Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 290135
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
935 PM EDT TUE OCT 28 2014

.SYNOPSIS...
A COLD FRONT WILL MOVE FROM WEST TO EAST INTO THE REGION
OVERNIGHT AND THEN WILL MOVE OFFSHORE ON WEDNESDAY. HIGH PRESSURE
WILL BUILD INTO THE REGION FROM THE OHIO VALLEY WEDNESDAY NIGHT
AND THURSDAY. BY FRIDAY TWO LOW PRESSURE SYSTEMS WILL START TO
IMPACT OUR REGION, ONE OVER THE GREAT LAKES AND ANOTHER OFF THE
CAROLINA COASTLINE. THESE AREAS OF LOW PRESSURE WILL BE LOCATED
OFFSHORE ON SATURDAY. BY SUNDAY THE STRENGTHENING LOW PRESSURE
SYSTEM WILL CONTINUE MOVING NORTHEAST OFF THE NEW ENGLAND
COASTLINE. HIGH PRESSURE WILL BUILD BACK INTO THE REGION FOR
MONDAY AND TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
THE MID LEVEL RIDGE WILL CONTINUE TO DRIFT EASTWARD AND OUT OVER
THE WESTERN NORTH ATLANTIC OVERNIGHT. MEANWHILE, A TROUGH WILL
APPROACH SLOWLY FROM THE WEST.

A SURFACE COLD FRONT EXTENDED ACROSS THE EASTERN GREAT LAKES AND
THE UPPER OHIO RIVER VALLEY THIS EVENING. THE BOUNDARY WILL
CONTINUE TO PROGRESS EASTWARD AND IT IS FORECAST TO BE LOCATED
ALONG THE INTERSTATE 81 CORRIDOR THROUGH PENNSYLVANIA, MARYLAND
AND VIRGINIA AROUND DAYBREAK.

A BAND OF RAIN SHOWERS ALONG AND BEHIND THE FRONT IS EXPECTED TO
MOVE INTO OUR NORTHWESTERN COUNTIES LATE TONIGHT.

WE ARE ANTICIPATING A LIGHT WIND, FAVORING THE SOUTH AND
SOUTHWEST IF ANY DIRECTION AT ALL. CLOUDS WILL BE ON THE INCREASE
AND MINIMUM TEMPERATURES SHOULD BE MILD FOR THIS TIME OF THE YEAR,
RANGING MAINLY IN THE 50S.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
THE COLD FRONT IS FORECAST TO PASS ACROSS THE REMAINDER OF OUR
AREA AND OFF THE COAST ON WEDNESDAY MORNING. THE BAND OF SHOWERS
IS EXPECTED TO TRAIL THE BOUNDARY AND WE WILL CONTINUE TO MENTION
A CHANCE OF SHOWERS THROUGH MUCH OF THE DAY. RAINFALL AMOUNTS
SHOULD BE MAINLY LESS THAN A QUARTER INCH.

A SOUTHWEST WIND AROUND 6 TO 12 MPH IN THE MORNING IS EXPECTED TO
VEER TO THE WEST NORTHWEST FOLLOWING THE COLD FRONTAL PASSAGE.
AFTERNOON TEMPERATURES SHOULD BE ABOUT 5 TO 7 DEGREES ABOVE
NORMAL.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
WEDNESDAY NIGHT: A FRONTAL BOUNDARY WILL BE OFFSHORE TO START THE
PERIOD WHICH SHOULD RESULT IN CLEARING CONDITIONS, PERHAPS A FEW
SHOWERS STILL ALONG THE COAST EARLY. WINDS SHIFTING TO NORTHWEST
BEHIND THE FRONT. TEMPERATURES A COMPROMISE BETWEEN THE 12Z GFS
AND THE MAV/MET GUIDANCE.

THURSDAY THROUGH FRIDAY: HIGH PRESSURE BUILDS OVER THE REGION.
DRY. GENERAL NORTHWEST FLOW TILL THE HIGH PASSES BY LATE FRIDAY.
EVEN WITH TEMPERATURES THURSDAY MORNING STILL IN THE LOW TO MID
40`S WITH NORTHWEST FLOW THIS FORECAST DOES UNDERCUT MAV/MET BY A
COUPLE OF DEGREES FOR HIGHS THURSDAY (MID-UPPER 50`S). FOR FRIDAY,
USING THE 925 MB TEMPS WOULD YIELD HIGHS IN THE UPPER 50`S AT PHL
ON FRI, THOUGH THINKING WITH CLOUDS AND A LOWER SUN ANGLE THIS
SHOULD BE KNOCKED BACK TILL ABOUT THE MID 50`S. COOLER NW BOTH
DAYS.

