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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 140023
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
723 PM EST FRI DEC 13 2013

.SYNOPSIS...
-- Changed Discussion --
A WEAK COLD FRONT IN NORTHERN PENNSYLVANIA WILL SINK SOUTHWARD THROUGH
MUCH OF PENNSYLVANIA AND THE NORTHERN HALF OF NEW JERSEY OVERNIGHT.
STRONG HIGH PRESSURE IN SOUTHERN CANADA WILL BUILD TOWARD MAINE ON
SATURDAY. LOW PRESSURE IN THE TEXAS PANHANDLE WILL TURN NORTHEAST
AND PASS OFF THE MID ATLANTIC COAST LATE SATURDAY NIGHT AND STRENGTHEN
AS IT MOVES TO NOVA SCOTIA LATE SUNDAY. A CLIPPER LOW WILL MOVE
NORTH OF THE AREA TUESDAY, PASSING A COLD FRONT ACROSS OUR AREA.
HIGH PRESSURE WILL THEN BUILD INTO OUR AREA FROM THE SOUTHWEST
WEDNESDAY INTO THURSDAY, THEN OFF THE COAST BY THURSDAY NIGHT.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --
RUC/HRRR PRIMARILY USED FOR THIS FCST AND ITS QUIET. A COLD FRONT
FROM BOSTON TO SCRANTON THIS EVENING IS PRESSING SOUTHWARD AS
STRONG HIGH PRESSURE EASES EASTWARD ACROSS SOUTHERN CANADA AND
BUILDS A LARGE RESERVOIR OF VERY COLD SUB FREEZING AIR TO OUR NORTH AND
NORTHEAST. THIS TO BE TAPPED SATURDAY AND SATURDAY NIGHT BY THE
APPROACHING SOUTHERN STATES LOW PRESSURE SYSTEM. THAT COLD FRONT
ANS DOME OF COLD HIGH PRESSURE TO OUR NORTH IS SETTING THE STAGE
FOR WHAT WILL BE A SIGNIFICANT WINTER SNOW STORM FOR MUCH OF
EASTERN PENNSYLVANIA AND NORTHERN NEW JERSEY.

THAT FRONT WILL HAVE SOME FLURRIES ALONG IT AND IS THE FIRST
EASIER LIFT ZONE (COLDER DENSER AIRMASS) FOR TOMORROW MORNINGS
SNOW OUTBREAK WHICH MAY ALREADY BE DUSTING I80 NORTHWARD WITH
SEVERAL TENTHS OF AN INCH OF FLUFFY SNOW.

THE 630 PM ESTF WARMED TEMPS SLIGHTLY OVERNIGHT DUE TO CLOUD
COVER AND TEMPS RUNNING WARRING WARM THAN FORECAST LATE TODAY.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
SATURDAY: THE 630 PM ESTF RAN WX GRIDS USING THE BOX WX TOOL AND
BLENDED 18Z NAM/GFS/12Z ECMWF PARTIAL THICKNESSES. ITS ADDED SNOW
TO THE FCST IN SOUTHERN NEW JERSEY AND DELAYED THE CHANGE THERE.

THE 930 PM ESTF IS LIKELY TO DELAY THIS CHANGEOVER FURTHER. THE
COLD AIR DAMMING WILL BE LARGE SINCE THE 850 FLOW ONLY TURNS SOUTHEAST
AND NOT SOUTHWEST UNTIL THE PRIMARY LIFT AND GOB OF HEAVIER QPF HAS
PASSED BY TO OUR NORTHEAST BETWEEN 03Z-07Z/15.

A CONCERN IS NOT MUCH HAPPENING S OF I-80 SATURDAY MORNING
ALLOWING EASIER COASTAL PLAIN WARMING THERE.

