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Area Forecast Discussion
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000
FXUS61 KPHI 252340
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
640 PM EST TUE NOV 25 2014

.SYNOPSIS...
LOW PRESSURE NEAR FLORIDA THIS EVENING WILL STRENGTHEN AS IT PASSES 
NEAR THE MID ATLANTIC COAST WEDNESDAY, BEFORE RACING TO THE NORTHEAST
WEDNESDAY NIGHT. HIGH PRESSURE IS FORECAST TO BUILD ACROSS THE
EAST COAST FRIDAY INTO EARLY SATURDAY, BEFORE SQUEEZING TO THE
SOUTH SATURDAY NIGHT. A COLD FRONT IS EXPECTED TO SAG DOWN ACROSS
THE AREA SUNDAY NIGHT, BEFORE SLOWLY MOVING THROUGH THE AREA
MONDAY INTO MONDAY NIGHT.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
NO BIG CHANGES WITH THIS ESTF UPDATE. USED LATEST RAP RUNS TO MAKE
SOME MINOR POP ADJUSTMENTS OVERNIGHT. WHERE SKIES HAVE THINNED FAR
NORTHWEST, TEMPS HAVE DROPPED QUICKLY. BOTH THE 18Z GFS AND WRF-
NMMB HAVE CONTINUED THE WARMER TREND. WRF-NMMB IS NOW HALF SNOW AT
PHL AND IT WAS ALL SNOW WITH ITS 12Z RUN WHILE THE GFS IS MOSTLY
RAIN AT PHL EXCEPT FOR ONE DYNAMICALLY COOLED 3 HR PERIOD DURING
THE AFTERNOON. SOME OF THAT WARMTH HAS WAFTED AROUND 700MB
TEMPERATURES ABOVE FREEZING INTO THE I95 CORRIDOR AND SLEET IS
SHOWING UP AS A PTYPE. GOING TO WAIT AND SEE HOW THE MODELS
925MB/850MB FORECASTS VERIFY OFF THE 12Z SOUNDINGS, SO ONLY A
SLIGHT SHAVING OF SNOW TOTALS WAS DONE SOUTHEAST OF I95.


TONIGHT...THICKENING AND LOWERING CLOUDS AS DYNAMICS WITH THE
FLORIDA LOW AND GULF COAST SHORT WAVE FLOOD NORTHWARD. RAIN
DEVELOPS RAPIDLY FROM SOUTH SOUTHWEST TO NORTH NORTHEAST AFTER
MIDNIGHT AS LOW PRESSURE HEADS NEWD FOR THE NC COAST. NORTHERN
FRINGE REACHING KRDG/KABE AT 11Z MAY BEGIN AS RAIN/SNOW MIX PER
MARGINAL WARM BOUNDARY LAYER TEMPS (A WALL OF DEEP RH MOVING
NORTHWARD IN OUR CWA AFTER MIDNIGHT).

50 50 BLENDED 12Z/25 NCEP MOS GUIDANCE.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
UPDATE TO THIS SECTION COMING BY 330 PM.

**HIGH VISIBILITY HIGH IMPACT SNOW EVENT FOR ELEVATIONS OF E PA
 AND NW NJ 9A-9P AND LIKELY A DEVELOPING IMPACT EVENT TO NEAR SEA
 LEVEL JUST NW OF I-95 WEDNESDAY AFTERNOON/EVENING**

THIS FORECAST WAS A 50 50 BLEND OF THE 12Z/25 WARMER GFS AND COLDER
ECMWF PARTIAL THICKNESSES AND THEN ADJUSTING THE WET BULBING
12Z/25 BLENDED MOS TEMPS COLDER, ESPECIALLY WITH THE COLUMN ALL
SNOW DOWN TO 5000 FT AND ICE NUCLEI SEEDED FOR CRYSTALS BY CIRRUS. 

LOW PRESSURE SYSTEM HAS BEEN TRENDING FASTER ONSET/DEPARTURE
SINCE FIRST DISCUSSED IN DETAILS THIS PAST WEEKEND.

SNOW GRIDS ARE POSTED. 

WE SAW THE WARMER 18Z NAM (700MB ABOVE ZERO DOWN HERE NEAR PHL).
THE SNOW AMOUNTS NEAR I-95 FROM CECIL COUNTY MARYLAND THROUGH 
WILMINGTON DELAWARE AND THEN NORTHEAST THROUGH PHILADELPHIA UP
TO NEW BRUNSWICK ARE HIGHLY UNCERTAIN. THE ADVISORY AREA SNOW
AMOUNTS ARE SHAKY AND WE MAY NOT MUCH MORE UNTIL NOON TOMORROW?
THE ADVISORY MAY NEED TO BE EXPANDED SOUTHWEST INTO NE MD IN
FUTURE FORECASTS. 