 FRIDAY NIGHT THROUGH SUNDAY NIGHT:

* STRONG WINDS AND POSSIBLE COASTAL STORM SATURDAY*

STORM OVERVIEW: TWO LOW PRESSURE CENTERS WILL BE MOVING TOWARD
THE REGION TO START OFF THIS PERIOD. ONE NEAR DETROIT AND THE
OTHER OFF HATTERAS. AN UNDERSTATEMENT WOULD BE THAT THE MODELS AND
THE RESPECTIVE ENSEMBLES HAVE BEEN GOING BACK AND FORTH ON THE
OUTCOME. MANY OF THE KEY PLAYERS INVOLVED ARE STILL NOT FIRMLY IN
THE UPPER AIR NETWORK TO WHICH MORE SAMPLED DATA WILL BECOME
AVAILABLE. THIS MAY REDUCE SOME UNCERTAINTY OVER THE NEXT DAY OR
TWO. THE MODEL SPREAD FROM THE GEFS, ECMWF, CMC, UKMET AND VARIOUS
ENSEMBLE PACKAGES SHOW TWO MAIN OUTCOMES. THE FIRST IS FOR A
FRONTAL PASSAGE WITH JUST SOME RAIN SHOWERS WITH THE NORTHERN WAVE
COMING EAST THROUGH THE REGION ON SATURDAY FOLLOWED BY A QUICK BUT
POTENT COLD SHOT WITH INTERACTION BETWEEN THE LOWS WELL TO OUR
EAST AND DISORGANIZED. THIS OUTCOME HAS BEEN GAINING TRACTION
TODAY WITH MOST DAY OPERATIONAL MODEL RUNS. POSSIBILITY NUMBER TWO
INVOLVES MORE INTERACTION BETWEEN THE LOW OFFSHORE AND THE LOW
MOVING EAST OUT OF THE GREAT LAKES (00Z ECMWF). THIS WOULD RESULT
IN A RAINER AND COOLER DAY WITH THE OUTSIDE POSSIBILITY OF RAIN
CHANGING TO SNOW DUE TO DYNAMICAL COOLING. EITHER WAY FRIDAY NIGHT
LOOKS DRY STILL WITH INCREASING CLOUDS AND LIGHT WINDS. SATURDAY
WILL FEATURE RAIN SHOWERS AND WINDY CONDITIONS AS THE LOW
PRESSURE(S) ORGANIZE AND STRENGTHEN. THE PRECIPITATION MAY BE
MIXED AT TIMES AS WELL WITH SNOW DEPENDING ON THE EXACT OUTCOME.
BY SUNDAY WRAP- AROUND PRECIPITATION WILL END WITH CLEARING BUT
STILL WINDY AND COOL.

THE WINDS WILL BE THE MAIN IMPACT FROM THIS SYSTEM.

SATURDAY AND SATURDAY NIGHT: WITH A INCREASING PRESSURE GRADIENT
WINDS SHOULD GRADUALLY INCREASE THROUGHOUT THE DAY. FORTUNATELY
WITH PRECIPITATION AND A STABLE ENVIRONMENT IT DOES NOT APPEAR
FAVORABLE FOR MIXING. SUSTAINED WINDS FROM 15-20 MPH WITH GUSTS UP
TO 30 MPH ARE POSSIBLE. WINDS JUST OFF THE SURFACE AT ABOUT
900-925 MB LOOK TO BE AROUND 50 MPH SO EVEN ISOLATED HIGHER GUSTS
CAN NOT BE RULED OUT. WINDS OFFSHORE MAY STRENGTHEN SOME SATURDAY
NIGHT (SEE MARINE).

