Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 162243
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
543 PM EST TUE DEC 16 2014

.SYNOPSIS...
LOW PRESSURE IN THE GREAT LAKES WILL PUSH A WARM FRONT NORTH INTO
THE MID ATLANTIC STATES THIS EVENING, WITH SECONDARY LOW PRESSURE
FORMING NEAR LONG ISLAND BY MIDNIGHT. THE COLD FRONT PASSES OFFSHORE
WEDNESDAY MORNING AS THE LOWS COMBINE AND ARRIVE OVER THE CANADIAN
MARITIMES THURSDAY. HIGH PRESSURE IN THE GREAT LAKES ASSERTS CONTROL
HERE LATER ON FRIDAY. LOW PRESSURE IN GEORGIA SATURDAY IS FORECAST
TO INTENSIFY AS IT MOVES NORTHEASTWARD OFF THE MID ATLANTIC COAST
SUNDAY. WEAK HIGH PRESSURE FOLLOWS MONDAY BEFORE A STRONG LOW
PRESSURE SYSTEM DEVELOPS OVER THE MISSISSIPPI VALLEY NEXT TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
THE WATER VAPOR IMAGERY THIS EVENING SHOWS A CLOSED LOW LIFTING
NORTHEASTWARD FROM THE UPPER OHIO VALLEY. THIS FEATURE WILL CONTINUE TO
TRACK NORTHEASTWARD THROUGH TONIGHT WHILE TAKING ON A NEGATIVE
TILT. THE LARGE SCALE LIFT HAS BEEN FOCUSED IN A NARROWING RIBBON
OF SHOWERS NOW PRESSING OFFSHORE. THERE ARE SOME OTHER SHOWERS
FARTHER WEST BUT THESE ARE TENDING TO BE SCATTERED OR IN SMALL
CLUSTERS. ANOTHER AREA OF SHOWERS IN CENTRAL PENNSYLVANIA IS WITH
THE CLOSED LOW, HOWEVER THESE MAY TEND TO WEAKEN SOME AS THEY LIFT
EAST- NORTHEASTWARD AS FORCING WEAKENS A LITTLE. AS A RESULT, THE
POPS WERE ADJUSTED BASED ON RADAR TRENDS.

OTHERWISE, LOW PRESSURE WILL TRACK TO OUR NORTHWEST AND A SECONDARY
LOW IS FORECAST TO DEVELOP OFFSHORE OVERNIGHT. THE ASSOCIATED COLD
FRONT WILL EVENTUALLY ARRIVE LATE. UNTIL THE COLD FRONT ARRIVES, A
DECENT AMOUNT OF LOW-LEVEL MOISTURE IS FORECAST TO REMAIN IN PLACE
AND DESPITE THE WINDS SHIFTING EVENTUALLY TO THE SOUTHWEST AND WEST,
IT MAY TAKE QUITE A BIT OF TIME FOR THE CLOUDS TO THIN. WE SHOULD
ALSO HAVE SOME FOG AROUND, ALTHOUGH WE HAVE LESS CONFIDENCE
REGARDING DENSE FOG DEVELOPMENT.

THE HOURLY GRIDS WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS, AND
THE LAMP/LAV GUIDANCE WAS BLENDED IN THROUGH THIS EVENING. OVERALL,
NO MAJOR CHANGES WERE MADE OTHER THAN TO THE POPS.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
LOW PRESSURE WILL CONTINUE TO LIFT TO OUR NORTHEAST AND STRENGTHEN
AS IT MOVES INTO THE GULF OF MAINE DURING THE DAY. THIS WILL LEAD TO
A STRONG NORTHWEST FLOW ACROSS THE AREA DURING THE DAY, WITH GUSTS
OF AT LEAST 20-25 MPH, WITH SOME GUSTS AROUND 30 MPH POSSIBLE. SKIES
WILL LIKELY REMAIN PARTLY TO MOSTLY CLOUDY MOST OF THE DAY ACROSS
MUCH OF THE AREA. IT IS ALSO POSSIBLE THAT THERE MAY BE ENOUGH
MOISTURE AND LOW-LEVEL LIFT THAT A FEW ISOLATED SHOWERS MAY AFFECT
OUR FAR NORTHERN COUNTIES. IF ANY SHOWERS DID OCCUR, RIGHT NOW THEY
ARE EXPECTED TO BE MOSTLY RAIN, EXCEPT ACROSS THE POCONOS WHERE
THERE COULD BE SOME SNOW SHOWERS LATER IN THE DAY.

