National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS61 KPHI 092129
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
429 PM EST MON DEC 9 2013

.SYNOPSIS...
LOW PRESSURE EAST OF LONG ISLAND IS MOVING NORTHEAST WHILE A NEW
AREA OF LOW PRESSURE FORMS IN NORTH CAROLINA TONIGHT. THAT NORTH
CAROLINA LOW ZIPS NORTHEAST OUT TO SEA TUESDAY AFTERNOON YANKING IN
COLDER AIR BEHIND IT TUESDAY NIGHT. HIGH PRESSURE WILL THEN BUILD
INTO THE REGION FROM THE WEST DURING MID AND LATE WEEK BEFORE
SHIFTING INTO THE WESTERN ATLANTIC SATURDAY. LOW PRESSURE AND A NEW
COLD FRONT ARE SLATED TO MOVE ACROSS THE MID ATLANTIC STATES LATE
SATURDAY. CANADIAN HIGH PRESSURE SHOULD FOLLOW...ARRIVING IN THE
NORTHEAST UNITED STATES EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
WE`LL BE IN A LULL MOST OF TONIGHT, BETWEEN YESTERDAY`S SNOW AND
WHAT`S TO COME TOMORROW. IMPACTS TONIGHT WILL BE ASSOCIATED WITH FOG
AND RESTRICTIVE VISIBILITIES AND SUB-FREEZING TEMPERATURES THAT
COULD REFREEZE WHAT`S CURRENTLY ON THE GROUND.

TEMPERATURES WILL FALL INTO THE LOWER 20S ACROSS THE NORTHWEST ZONES
AND INTO THE UPPER 20S ELSEWHERE.

PRECIPITATION WILL BE REENTERING THE PICTURE TOMORROW MORNING.
THINGS COULD START TO RAMP UP PRIOR TO 6AM. SOUNDINGS SUGGEST ALL
SNOW AT THE ONSET EXCEPT FOR OUR SOUTHERN COUNTIES WHERE SOME
FREEZING RAIN AND SLEET IS POSSIBLE. THE MORNING RUSH COULD BE
IMPACTED, ALTHOUGH IT APPEARS, AT LEAST AT THIS TIME, THAT WHEN YOU
GET NORTH OF DELMARVA, THE ONSET OF PRECIPITATION WILL COMMENCE
DURING THE SECOND HALF OF THE COMMUTE.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
WINTER STORM WARNINGS AND WINTER WEATHER ADVISORIES HAVE BEEN
ISSUED. ALTHOUGH BANDING PREDICTABILITY IS FAIRLY LOW, MODELS ARE
POINTING TO THE I95 CORRIDOR AT THIS TIME.

H8-H7 FORCING IS IN PLACE TOMORROW MORNING AS WELL OMEGA. DECENT
SNOW GROWTH IS FORECAST AND WE`RE UNDER THE RIGHT REAR OF THE H3
JET. THE FEELING IS...THERE WILL BE AT LEAST MODERATE SNOW FOR A FEW
HOURS THAT WILL COMPENSATE FOR A DAYTIME SNOWFALL WITH TEMPERATURES
NEAR FREEZING.

WE LIKE 3 TO 5 INCHES ACROSS THE I95 CORRIDOR AND THAT`S WHAT IS IN
THE WSW. OUR GRAPHICS ON THE WEB WILL DISPLAY 4 TO 6 INCHES, WITH 3
TO 5 NOT BEING AN OPTION. LESS AMOUNTS SHOULD FALL ACROSS THE FAR
NORTHWESTERN ZONES, THE FAR SOUTHERN ZONES AND RIGHT ALONG THE COAST.

THE GFS QPF IS ON THE HIGH SIDE OF THE SPECTRUM WHILE THE EURO IS ON
THE LOWER SIDE. WE`RE IN THE MIDDLE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
500MB: A BROAD TROUGH IN EASTERN UNITED STATES SHARPENS UP A BIT
THURSDAY AS SHORT WAVES MOVE THROUGH THE BASE OF THE TROUGH. RIDGING
FOLLOWS FRIDAY AND THEN WE WAIT TO SEE HOW THE MID WEEK CLOSED LOW
NEAR BAHA CALIFORNIA INTERACTS WITH THE NORTHERN STREAM FOR NEXT
WEEKEND. LOTS OF UNCERTAINTY IN THE MODELS FOR NEXT WEEKEND WHICH
INCLUDES TEMPS...PTYPE AND STORM TRACK. TROUGHING DEVELOPING IN
THE EASTERN USA MAKES IT PROBABLE THAT SOME SORT OF PRECIPITATION
SHOULD DEVELOP HERE NEXT WEEKEND.