SUNDAY: THE LOW PRESSURE WILL START TO MOVE AWAY REDUCING THE
PRESSURE GRADIENT. THE 900 MB WINDS SHOULD RELAX. HOWEVER A
STEEPER LAPSE RATE WILL BE PRESENT ALLOWING FOR MIXING. STILL
EXPECTING WINDS FROM 15-20 MPH WITH GUSTS TO 30 MPH.

WINDS WILL DEPEND ON THE ACTUAL EVOLUTION OF THIS SYSTEM(S).
STRONGER LOW MEANS A BIGGER PRESSURE GRADIENT AND STRONGER WINDS.
THE FORECASTED WINDS REFLECT A COMPROMISE BETWEEN THE STRONGER 00Z
ECMWF FROM THIS EVENING AND THE MORE STRUNG OUT AND WEAKER 12Z
GFS.

PRECIPITATION TYPE

THIS WILL HIGHLY DEPENDENT ON THE OVERALL MAKEUP OF THIS STORM.
OPTION ONE PRESENTED IN THE OVERVIEW SECTION WOULD MEAN RAIN
SHOWERS TO SCATTERED FLURRIES/SPRINKLES AS THE COLD AIR MOVES IN.
OPTION TWO WITH MORE INTERACTION BETWEEN THE LOWS IS MORE
INTERESTING. A LOW PRESSURE SYSTEM ORGANIZING MORE TO OUR SOUTH
WOULD DRAW MORE WARM AIR NORTHEAST (00Z ECMWF) AND KEEP THINGS ALL
RAIN TILL PERHAPS WRAP-AROUND STUFF SATURDAY NIGHT. IF THE LOW
PRESSURE INTERACTIONS TAKE PLACE OFF OUR COASTLINE THEN LESS WARM
AIR WOULD BE PULLED IN AND DYNAMIC COOLING MAY REALLY KEEP
TEMPERATURES DOWN SATURDAY AND ALLOW FOR CAA CHANGING RAIN TO SNOW
NW OF PHL SATURDAY AFTERNOON AS MID-LEVEL TEMPERATURES COOL BELOW
0C AT 925 AND 850 MB (06Z GFS). AN INVERTED TROUGH FEATURE MAY
DEVELOP AS WELL WHICH COULD LINGER STEADIER PRECIPITATION INTO
SATURDAY NIGHT AS WELL, USUALLY HARD TO PIN THESE DOWN. IN THE
UNLIKELY EVENT A SUSTAINED PERIOD OF SNOW WERE TO OCCUR RATIOS
WOULD BE 5:1 IF NOT LOWER DUE TO VERY WARM GROUND TEMPERATURES AND
SURFACE TEMPERATURES ABOVE FREEZING.

RIGHT NOW OPTION ONE APPEARS TO BE GAINING MORE TRACTION AND THAT
IS THE DIRECTION IN WHICH THIS FORECAST WILL GO, FOR BETTER OR
WORSE. THIS WOULD MINIMIZE SNOW CHANCES.

BOTTOM LINE
- STRONG WINDS ARE EXPECTED SATURDAY AND SATURDAY NIGHT WITH SOME
PERIODS OF COLD RAIN WITH THE THREAT OF VERY LIGHT MIXED
PRECIPITATION SATURDAY NIGHT.

- OF NOTE WHEN COMPARED TO THE LATE OCTOBER SNOWFALL IN 2011,
THIS SYNOPTIC SET-UP HAS CONSIDERABLE DIFFERENCES. THAT EVENT HAD
A CONSIDERABLE AMOUNT OF COLD AND DRY AIR ENTRAINED FROM A HIGH
PRESSURE SYSTEM WHICH ALLOWED FOR DYNAMICAL AND EVAPORATIONAL
COOLING. THIS SET-UP IS NOT EXPECTED TO HAVE EITHER OF THESE ATTM.

MONDAY AND TUESDAY: COOLER AND DRY WITH NORTHWEST FLOW GIVING WAY
TO SOUTHWESTERLY FLOW AS THE NEXT HIGH PRESSURE MOVES THROUGH. DID
UNDERCUT MEX AND OTHER STATISTICAL GUIDANCE DUE TO THE NORTHWEST
FLOW FOR MONDAY. ON TUESDAY WITH A SOUTHWESTERLY DID GO ABOVE THE
MODEL CONSENSUS ON TEMPERATURES.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

VFR CONDITIONS ARE EXPECTED THROUGH MUCH OF THE NIGHT WITH SOME
MVFR VISIBILITY RESTRICTIONS POSSIBLE TOWARD DAYBREAK. THE
POTENTIAL VISIBILITY RESTRICTIONS ARE FORECAST TO LAST UNTIL ABOUT
1300Z OR 1400Z, THEN VFR CONDITIONS ARE ANTICIPATED THROUGH THE
REMAINDER OF THE TAF PERIOD.