POCKETS OF POWER OUTAGES A CONCERN...ESPECIALLY JUST NORTHWEST OF
INTERSTATE 95.

SUGGEST TRAVEL INTO EASTERN PENNSYLVANIA AND NORTHWEST NEW JERSEY
BE COMPLETED NO LATER THAN 7 AM WEDNESDAY, OR WAIT TIL AFTER 7 PM
WEDNESDAY NIGHT (IE...AFTER ROADS ARE CLEANED UP/CLEARED OF SLUSHY
SNOW). ITS THAT 12 HOUR WINDOW DURING THE DAY WEDNESDAY THAT IS
GOING TO BECOME A SIGNIFICANT TRAVEL PROBLEM, ESPECIALLY THE HILLY
AREAS.

ITS UNUSUAL TO FORECAST HEAVY WET SNOW IN A 1000-500MB 543-546 THICKNESS
WITHOUT A BIG (1030MB) SURFACE HIGH TO THE NORTH BUT THIS IS A SITUATION
THAT I THINK HEAVY SNOW WILL OCCUR, ESPECIALLY ELEVATIONS FOR REASONS
BELOW. THERMAL PROFILES AND PCPN MICROPHYSICS WITH CIRRUS SEEDING MARGINAL
-2 TO -8C BELOW 15,000 FEET!! THIS IS ANOTHER TEST OF THAT PRECIPITATION
MICROPHYSICS WHICH HAS WORKED SO WELL IN THE PAST.

AN INTENSIFYING 500MB 12HR 180 M HFC MOVING NEWD COMBINES WITH
ISALLOBARIC GRADIENT TO PULL 0-6KM 1C OR LESS WBZ AIR PROGRESSIVELY
SEWD TO NEAR I95 BY 18Z AND TO THE ATLANTIC COAST BY 00Z/27
(WEDNESDAY EVENING-TOO LATE FOR ANY SNOW SNJ AND DE COASTS).
ELEVATIONS CHANGE TO SNOW FIRST FROM NORTHWEST TO SOUTHEAST 
WEDNESDAY MORNING.

PIVA AND COMMA HEAD SUGGEST SOME BANDING POTENTIAL VCNTY KRDG TO
KMPO DURING THE DAY. ALSO SUPPORT FROM CSI PRODUCT OF THE NAM BUT
AGAIN ITS THE NAM. THE MAX UVM RIGHT NOW IS TENDING TO SHOW UP BELOW
THE IDEAL DENDRITIC GROWTH ZONE IN THE MULTI MODEL PROFILES BUT
THAT CAN CHANGE.

A RECORD DAILY SNOWFALL FOR ALLENTOWN PA IS LIKELY TO OCCUR (A
VULNERABLE RECORD).

SNOW WATER RATIOS PER INTERNAL COLLABORATION 6 TO 1 I-95 MAYBE
8 TO 1 KRDG TO KABE AND 10 OR 12 TO 1 FOR THE POCONOS.

SMALL CHANCE OF MINOR TIDAL FLOODING ALONG THE DE COAST FOR
TOMORROW MORNINGS HIGH TIDE.

SMALL CHANCE WE'LL NEED A WIND ADVISORY FOR THE DELAWARE COAST
TOMORROW MORNING.  

SNOW/PRECIPITATION ENDS FROM SW TO NE WEDNESDAY EVENING WITH SOME
REMAINING BANDING SNOW OVER NE PA AND NW NJ.

FLURRIES MAY OCCUR LATE AT NIGHT?

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
ON THANKSGIVING, THERE WILL REMAIN A CHANCE FOR ISOLATED SHOWERS FOR 
PORTIONS OF THE AREA, ALTHOUGH WE EXPECT MOST AREAS TO REMAIN DRY. 
THERE COULD REMAIN SOME SNOW SHOWERS IN THE NORTHERLY FLOW ACROSS 
OUR NORTHERN AREAS, AND AS A SHORT WAVE ROUNDS THE BASE OF THE 
TROUGH ALOFT, IT MAY HELP CREATE AN AREA OF SHOWERS ACROSS THE 
SOUTHERN PORTIONS OF THE AREA AS WELL. MOST AREAS SHOULD STAY
PRECIP FREE, BUT IF IT DOES SNOW ACROSS THE NORTHERN ELEVATIONS, A
LIGHT ACCUMULATION COULD OCCUR WITH SOME SHOWERS. BY THURSDAY
NIGHT, ANY PRECIPITATION IS EXPECTED TO END AS WE BEGIN TO LOSE
GOOD MOISTURE ALOFT.