TEMPERATURES: MUCH BELOW NORMAL COLD FOR PORTIONS OF THIS EXTENDED
PERIOD WITH CALENDAR DAY AVERAGE VALUES EXPECTED TO BE 10 DEGREES OR
MORE COLDER THAN NORMAL WEDNESDAY THROUGH FRIDAY AND POSSIBLY AGAIN
NEXT MONDAY WITH FRIDAYS TEMPERATURES POSSIBLY 15 DEGREES BELOW
NORMAL! THE MILDEST DAYS SHOULD BE SATURDAY AND OR SUNDAY.

FORECAST BASIS... TUE NIGHT-WED NIGHT IS A 50 50 BLEND OF THE 12Z/9
GFS/NAM MOS.  THURSDAY IS 100 PCT 12Z/9 GFS MOS AND THEN THU NIGHT-
NEXT MONDAY IS THE 1522Z/9 WPC EXTENDED GRIDS.  THIS DATA IS CHECKED
AGAINST THE 12Z/9 ECMWF...MODIFIED AND NOTED IN THE DAILIES WHEN
SIGNIFICANT. THE 09Z/9 SREF WAS CHECKED FOR POPS WITHIN ITS FORECAST
RANGE THE 12Z/9 GEFS 6HR POPS FOR .05 WERE CHECKED FOR THE EXTENDED
GRIDS THURSDAY-MONDAY.

THE DAILIES BELOW...

TUE NIGHT...CLEARING AND COLDER WITH FREEZE UP OF THE TUESDAY SNOW
EVENT. WINTRY LOOKING NIGHT-SCAPE. A BIT OF AN ADDED WIND CHILL
TOO!

WEDNESDAY AND THURSDAY...POTENTIAL FOR BURSTS OF SNOW SHOWERS
NEAR AND NORTH OF I80 IN NE PA AND NW NJ AS THE SOUTHERN EXTENT
OF WINDEX EVENTS ARE SUGGESTED BY THE GUIDANCE TO GRAZE THE NORTHERN
PORTION OF OUR FORECAST AREA. THE SHORT WAVES ARE SENDING IN BURSTS
OF COLDER AIR IN GENERAL WNW FLOW AND YOU COULD ARGUE THAT A SECONDARY
COLD FRONTAL PASSAGE CAN OCCUR WEDNESDAY NIGHT. BLUSTERY DAY TIMES.
OVERALL SOUTH OF I80...P/C...POSSIBLY A FLURRY OR 2. THE WCI MAY
DROP TO 10 BELOW ZERO IN THE POCONOS THU NIGHT.

FRIDAY...COLD INTERLUDE WITH INCREASING CLOUDS POSSIBLE?

NEXT WEEKEND...POTENTIAL FOR PERIODS OF WINTRY PCPN...ESPECIALLY
SATURDAY...DEPENDING ON SFC LOW EVOLUTION ON A NEW COLD FRONT
CROSSING EASTWARD FROM THE APPALACHIANS. RIGHT NOW OUR FCST IS
HINGED COMPLETELY ON WPC GUIDANCE. ITS CATEGORICAL THAT IT WILL
PRECIPITATE BUT CONFIDENCE ON DETAILS INCLUDING TEMPS AND PTYPE IS
WELL BELOW AVERAGE.THE FCST DRAWN UP FOCUSES PCPN ON SATURDAY ENDING
SATURDAY EVENING.

NEXT MONDAY...BLUSTERY AND COLD...AT LEAST TO START. THE WCI MAY
DROP TO 10 BELOW IN THE POCONOS EARLY MONDAY BUT CONFIDENCE ON
COLD TEMPS MONDAY IS LESS THAN THE HIGH CONFIDENCE FCST FOR
WEDNESDAY-FRIDAY.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

LATE-DAY...IFR CONDITIONS WILL CONTINUE THROUGH THE REMAINDER OF THE
AFTERNOON. WEST/NORTHWEST WINDS WILL BE LESS THAN 10 KT.

TONIGHT...IFR IS FORECAST TO TRANSITION TO MVFR BEFORE THE NEXT
ROUND OF PRECIPITATION SETTLES INTO THE REGION. NORTHWEST WINDS WILL
BE LESS THAN 10 KT.