SNOW GROWTH SHOULD BE BRIEFLY BE S/S+ VARIETY IN THE 21Z-02Z TIME
FRAME FROM KPHL NORTH. SNOW WATER RATIOS WILL MAKE THIS A MUCH
FLUFFIER SNOWFALL FOR THE REGION NEAR AND N I78...ESPECIALLY I80
REGION. OUR SNOW TOTAL MAY NEED TO BE SLIGHTLY INCREASED ALONG AND N
OF I-80 TO AROUND 10 INCHES BUT AM NOT LIKELY TO INITIATE THAT
INCREASE ON THIS SHIFT DUE TO MODEL UNCERTAINTY AND WE ALREADY
HAVE A WARNING OF 6-8 INCHES GOING. I DONT ANTICIPATE MUCH SLEET OR
FREEZING RAIN NORTH OF I-80...MORE LIKELY A FREEZING DRIZZLE AFTER
THE PRIMARY LIFT PASSES THAT REGION AFTER 06Z.

AN HOUR OR TWO OF SNOWFALL 1-2"/HOUR IS ANTICIPATED IN E PA AND NNJ
NEAR 00Z/15.

WSW IS POSTED AND HOLDS FOR NOW.


BELOW FROM THIS AFTNS DISCUSSION

THE MAIN EVENT BEGINS SOMETIME SATURDAY MORNING AND WILL CONTINUE
MUCH OF SATURDAY NIGHT. TEMPS AT THE SURFACE AND ALOFT SHOULD BE
BELOW FREEZING TO START SO PRECIP SHOULD BEGIN AS SNOW EVERYWHERE.
PRECIP WILL START OUT LIGHT AND GRADUALLY INCREASE IN INTENSITY
DURING THE MORNING...OVERSPREADING THE AREA FROM WEST TO EAST.
INCREASING ONSHORE/ELY WINDS WILL CAUSE SFC TEMPS TO RISE ABOVE
FREEZING FROM THE ATLANTIC COAST NORTHWEST DURING THE MORNING. THE
RAIN/SNOW LINE SHOULD CONTINUE NWWD TO NEAR THE FALL LINE DURING
THE AFTERNOON.

THE NAM AND GFS INDICATE STRONGEST UVV DURING THE LATE AFTERNOON
THROUGH EVENING PERIOD AND THIS IS WHEN THE HEAVIEST PRECIP RATES
ARE EXPECTED TO OCCUR. MODELS ALSO INDICATE A WARM LAYER...IE ABOVE
FREEZING...ABOVE THE SFC PUSHING QUICKLY NWD DURING THE EVENING AND
OVERNIGHT. WITH COLD AIR EXPECTED TO HOLD AT THE SFC DUE TO
AFORE-MENTIONED CANADIAN HIGH PRES...SNOW SHOULD CHANGE OVER TO
FREEZING RAIN FOR MOST AREAS BY AROUND 06Z...EXCEPT PERHAPS THE
POCONOS AND FAR NW NJ. SIGNIFICANT ICING...A QUARTER INCH OR MORE...
IS POSSIBLE FOR SOME AREAS IN THE WINTER STORM WARNING. ALSO...THERE
IS A POTENTIAL FOR FRONTO-GENESIS AND PRECIP BANDING DURING THE
EVENING AND HENCE SOME LOCALLY HIGHER SNOWFALL AMOUNTS.

THE ASSOCD SFC LOW IS FCST TO DEEPEN RATHER RAPIDLY AS IS MOVES BY
JUST SE OF DE OVER NIGHT. HOWEVER IT IS MOVG QUICKLY AND IS FCST TO
BE S OF CAPE COD BY 12Z SUNDAY. MOST PRCIP SHOULD BE OVER BY THAT
TIME WITH COLD ADVECTION AND INCREASING NW WINDS BEHIND THE LOW.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
THE STORM SYSTEM THAT WILL BE AFFECTING THE AREA SATURDAY INTO
SATURDAY NIGHT WILL CONTINUE TO MOVE TO OUR NORTHEAST AND STRENGTHEN
AS IT MOVES THROUGH THE NEW ENGLAND COASTAL WATERS AND INTO THE
CANADIAN MARITIMES. THERE COULD BE SOME LINGERING PRECIPITATION
EARLY IN THE MORNING SUNDAY AS SOME WRAP AROUND MOISTURE AFFECTS THE
AREA BEFORE PULLING AWAY AND CUTTING OFF PRECIPITATION. THE
REMAINDER OF THE DAY SUNDAY SHOULD REMAIN PRECIP FREE AND CLOUDS
SHOULD BEGIN TO SCATTER OUT. THIS MAY ALLOW FOR SOME WARMING DURING
THE DAY, BUT HIGHS SHOULD STILL REMAIN BELOW NORMAL. A STEADY
NORTHWEST FLOW WILL DEVELOP ACROSS THE AREA AND REMAIN BREEZY INTO
SUNDAY NIGHT. OVERNIGHT LOWS SUNDAY WILL BE QUITE COLD AND BELOW
NORMAL AGAIN. WITH THE NORTHWEST FLOW, WIND CHILLS WILL DROP INTO
THE TEENS AND SINGLE DIGITS, EVEN MINUS SINGLE DIGITS FOR COLDEST
AREAS.