FRIDAY INTO EARLY SATURDAY, HIGH PRESSURE BEGINS TO BUILD ACROSS THE 
EAST COAST, WHICH IS EXPECTED TO KEEP THE WEATHER MOSTLY 
PRECIPITATION FREE. THE MODELS DO PUSH A WEAK SHORT WAVE/VORTICITY 
IMPULSE ACROSS THE AREA FRIDAY NIGHT, WITH THE GFS SHOWING MORE 
MOISTURE TO WORK WITH THAN THE ECMWF. FOR NOW WE WILL KEEP THE 
WEATHER DRY UNTIL WE GET BETTER COLLABORATION BETWEEN THE TWO.

THE HIGH PRESSURE PUSHES TO OUR SOUTH LATER SATURDAY INTO EARLY 
SUNDAY, BEFORE A FRONTAL BOUNDARY APPROACHES THE AREA SUNDAY NIGHT 
INTO MONDAY. MODELS ARE HINTING AT A SLIGHT CHANCE OF SHOWERS 
SATURDAY NIGHT INTO SUNDAY AS A COUPLE OF WEAK SHORT WAVE/VORTICITY 
IMPULSES SLIDE ACROSS THE AREA. HOWEVER, THE GREATER THREAT IS 
EXPECTED TO BE SUNDAY NIGHT INTO MONDAY NIGHT AS THE FRONTAL
BOUNDARY SAGS ACROSS THE AREA. MODELS INDICATE THAT SOME MOISTURE
IS LOST AS THE FRONT SAGS ACROSS THE AREA, BUT THERE WILL REMAIN A
CHANCE IN THE FORECAST FOR NOW.

AS HIGH PRESSURE BUILDS BACK ACROSS THE NORTHEAST ON TUESDAY, DRY
WEATHER SHOULD RETURN TO THE AREA THROUGH TUESDAY.

AFTER BELOW NORMAL TEMPERATURES FOR THE FIRST HALF OF THE
EXTENDED THROUGH SATURDAY, A WARMING TREND IS EXPECTED FOR THE
LATTER HALF OF OF THE WEEKEND INTO EARLY NEXT WEEK WITH
TEMPERATURES RETURNING ABOVE NORMAL.

&&

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

HIGH IMPACT IFR CONDITIONS PREDICTED FOR WEDNESDAY.

FOR TONIGHT PRIMARILY VFR (HIGH LEVEL AND THEN MID LEVEL CLOUDS),
POSSIBLY BECOMING MVFR TOWARD MORNING AS PCPN (MAINLY RAIN) MOVES
INTO THE AREA. WIND DIRECTION FORECAST IS MORE FOR THE OVERNIGHT.

WEDNESDAY, KABE AND KRDG IFR CONDITIONS WITH SNOW AS THE
PREDOMINATE PTYPE BY THE MIDDLE OF THE MORNING. ACCUMULATIONS ON 
RUNWAYS LIKELY. SOME IMPROVEMENT LATE. NORTH WINDS WILL AVERAGE
AROUND 10 TO 15 KNOTS. KPHL/I95 CORRIDOR TERMINALS. MVFR
CONDITIONS IN RAIN DURING THE MORNING LOWERING TO IFR LATE MORNING
AS SNOW STARTS TO MIX IN AND PROBABLY BECOMES THE PREDOMINANT
PTYPE. SOME SLUSHY ACCUMS ON RUNWAYS POSSIBLE. WE ADDED THE
POSSIBILITY OF SLEET AS A PTYPE. MVFR IMPROVEMENT LATE. NORTHEAST
WINDS WILL AVERAGE 10 TO 20 KNOTS WITH PEAK GUSTS CLOSE TO 30
KNOTS. KMIV AND KACY AS WELL AS SHORE POINT AIRPORTS, IFR
CONDITIONS DUE TO PREDOMINATELY MODERATE RAIN. SOME SNOW MIGHT MIX
IN DURING THE AFTERNOON. NORTHEAST WINDS WILL AVERAGE 12 TO 18
KNOTS WITH PEAK GUSTS ALSO CLOSE TO 30 KNOTS, POSSIBLY HIGHER AT
COASTAL AIRPORTS.
 