HIGHS WERE A BLEND OF MAV/MET MOS AND MOSGUIDE WHICH WERE IN PRETTY
GOOD AGREEMENT.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
500 MB (JETSTREAM): LOW PRESSURE OVER EASTERN NYS WILL MOVE TO THE
MARITIMES THURSDAY. A TROUGH OF SEVERAL SHORT WAVES CURRENTLY
APPROACHING CALIFORNIA REACHES THE SOUTHERN PLAINS FRIDAY MORNING
AND SLIDES OFF THE MID ATLANTIC COAST SUNDAY. A HIGH AMPLITUDE
TROUGH SHOULD BE ORGANIZING OVER THE MISSISSIPPI VALLEY NEXT
TUESDAY.

TEMPERATURES: CALENDAR DAY AVERAGES ABOUT 5 DEGREES ABOVE NORMAL
THURSDAY, THEN 2 TO 5 DEGREES ABOVE NORMAL EACH DAY FROM FRIDAY
THROUGH NEXT TUESDAY. THE OPERATIONAL ECMWF APPEARS TO HAVE BEEN
BIASED TOO COOL IN PREVIOUS FORECASTS AND AM DISCARDING MUCH OF
THE COLD BIAS...LEANING MORE HEAVILY ON THE 12Z/16 GFS.

FORECAST BASIS: IN A NUTSHELL AND UNLESS OTHERWISE NOTED WITHIN
THE DAILIES. THIS FORECAST IS A 50 50 BLEND OF THE 12Z/16 MAV/MET
FOR WEDNESDAY NIGHT-THURSDAY NIGHT. USED THE WARMER OF THE NCEP
TEMPERATURE GUIDANCE, ESPECIALLY AT NIGHT. THURSDAYS TEMPS MIGHT
BE 2-3 DEGREES WARMER THAN CURRENTLY FCST. THE 12Z/16 MEX MOS WAS
APPLIED FRIDAY AND FRIDAY NIGHT (BLENDED LOWER WITH THE PRIOR PHI
FCST BUT IT APPEARS PRIOR ECMWF 2M TEMPERATURES HAVE BEEN FORECAST
TOO LOW FOR THURSDAY- FRIDAY. 1522Z/16 WPC D4-8 ELEMENTS OF
DEWPOINTS/WIND/SKY/POP/ MAX-MIN TEMPS WERE USED. HAVE BLENDED THE
WPC DAYTIME MAX`S WARMER USING THE 12Z/16 GFS ON ALL DAYS THURSDAY
- SUNDAY. SREF AND GEFS PROBS FOR QPF AND 12Z/16 ECMWF 2METER
TEMPERATURES WERE CHECKED FOR THIS FORECAST BUT NOT DIRECTLY
APPLIED. THE GEFS POPS APPEAR TOO CONSERVATIVE FOR SATURDAY NIGHT-
SUNDAY MORNING WHEN COMPARED TO THE AMPLITUDE OF THE SHORT WAVE
TROUGH CROSSING THE MID ATLANTIC COAST SUNDAY MORNING.

THE DAILIES...

WEDNESDAY NIGHT...LOW PRESSURE ALOFT DEPARTING EASTWARD FROM NYS HAS
A LEFTOVER FINAL SHORT WAVE DEPICTED AT 500MB OF ABOUT A 90M 12 HR
HFC CROSSING E PA WHICH SHOULD SET OFF SOME SNOW SHOWERS OR
FLURRIES UP NORTH OF I80. OTHERWISE...PARTLY CLOUDY. W-NW WIND
GUST 20-25 KT AT TIMES.