HIGH PRESSURE WILL BUILD OVER THE MID-ATLANTIC MONDAY INTO MONDAY
NIGHT. WE EXPECT A PRECIPITATION FREE FORECAST INTO THE EARLY PART
OF MONDAY NIGHT AS MOISTURE WILL BE LACKING. HOWEVER, AS WE MOVE
INTO THE LATTER HALF OF MONDAY NIGHT INTO TUESDAY, MOISTURE
INCREASES ACROSS THE AREA WHILE A CLIPPER TYPE SYSTEM MOVES THROUGH
THE GREAT LAKES REGION AND ACROSS THE NORTHERN TIER OF THE COUNTRY.
THIS MAY PULL A FRONTAL BOUNDARY INTO OUR AREA, WHILE A FEW SHORT
WAVES/VORTICITY IMPULSES MOVE ACROSS THE AREA AS WELL. THESE COULD
INTERACT WITH EACH OTHER AND CREATE SOME SHOWER ACTIVITY. THE
PRECIPITATION SHOULD MAINLY BE SNOW ACROSS THE NORTHERN HALF OF THE
AREA WITH RAIN AND SNOW POSSIBLE FOR THE SOUTHERN HALF.

ANY PRECIPITATION SHOULD DIMINISH OVERNIGHT AS THE SYSTEM MOVES TO
OUR NORTHEAST. A STEADY NORTHWEST FLOW WILL DEVELOP ON WEDNESDAY IN
BETWEEN THE DEPARTING LOW TO OUR NORTHEAST AND HIGH PRESSURE
BEGINNING TO NOSE IT`S WAY IN FROM THE SOUTHWEST. WEDNESDAY INTO
THURSDAY SHOULD BE PRECIPITATION FREE AS HIGH PRESSURE BUILDS ACROSS
THE EAST COAST ON WEDNESDAY NIGHT AND PUSHES OFFSHORE BY THURSDAY
NIGHT.

A FRONTAL BOUNDARY WILL BE APPROACHING THE AREA LATE IN THE WEEK OR
POSSIBLY NEXT WEEKEND. WITH THE UNCERTAINTY THIS FAR OUT AND THE
DIFFERENCES IN MODEL GUIDANCE, WE INTRODUCE A CHANCE OF SHOWERS TO
THE FORECAST STARTING FRIDAY. IT LOOKS LIKE IF THE PRECIPITATION
HOLDS OUT LONG ENOUGH, IT COULD BE RAIN FOR MOST AREAS, ALTHOUGH
THERE WILL REMAIN A CHANCE OF SNOW, OR A MIX FOR OUR COLDEST SPOTS.

A RETURN TO CLOSER TO NORMAL TEMPERATURES BEGIN TUESDAY AND CONTINUE
INTO THURSDAY, BEFORE THE POSSIBILITY OF A RETURN OF ABOVE NORMAL
TEMPERATURES BY FRIDAY.

&&

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

TONIGHT...VFR CIRRUS LOWERS TO CIGS AOA 4000 FT BY 12Z. MVFR OR
IFR SNOW BREAKS OUT AFTER 10Z ALONG AND N OF 180.

SATURDAY AND SATURDAY NIGHT...VFR CIGS EVENTUALLY DEGRADE TO IFR CONDS
IN SNOW THEN A TRANSITION TO SLEET/RAIN FROM KPHL/KTTN SOUTHEASTWARD
SOMETIME SAT AFTN OR EVENING AS PER TAFS. KRDG/KABE MAY REMAIN MOSTLY
SNOW WITH A LITTLE SLEET MIX TOWARD 03Z/15 AND END AS FREEZING MIST.
PLOWING ENVISIONED AS BEING NEEDED FOR KRDG/KABE... AND PROBABLY
DOWN THRU KPHL. THE QUICKEST CHANGE TO RAIN KMIV AND KACY.

