Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 221330
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
830 AM EST THU JAN 22 2015

.SYNOPSIS...
WEAK LOW PRESSURE IN NORTHEASTERN PENNSYLVANIA WILL MERGE WITH A
SEAWARD DEVELOPING LOW PRESSURE OFF THE MID ATLANTIC COAST. HIGH
PRESSURE IN THE CENTRAL PLAINS WILL SLIDE INTO OUR REGION THIS
AFTERNOON AND TONIGHT. THIS HIGH PRESSURE WILL MOVE THROUGH ON
FRIDAY BEFORE GIVING WAY TO A LOW PRESSURE SYSTEM TRACKING UP THE
COAST ON SATURDAY. ON SUNDAY A LOW PRESSURE SYSTEM WILL TRACK
ACROSS THE GREAT LAKES AND INTO OUR REGION ON MONDAY. THIS LOW
PRESSURE WILL DEPART THE REGION BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE WINTER WEATHER ADVISORY WAS ALLOWED TO EXPIRE AT 800 AM. WE
HAVE ISSUED A SPECIAL WEATHER STATEMENT TO COVER ANY RESIDUAL ICY
SPOTS THROUGH 1000 AM.

THERE IS A BAND OF WHAT APPEARS TO BE SNOW SHOWERS MOVING EAST
ACROSS THE DELMARVA AND FAR SOUTHERN NEW JERSEY. THOSE SNOW
SHOWERS MAY BE MIXED WITH FREEZING RAIN OR SLEET AND SHOULD BE OUT
TO SEA BY 16Z. THIS BAND OF SHOWERS AND THE FLURRIES ELSEWHERE
APPEAR TO ASSOCIATED WITH ONE LAST SHORT WAVE MOVING EAST ACROSS
PA THIS MORNING. ONCE THAT SHORT WAVE PASSES BY TO OUR EAST THE
WEAK SFC LOW IN CENTRAL PA SHOULD FILL AND NW FLOW WILL SLOWLY
STRENGTHEN AND THE LOW OVERCAST WILL BEGIN TO BREAK.

THIS AFTERNOON IS STILL CONSIDERABLY CLOUDY BUT IMPROVED OVER THE
CONDITIONS OF THIS MORNING WITH BRIGHTENING SKIES.

THE TEMP FCST IS A 50 50 BLEND OF THE 00Z/22 NAM/GFS MOS AND THEN
THAT WAS BLENDED WARMER BY 2 DEGREES BECAUSE OF THE WARMER ECMWF!
THIS WOULD RESULT IN MAX TEMPS SLIGHTLY WARMER THAN NORMAL.

IF WE END UP WITH MORE SUNSHINE THAN YDY...WE COULD SEE THE
REGION FROM PHILADELPHIA NORTHWARD...WHERE THERE WASNT MUCH
SNOWFALL LATE YESTERDAY...RUNNING WARMER BY A DEGREE OR 2 ABOVE
OUR 330 AM DETERMINISTIC FCST.

WINDS AND DEW POINTS WERE A 50 50 BLEND OF THE 00Z/22 NCEP MOS
GUIDANCE.

I DONT SEE MUCH GUSTINESS TODAY...NW GUST MAX ABOUT 15 MPH.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
TSECTIONS AND LAPSE RATES SUGGEST THAT CLEARING WILL BE FAIRLY
QUICK LATE THIS AFTERNOON/EVENING.

SO A MOSTLY CLEAR NIGHT IS EXPECTED. A LIGHT NW WIND.

PATCHY FOG IS NOT IN THE FCST TONIGHT BUT MAYBE IT WILL BE FROSTY
DUE TO STILL SOMEWHAT ELEVATED DEW POINTS.

TEMPS/DEWS/WINDS ARE A 50 50 BLEND OF THE 00Z/22 NAM/GFS MOS
GUIDANCE WITH SOME COOLING OF THOSE BLENDED TEMPS BY 2 DEGREES OR
SO IN THE PINE BARRENS OF SNJ AND ALSO IN THE COOLER RADIATORS OF
BUCKS AND MONTGOMERY COUNTIES IN PA WHERE A LITTLE SNOW
ACCUMULATED. ITS DEBATABLE HOW MUCH OF THAT SNOW WILL REMAIN BY
NIGHTFALL. THESE FORECAST LOWS ARE NEAR NORMAL FOR THE DATE.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
FRIDAY: HIGH PRESSURE WILL BUILD BACK INTO THE REGION RESULTING
IN A MOSTLY SUNNY DAY. DID NOT GO AS WARM AS THE NEW MAV AND MET
RUNS FOR TEMPERATURES BUT THIS COULD BE POSSIBLE GIVEN AMPLE
SUNSHINE.