THURSDAY - FRIDAY...DRYING TREND CONTINUES WITH ZONAL-ISH FLOW ALOFT
FORMING BY FRIDAY AND NOT MUCH MOISTURE TO WORK WITH. GREAT LAKES
SNOW SHOWERS MAY LEAK DOWN INTO THE POCONOS BOTH DAYS WHERE CONSIDERABLE
CLOUDINESS EXISTS. OTHERWISE PARTLY CLOUDY TO CLEAR AND COOLER WITH
18Z 850 TEMPS ABOUT 4C COLDER (NEAR -6C) THAN THOSE VALUES OF 18Z
WED (NEAR -2C). NW WINDS GUST 20-25 MPH THURSDAY AND NEAR 20 MPH
FRIDAY.

SATURDAY - SUNDAY...ONE LAST DAY, OR AT LEAST HALF DAY, OF TRANQUILITY
ON SATURDAY BEFORE EAST COAST LOW PRESSURE NEARS FROM THE SOUTH-
SOUTHWEST. DEPENDING ON THE QUICKNESS AND POSITION OF THE NORTHERN
STREAM ENERGY, HELPING TO DEVELOP GULF COAST SURFACE INFLECTION,
DICTATES HOW FAST PRECIPITATION OVERSPREADS FROM THE SOUTH LATER
ON SATURDAY. IT IS STILL TOO EARLY TO GO INTO TOO MUCH DEPTH WITH
THIS SYSTEM GIVEN THE AMOUNT OF SPREAD THAT WE ARE STILL SEEING.
ONE THING THAT IS INDICATED TO WPC AND MYSELF IS ABOVE AVERAGE
CONFIDENCE FOR PRECIPITATION TO SPREAD INTO OUR AREA SATURDAY
NIGHT. THERMAL PROFILES LOOK MARGINAL FOR MUCH IF ANY SNOW SE OF
I95... MAYBE A MIX IN THE 195 CORRIDOR AND COLD ENOUGH FOR SNOW NW
OF I95. THE VORT MAX LOOKS PRETTY STRONG...EVEN WITH THE GEFS 50
METER SPREAD IN 500MB HEIGHTS OVER NJ 12Z SUNDAY.

MONDAY...VARIABLE SOLUTIONS FROM MOSTLY SUNNY AND NICE TO LOTS OF
LEFTOVER CLOUDS AS A WEAK RIDGE OF HIGH PRESSURE FROM DIXIE EDGES
NORTHEAST OVER AREA. AM CONCERNED THERE WILL BE ALOT MORE LOW
CLOUDINESS BELOW A POSSIBLE INVERSION, THAN CURRENTLY ADVERTISED.

TUESDAY...CLOUDINESS BECOMING DOMINANT AND CHANCE OF SHOWERS AS THE
MISSISSIPPI VALLEY TROUGH DEVELOPS EASTWARD.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

TONIGHT...VARYING CONDITIONS OF VFR/MVFR AND LOCALLY IFR. THE
CEILINGS SHOULD SETTLE TO MVFR/IFR BEFORE SOME THINNING OCCURS LATE.
SOME SHOWERS WILL CONTINUE INTO THE OVERNIGHT HOURS, WITH LOCALLY
REDUCED VISIBILITIES AT TIMES. THE LOCAL VISIBILITIES WILL ALSO BE
REDUCED FOR AWHILE DUE TO SOME FOG. SOUTHEAST WINDS AROUND 5 KNOTS,
BECOMING LIGHT/VARIABLE OR SOUTHWEST THEN WEST-NORTHWEST LATE.

WEDNESDAY...ANY MVFR OR LOWER CONDITIONS EARLY ARE EXPECTED TO
IMPROVE TO VFR. WEST-NORTHWEST WINDS INCREASING TO 10-15 KNOTS
WITH GUSTS TO 20-25 KNOTS.

OUTLOOK...
WEDNESDAY NIGHT...VFR SCT CLOUDS AOA 4000 FT EXCEPT POSSIBLE MVFR
CONDS OVER THE POCONOS IN SCATTERED SNOW SHOWERS. NW WIND GUST
20-25 KT AT TIMES. CONFIDENCE: ABOVE AVERAGE.