NE WIND AROUND 10 KT EXCEPT GUSTY E WIND 20 KT ANTICIPATED VCNTY
KACY LATE IN THE DAY AND EVENING. WIND TURNING N AND NW EVERYWHERE
LATE SAT NIGHT KEEPING COLD SUBFREEZING SURFACE AIR TUCKED INTO OR
REINTRODUCING IT MANY TAFS SITES VCNTY KPNE-KTTN NORTHWARD.


OUTLOOK...
SUNDAY...MVFR CONDITIONS POSSIBLE EARLY, IMPROVING THROUGH THE
DAY, WITH A FEW SHOWERS POSSIBLE EARLY. NORTHWEST WINDS, POSSIBLY BECOMING
GUSTY IN AFTERNOON AROUND 20-25 KT.

SUNDAY NIGHT-MONDAY NIGHT...MOSTLY VFR. GUSTY W-NW WINDS 15-20 KT
MONDAY AFTERNOON.

TUESDAY...MOSTLY VFR, POSSIBLE MVFR, MAINLY NORTHERN AIRPORTS IF
SNOW SHOWERS OCCUR.

TUESDAY NIGHT-WEDNESDAY...MOSTLY VFR. GUSTY W-NW WINDS 20-25 KT
POSSIBLE WEDNESDAY AFTERNOON.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
TONIGHT...WEST WIND SHIFTING N OR NE BY MORNING...GUSTS UNDER 20 KT.

SATURDAY-SATURDAY NIGHT...SCA ISSUED. SMALL CHC WE WILL NEED TO BUMP
UP TO GALE...ESPECIALLY NNJ WATERS IN RESPONSE TO THE STRONG COLD
HIGH NEAR MAINE AND UNSTABLE BOUNDARY LAYER ALLOWING CONSIDERABLE
TRANSFER OF TIGHTENING GRADIENT INFLOW ENE WINDS.


OUTLOOK...
SATURDAY NIGHT-SUNDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS
EXPECTED AS LOW PRESSURE MOVES ACROSS THE WATERS SATURDAY NIGHT, AND
NORTHWEST FLOW DEVELOPS BEHIND THE DEPARTING SYSTEM.

MONDAY-MONDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS POSSIBLE
EARLY, BEFORE DIMINISHING AS HIGH PRESSURE BUILDS ACROSS THE WATERS
LATER IN THE DAY.

TUESDAY-WEDNESDAY...A RETURN TO ADVISORY LEVEL WINDS POSSIBLE BEHIND
A QUICK MOVING FRONTAL BOUNDARY ON TUESDAY.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER STORM WARNING FROM 7 AM SATURDAY TO 5 AM EST SUNDAY FOR
     PAZ054-055-060>062-101-103-105.
     WINTER WEATHER ADVISORY FROM 7 AM SATURDAY TO 5 AM EST SUNDAY
     FOR PAZ070-071-102-104-106.
NJ...WINTER STORM WARNING FROM 7 AM SATURDAY TO 5 AM EST SUNDAY FOR
     NJZ001-007>010.
     WINTER WEATHER ADVISORY FROM 7 AM TO 5 PM EST SATURDAY FOR
     NJZ013-016>019.
     WINTER WEATHER ADVISORY FROM 7 AM SATURDAY TO 5 AM EST SUNDAY
     FOR NJZ012-015.
DE...WINTER WEATHER ADVISORY FROM 7 AM TO 5 PM EST SATURDAY FOR
     DEZ001.
MD...WINTER WEATHER ADVISORY FROM 7 AM SATURDAY TO 5 AM EST SUNDAY
     FOR MDZ008.
MARINE...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 5 AM EST MONDAY FOR
     ANZ430-431-450>455.

&&

$$
SYNOPSIS...ROBERTSON/DRAG 724
NEAR TERM...AMC/DRAG 724
SHORT TERM...AMC/DRAG 724
LONG TERM...ROBERTSON
AVIATION...DRAG/KLINE/ROBERTSON 724
MARINE...AMC/DRAG/ROBERTSON 724