OUTLOOK...
WEDNESDAY NIGHT...BECOMING VFR WITH DIMINISHING WINDS.

THURSDAY-THURSDAY NIGHT...MOSTLY VFR. ISOLATED RAIN OR SNOW SHOWERS
POSSIBLE DURING THE DAY WHICH MAY TEMPORARILY LOWER CONDITIONS.

FRIDAY-SUNDAY...MOSTLY VFR. WIND GUSTS 15-20 KNOTS EACH DAY; NW 
FRIDAY, SW SATURDAY & SUNDAY.

&&

.MARINE...
EARLY TOMORROW MORNING, GALE CONDITIONS ARE FORECAST FOR THE
LOWER DELAWARE BAY AND THE ATLANTIC COASTAL WATERS...ESPECIALLY
SOUTHERN NJ AND THE DE COASTAL WATERS. 

WED...A FULL BLOWN GALE WARNING IS IN EFFECT FOR THE COASTAL WATERS
AND LOWER DELAWARE BAY PER AN INTENSIFYING STORM MOVING NEWD FROM
THE NC COAST. SCA CONDITIONS EXPECTED ON THE UPPER DELAWARE BAY
WITH A POSSIBLE NEED FOR AN UPGRADE TO A SHORT FUSE GALE WARNING.

THE 06Z, 12 AND 18Z NAM ARE ADVERTISING A PERIOD OF STORM FORCE
WINDS VCNTY 44009 AROUND MIDDAY WEDNESDAY (NEAR 50 KT). WE WILL
NOT KNOW FOR SURE SINCE NO 44009 WIND DATA.

WED NIGHT...GALE CONDITIONS WILL CONTINUE EARLY, THEN SEAS AND WIND
WILL DECREASE AND AND SCA WILL BE LIKELY NEEDED AS THE STORM MOVES
NORTHEAST OF CAPE COD.

OUTLOOK...
THURSDAY-THURSDAY NIGHT...WINDS ARE EXPECTED TO BE BELOW SMALL CRAFT 
ADVISORY LEVELS, BUT SEAS MAY REMAIN ELEVATED INTO THURSDAY NIGHT.

FRIDAY-FRIDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED 
AS HIGH PRESSURE BUILDS OVER THE AREA.

SATURDAY-SUNDAY...NEAR SMALL CRAFT ADVISORY CONDITIONS POSSIBLE AS 
HIGH PRESSURE PUSHES TO OUR SOUTH AND COLD FRONT APPROACHES LATE ON 
SUNDAY NIGHT.

&&

.CLIMATE...
REGARDING THE MIDWEEK COASTAL STORM BRINGING SNOW TO A LARGE
PORTION OF OUR REGION, WE HAVE INCLUDED DAILY SNOWFALL RECORDS
BELOW FOR OUR FOUR PRIMARY CLIMATE SITES THAT HAVE A LONG-STANDING
UNBROKEN PERIOD OF RECORD (POR) WITH RESPECT TO HISTORICAL
SNOWFALL DATA.



DAILY SNOWFALL RECORDS:

NOVEMBER 26TH:               NOVEMBER 27TH:       PERIOD OF RECORD:

ACY: TRACE 1977,1957,1955    1.2 INCHES 1978            1874

PHL: 6.0 INCHES 1898         6.9 INCHES 1949,1938       1872

ILG: 0.1 INCHES 1950         4.5 INCHES 1978            1894

ABE: 1.7 INCHES 1925         7.0 INCHES 1938            1922

OTHER COOPERATIVE SITE SHORTER HISTORICAL RECORD CAN BE FOUND AT
THE NWS MOUNT HOLLY WEBSITE UNDER NOW DATA.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER STORM WARNING FROM 7 AM TO 10 PM EST WEDNESDAY FOR 
     PAZ054-055-060>062-101-103-105.
     WINTER WEATHER ADVISORY FROM 9 AM TO 10 PM EST WEDNESDAY FOR 
     PAZ070-071-102-104-106.
NJ...WINTER STORM WARNING FROM 7 AM TO 10 PM EST WEDNESDAY FOR 
     NJZ001-007>010.
     WINTER WEATHER ADVISORY FROM 9 AM TO 10 PM EST WEDNESDAY FOR 
     NJZ012-015.
DE...NONE.
MD...NONE.
MARINE...GALE WARNING FROM 4 AM TO 10 PM EST WEDNESDAY FOR ANZ431-
     450>455.
     SMALL CRAFT ADVISORY FROM 4 AM TO 10 PM EST WEDNESDAY FOR 
     ANZ430.

&&

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






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