
PENNSYLVANIA AND NORTHWEST NEW JERSEY. STRONG, GUST WINDS SATURDAY
INTO SATURDAY NIGHT.

&&

.MARINE...
SWLY WINDS WILL STRENGTHEN TODAY TO 10-20 KT. THE GRADIENT TIGHTENS
A BIT MORE TONIGHT. WARM AIR ATOP THE COOLER OCEAN WATERS DO NOT
PROVIDE A PARTICULARLY FAVORABLE MIXING SETUP BUT OCCASIONAL GUSTS
TO 25 KT ARE POSSIBLE OVER THE COASTAL WATERS LATE. USING WAVEWATCH
GUIDANCE, SEAS WILL INCREASE TO 4-5 FT OVERNIGHT. A SCA WAS ISSUED
FOR THE ATLANTIC ZONES STARTING AT MIDNIGHT TONIGHT.

WEDNESDAY...SMALL CRAFT REMAINS IN EFFECT THROUGH MIDDAY
WEDNESDAY, THEN SEAS ARE EXPECTED TO SUBSIDE.

WEDNESDAY NIGHT-FRIDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED.

FRIDAY NIGHT-SATURDAY...INCREASING WINDS OVERNIGHT INTO SATURDAY
AND SATURDAY NIGHT AS A COASTAL LOW STRENGTHENS. AT LEAST SMALL
CRAFT CONDITIONS EXPECTED, WITH GALE FORCE WINDS POSSIBLE.

&&

.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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