THURSDAY AND FRIDAY...VFR SCT-BKN AOA 3500 FT EXCEPT POSSIBLE MVFR
CONDS IN SNOW SHOWERS OVER THE POCONOS. NORTHWEST WINDS SUSTAINED
10-15KT WITH GUSTS NEAR 25KT.  CONFIDENCE: ABOVE AVERAGE.

SATURDAY...VFR CIRRUS AND LIGHT WIND TO START THEN CIGS NEAR 3000 FT
POSSIBLE LATE DAY OR NIGHT AS THE WIND TURNS NE AND PCPN DEVELOPS
AT NIGHT. CONFIDENCE: ONLY AVERAGE BECAUSE OF THE UNCERTAIN TIMING
OF LOWERING CIGS AND ALSO PTYPE UNCERTAINTY.

SUNDAY...MVFR OR BRIEF IFR CONDS IN MORNING SNOW/RAIN THEN IMPROVING
CONDITIONS DURING MIDDAY. NORTH OR NORTHEAST WIND BECOMING NORTHWEST.
CONFIDENCE: ABOVE AVERAGE ON PCPN BUT BELOW AVERAGE ON PRECIPITATION
TYPE AND TIMING THE IMPROVING CONDITIONS.

&&

.MARINE...
SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED ACROSS THE WATERS
TONIGHT AS A WARM FRONT BEGINS TO LIFT ACROSS THE AREA. SOUTHEAST
WINDS EARLY WILL BECOME VARIABLE AS AN AREA OF LOW PRESSURE DEVELOPS
ALONG THE FRONT OVERNIGHT, BEFORE BECOMING WEST TO NORTHWEST BY
DAYBREAK WEDNESDAY AS THE LOW MOVES TO OUR NORTHEAST. A SMALL CRAFT
ADVISORY IS NOW IN EFFECT STARTING WEDNESDAY MORNING AS WINDS ARE
EXPECTED TO INCREASE TO 25-30 KNOTS AS THE LOW STRENGTHENS AS IT
MOVES INTO THE GULF OF MAINE.

OUTLOOK...
WEDNESDAY NIGHT AND THURSDAY...WHILE SEAS ARE EXPECTED TO REMAIN
GENERALLY BELOW SCA LEVELS, NORTHWEST WIND GUSTS SHOULD REACH THE
SCA THRESHOLD OF 25 KNOTS AT TIMES WEDNESDAY NIGHT THROUGH THURSDAY
OR THURSDAY EVENING...POSSIBLY 30 KT. SCA IS POSTED EXCEPT FOR DE
BAY WHERE UNCERTAINTY EXISTS ON MAX GUSTS. I RAISED WW3 ATLANTIC SEAS
BY 1 FOOT 00Z THU-18Z THU. CONFIDENCE: ABOVE AVERAGE FOR THE SCA SCENARIO.

FRIDAY...MOSTLY SUB-ADVISORY CONDITIONS ARE EXPECTED. SOME NORTHWEST
WIND GUSTS COULD STILL BE IN THE 20 PLUS KNOT RANGE, THOUGH.
CONFIDENCE: ABOVE AVERAGE.

SATURDAY...MODEL TRENDS SINCE YESTERDAY ARE LOWER ON THE EXPECTED
WINDS. EITHER NO HAZARD OR POSSIBLE SCA. CONFIDENCE: AVERAGE.

SUNDAY...SCA MAY DEVELOP IN THE WAKE OF THE DEPARTING COASTAL LOW.
CONFIDENCE: AVERAGE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 AM WEDNESDAY TO 5 PM EST THURSDAY
     FOR ANZ450>455.
     SMALL CRAFT ADVISORY FROM 7 AM TO 6 PM EST WEDNESDAY FOR
     ANZ430-431.

&&

$$
SYNOPSIS...DRAG
NEAR TERM...GORSE
SHORT TERM...ROBERTSON
LONG TERM...DRAG
AVIATION...DRAG/GORSE
MARINE...DRAG/ROBERTSON




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