A BAND OF LIGHT RAIN SHOWERS IS EXPECTED TO WORK ITS WAY SLOWLY
ACROSS OUR REGION FROM WEST TO EAST FROM LATE TONIGHT THROUGH THE
DAY ON WEDNESDAY. THE PRECIPITATION SHOULD NOT BE HEAVY ENOUGH TO
HAVE A GREAT DEAL OF IMPACT ON CEILINGS AND VISIBILITY VALUES.

A LIGHT WIND OVERNIGHT MAY FAVOR THE SOUTH OR SOUTHWEST IN SPOTS.
THE WIND SHOULD START FROM THE SOUTHWEST ON WEDNESDAY MORNING
AROUND 4 TO 8 KNOTS. A COLD FRONT IS EXPECTED TO MOVE ACROSS OUR
REGION FROM THE WEST ON WEDNESDAY MORNING WITH THE WIND DIRECTION
VEERING TOWARD THE WEST.

OUTLOOK...
WEDNESDAY NIGHT THROUGH FRIDAY NIGHT: VFR WITH WINDS UNDER 10
KNOTS.

SATURDAY: MAINLY MVFR CONDITIONS LIKELY THROUGHOUT MOST OF THE
DAY WITH CLOUDS AND RAIN, OCCASIONAL IMPROVEMENT TO MVFR CAN NOT
BE RULED OUT. NORTHWEST WIND INCREASING FROM 10 TO 20 KNOTS IN THE
AFTERNOON WITH HIGHER GUSTS UP TO 30 KNOTS.

SATURDAY NIGHT: MAINLY VFR CONDITIONS WITH SOME MVFR CONDITIONS
IN LIGHT RAIN SHOWERS, POSSIBLY MIXED WITH NON ACCUMULATING SNOW
FLURRIES. NORTHWEST WINDS 10-20 KNOTS WITH GUSTS UP TO 25 KNOTS.

SUNDAY: VFR. NORTHWEST WINDS 15-25 KNOTS WITH GUSTS UP TO 30
KNOTS.

&&

.MARINE...
WE WILL MAINTAIN THE SMALL CRAFT ADVISORY FOR OUR OCEAN WATERS
FROM MIDNIGHT UNTIL 200 PM ON WEDNESDAY. CONDITIONS WILL BE
MARGINAL. THE STEADY SOUTH TO SOUTHWEST FLOW MAY BUILD SEAS NEAR 5
FEET ON OUR OUTER WATERS. OCCASIONAL WIND GUSTS AROUND 25 KNOTS
ARE ANTICIPATED.

CONDITIONS ARE EXPECTED TO REMAIN BELOW THE SMALL CRAFT ADVISORY
CRITERIA ON DELAWARE BAY.

OUTLOOK...
WEDNESDAY NIGHT THROUGH FRIDAY NIGHT: SUB SCA SEAS AND WINDS WITH
BUILDING SEAS AND INCREASING WINDS LATE FRIDAY AND FRIDAY NIGHT.

SATURDAY THROUGH SUNDAY: SCA WINDS LIKELY DEVELOPING EARLY
SATURDAY WITH THE DEVELOPMENT OF LOW PRESSURE OFF THE COAST. GALE
WIND GUSTS POSSIBLE LATE SATURDAY AFTERNOON THROUGH SUNDAY.
LINGERING SCA GUSTS POSSIBLE SUNDAY NIGHT. SEAS ABOVE SCA
CRITERIA.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT WEDNESDAY FOR ANZ450>455.

&&

$$

SYNOPSIS...GAINES
NEAR TERM...IOVINO
SHORT TERM...IOVINO
LONG TERM...GAINES
AVIATION...GAINES/IOVINO
MARINE...GAINES/IOVINO






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