FRIDAY NIGHT THROUGH SATURDAY NIGHT: LOW PRESSURE WILL TRACK UP
THE EAST COAST. THE SPREAD IN THE OPERATIONAL MODEL RUNS AND THE
VARIOUS ENSEMBLES HAVE DECREASED. THIS INCLUDES SOME OF THE
WESTERN ECMWF ENSEMBLES, THROUGH EXAMINATION OF THE MEAN. THE 18Z
GEFS ALSO APPEAR TO HAVE A TIGHTER SPREAD COMPARED TO PREVIOUS
RUNS. THE NAM AND GFS REMAIN FURTHER OFFSHORE AND LESS DEVELOPED
WITH THE ECMWF TRENDING IN THIS DIRECTION AS WELL. HOWEVER THE CMC
AND UKMET CONTINUE TO BE CLOSER TO THE COAST WITH HIGHER QPF. THE
OVERALL TREND OVERNIGHT WAS TO SHOW A MORE DISORGANIZED LOW
PRESSURE SYSTEM.

IN TERMS OF WEATHER, SNOW OR THE CHANCES FOR MIXED PRECIPITATION
WILL BEGIN TO INCREASE FROM SOUTH TO NORTH FRIDAY NIGHT WITH
OVERRUNNING WAA. MODERATE PRECIPITATION WILL LIKELY OCCUR WITHIN
THIS PRECIPITATION SHIELD WITH THE BULK OF SNOWFALL ACCUMULATIONS.
THERMAL PROFILES SUGGEST THAT THE DELMARVA AND COASTAL NJ WILL
CHANGE TO RAIN BY SATURDAY MORNING, WITH SLEET MIXED AS WELL. THIS
IS DUE TO THE POTENTIAL OF MID-LEVEL WARMING IS GREATER THAN IN
THE AIR TEMPERATURE CLOSER TO THE SURFACE. LIGHTER PRECIPITATION
WILL BE NOTED NW OF PHL FURTHER FROM THE LOW. AFTER THIS PUSH OF
PRECIPITATION A DRY SLOT OR LINGERING LIGHT RAIN OR A RAIN/SNOW
MIX ( NW OF PHL) SHOULD CONTINUE INTO THE AFTERNOON, SURFACE
WARMING IS GREATER THAN MID-LEVEL WARMING AT THIS POINT. A CCB MAY
STILL FORM ON THE BACKEND OF THE LOW PRESSURE SYSTEM WITH A PERIOD
OF SNOW OR RAIN CHANGING TO SNOW. THE MORE DISORGANIZED TRENDS
HAVE DECREASED THE CHANCES OF THIS TO OCCUR. OUR QPF FORECAST TOOK
ELEMENTS OF THE WPC, SREF AND THE ECMWF. ALSO KEEPING IN MIND THE
MORE BULLISH QPF SOLUTIONS OF THE UKMET AND CMC. A ZONE FROM THE
LEHIGH VALLEY TO INTERSTATE 295 HAVE THE HIGHEST CHANCES OF SEEING
SNOW TOTALS FROM 3-4 INCHES, WITH LOWER AMOUNTS SURROUNDING THIS
ZONE. THIS IS DUE TO A QUICK CHANGEOVER SE AND LESS QPF NW. FOR
TEMPERATURES STAYED CLOSER TO THE MODELED TWO METER TEMPERATURES
WHICH RESPECTIVE MODELS HAD PRECIPITATION IN THE FORECAST.

SUNDAY: A TEMPORARY BREAK BETWEEN SYSTEMS WITH A MIX OF CLOUDS
AND SUN. TEMPERATURES COULD BE COOLER THAN ENSEMBLES/MEX GUIDANCE
DUE TO SNOW COVER.