TUESDAY...MVFR WILL QUICKLY TRANSITION INTO IFR AS SNOW SETTLES IN
ACROSS THE TERMINALS. A PERIOD OF LIFR IS POSSIBLE IN SOME HEAVIER
SNOW. SOME IMPROVEMENT, MVFR, CAN BE EXPECTED LATER IN THE DAY.

OUTLOOK...
TUESDAY NIGHT...VFR NW WIND GUST TO 20 KT. CONFIDENCE ABOVE AVG.

WEDNESDAY - THURSDAY...VFR SCT-BKN AOA 3500 FT. CHANCE OF A FLURRY
EXCEPT A FEW PERIODS OF MVFR OR IFR CONDS IN SNOW SHOWERS AR
POSSIBLE IN THE POCONOS. W-NW WIND G 20-25 KT EACH AFTN.
CONFIDENCE ABOVE AVERAGE. I DID RAISE 12Z/9 NCEP MOS GUIDANCE BY
ABOUT 4 DEGREES PRIMARILY BECAUSE OF STILL RELATIVELY MILD 850
TEMPS AND THE 12Z/9 UK AND EC 2M TEMPS.

FRIDAY...VFR CIGS. WIND TURNING WEST OR SOUTHWEST IN THE AFTN.

SATURDAY...MVFR OR IFR CONDS PROBABLE IN PCPN.

&&

.MARINE...
TONIGHT...NO HEADLINES WITH DIMINISHING WINDS AND SEAS IN THE 2 TO 4
FOOT RANGE.

TUESDAY...BOTH NORTHWEST WINDS AND SEAS WILL BEGIN TO BUILD LATER
TOMORROW. GUIDANCE SUGGESTS THAT SCA CONDITIONS WILL BE BACK IN
PLACE LATE TOMORROW AFTERNOON OR EARLY TOMORROW EVENING.

OUTLOOK...
TUESDAY NIGHT - THURSDAY...A FAIRLY TIGHT GRADIENT WILL PERSIST WITH
PERIODS OF GUSTY WINDS TO 25 KT AND END OF WESTERLY FETCH SEAS ON
THE ATLANTIC NEAR 5 FT.  WE MAY HAVE NEAR GALE FORCE GUSTS TUESDAY
NIGHT AND WEDNESDAY MORNING, ESPECIALLY ACROSS THE NORTHERN OCEAN
WATERS. SCA HAS BEEN STARTED. AN EXTENSION PROBABLE AND IT MAY
NEED AN UPGRADE TO A MARGINAL GALE IN LATER FCST FOR A PTN OF TUE
NIGHT.

FRIDAY...WINDS AND SEAS SHOULD SUBSIDE BELOW SMALL CRAFT ADVISORY
LEVELS AS HIGH PRESSURE BUILDS ACROSS THE REGION AND REMAIN BELOW
AS WE END THE WORK WEEK.

SATURDAY...AN SCA IS POSSIBLE. THERE IS MODEL SPREAD ON THE
SOLUTIONS BUT ITS EVEN POSSIBLE WE`LL NEED A SLY GALE FOR A PTN
OF THE ATLANTIC WATERS. THIS PART OF THE FCST IS VERY LOW
CONFIDENCE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY FROM 6 AM TO 5 PM EST TUESDAY FOR
     PAZ060>062-101-103-105.
     WINTER STORM WARNING FROM 6 AM TO 5 PM EST TUESDAY FOR PAZ070-
     071-102-104-106.
NJ...WINTER WEATHER ADVISORY FROM 6 AM TO 5 PM EST TUESDAY FOR
     NJZ007>010-012>014-020>027.
     WINTER STORM WARNING FROM 6 AM TO 5 PM EST TUESDAY FOR
     NJZ015>019.
DE...WINTER WEATHER ADVISORY FROM 6 AM TO 5 PM EST TUESDAY FOR
     DEZ002>004.
     WINTER STORM WARNING FROM 6 AM TO 5 PM EST TUESDAY FOR DEZ001.
MD...WINTER WEATHER ADVISORY FROM 6 AM TO 5 PM EST TUESDAY FOR
     MDZ012-015-019-020.
     WINTER STORM WARNING FROM 6 AM TO 5 PM EST TUESDAY FOR MDZ008.
MARINE...SMALL CRAFT ADVISORY FROM 5 PM TUESDAY TO 6 AM EST WEDNESDAY
     FOR ANZ430-431-450>455.

&&

$$
SYNOPSIS...DRAG
NEAR TERM...KRUZDLO
SHORT TERM...KRUZDLO
LONG TERM...DRAG
AVIATION...DRAG/KRUZDLO
MARINE...DRAG/KRUZDLO