SUNDAY NIGHT THROUGH MONDAY NIGHT: ANOTHER SYSTEM DIVES SOUTHEAST
FROM THE GREAT LAKES REACHING OUR REGION BY MONDAY MORNING. THIS
LOOKS TO BE ANOTHER CLIPPER TYPE SYSTEM WHICH THEN TRANSFERS IT`S
ENERGY TO A COASTAL LOW. THERE IS A HIGHER DEGREE OF SPREAD
COMPARED TO THE SATURDAY SYSTEM IN THE ENSEMBLES WITH THIS FEATURE
IN THE OVERALL TRACK AND HOW MUCH IT CAN STRENGTHEN ONCE IT
REACHES THE EAST COAST. FOR NOW CARRYING A CHANCE OF SNOW ACROSS
THE REGION WITH SOME MIX ACROSS THE COAST CHANGING TO SNOW FOR
SUNDAY NIGHT THROUGH MONDAY NIGHT. THOUGHT THE 00Z GFS WAS TO
STRONG WITH THIS FEATURE ALLOWING FOR EXCESSIVE WAA, OUR
PRECIPITATION TYPE FORECAST WAS CONSIDERABLY MORE WINTRY IN LINE
WITH THE ECMWF.

TUESDAY AND WEDNESDAY: INDICATIONS CONTINUE TO A FAIRLY POTENT
ARCTIC AIR MASS COMING IN BEHIND THE DEPARTING SYSTEM. SEVERAL GEFS
MEMBERS ARE QUITE POTENT DELIVERING AN AIR MASS WITH 850 MB TEMPS
AROUND -20C AND MOST OPERATIONAL MODELS ARE AT LEAST -10C.
UNDERCUT ENSEMBLE GUIDANCE. A FRESH SNOW COVER COULD ALSO MAKE THIS
PERIOD RATHER CHILLY. SKIES WILL BE MOSTLY CLEAR WITH A NORTHWEST
FLOW.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

THROUGH 16Z...CIGS GENERALLY 500 TO 1500 FEET THIS MORNING WITH
AREAS OF LIGHT SNOW REDUCING VSBY TO 3 TO 5 MI. LIGHT NORTHWEST
WIND.

AFTER 16Z TODAY...CIGS IMPROVING TO 1500-2500 AND THEN AOA 3000
FT BY 21Z AS NW WINDS SLOWLY INCREASE WITH A FEW GUSTS NEAR 15 KT
THIS AFTERNOON.

TONIGHT...VFR CLEAR. LIGHT NW WIND. CONFIDENCE ABOVE AVERAGE.
SMALL CHC SOME PATCHY FOG LATE IN THE COUNTRYSIDE.

OUTLOOK...

FRIDAY: VFR, INCREASING CLOUDS

FRIDAY NIGHT THROUGH SATURDAY NIGHT: IFR/LIFR CEILINGS AND
VISIBILITIES IN SNOW AND RAIN. LOWEST CEILINGS FROM 08-14Z
SATURDAY, ACCUMULATING SNOW AT PHL EXPECTED. MORE RAIN SOUTHEAST
OF PHL AND SNOW NORTHWEST OF PHL. NORTHWEST GUSTS UP TO 20 KNOTS
SATURDAY AFTERNOON AND NIGHT.

SUNDAY: VFR.

SUNDAY NIGHT AND MONDAY: INCREASING CLOUDS, POTENTIAL LOWER
CEILINGS DUE TO SNOW LATE SUNDAY NIGHT AND MONDAY.

&&

.MARINE...
LIGHT W-NW WIND INCREASING THIS AFTERNOON AND TONIGHT WITH NW
GUSTS TO 20 KT. SMALL CHANCE OF BRIEF GUSTS 25 KT THIS EVENING
VCNTY DELAWARE BAY. NO SCA ATTM...THROUGH DAYBREAK FRIDAY.

WAVE HEIGHTS ON OUR OCEAN WATERS SHOULD BE 2 TO 4 FEET THROUGH
DAYBREAK FRIDAY.

OUTLOOK...
FRIDAY AND FRIDAY NIGHT: SUB SCA SEAS AND WINDS INCREASING FRIDAY
NIGHT.

SATURDAY AND SATURDAY NIGHT: SCA SEAS AND GUSTS BY AFTERNOON.
WINDS FROM THE EAST SHIFTING TO NORTHWEST BY SATURDAY NIGHT. SOME
GALE FORCE GUSTS POSSIBLE SATURDAY NIGHT.

SUNDAY AND SUNDAY NIGHT: SEAS AND WIND GUSTS DECREASING BELOW SCA
CRITERIA BY SUNDAY AFTERNOON.

MONDAY: AN SCA MAY BE NEEDED AS AN ALBERTA CLIPPER REDEVELOPS OFF
THE MID ATLANTIC COAST.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$

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





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