Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KPHI 262107
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
407 PM EST MON JAN 26 2015

.SYNOPSIS...
A RAPIDLY INTENSIFYING LOW PRESSURE SYSTEM EAST OF THE VIRGINIA
CAPES WILL MOVE NORTHEAST AND PASS NEAR CAPE COD MASSACHUSETTS
DURING THE MIDDLE OF THE DAY ON TUESDAY BEFORE WEAKENING AS IT MOVES
TOWARD THE CANADIAN MARITIMES ON WEDNESDAY. A HIGH PRESSURE SYSTEM
FROM THE WEST IS EXPECTED TO ARRIVE OVER THE REGION ON WEDNESDAY
NIGHT. A CLIPPER TYPE LOW PRESSURE SYSTEM IS EXPECTED TO FOLLOW WITH
ITS COLD FRONT MOVING THROUGH EARLY FRIDAY. ANOTHER HIGH PRESSURE
SYSTEM IS THEN ANTICIPATED FOR SATURDAY. ANOTHER LOW PRESSURE SYSTEM
SHOULD MOVE THROUGH THE EASTERN UNITED STATES LATE SUNDAY OR EARLY
MONDAY.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
MAJOR WINTER STORM IS STARTING TO WIND UP WITH SFC PRESSURE FALLS
INCREASING OFF THE MID-ATLANTIC COAST AND LOCAL MSAS SHOWS 997 MB
LOW NE OF CAPE HATTERAS. IR STLT SHOWS UPPER TROF SWINGING INTO NEG
TILT AND DOWNSTREAM BAROCLINIC LEAF PATN WITH COOLING CLOUD TOPS.
RADAR SHOWS MOSTLY LIGHT PRECIP/SNOW OVER THE AREA...EXCEPT FOR SOME
LOCALLY STGR ECHOS OVER SRN DEL ASSOCD WITH MDT RAIN AND LOW LEVEL
CONVERGENCE ALONG THE COAST. RAIN OR MIXED PRECIP THIS AFTN OVER DE
AND SRN NJ SHOULD CHANGE OVER TO SNOW THIS EVENING AS COLDER LOW-LVL
AIR IS ADVECTED IN BY WINDS BACKING TO THE NORTH.

WARNINGS AND ADVISORIES FROM EARLIER TODAY HAVE BEEN LEFT IN PLACE
AS THERE DID NOT SEEM TO BE ANY GOOD REASON TO CHANGE THEM. THE
STORM TOTAL SNOW AMOUNT GENERALLY FOLLOWS WWD GUIDANCE...WITH MINOR
ADJUSTMENTS...AND IS NOT A WHOLE LOT DIFFERENT FROM EARLIER AMOUNTS.
THE HIGHEST AMOUNTS...CLOSE TO 2 FEET...ARE STILL IN NERN NJ WITH
AMOUNTS DECREASING S AND W FROM THERE. THE SNOW GRADIENT MAY BE
TIGHTER ON THE WEST SIDE THAN SUGGESTED BY THE STORM TOTAL MAP...BUT
THE MAPS ALSO REFLECTS UNCERTAINTY ABOUT WHERE THE TIGHTEST GRADIENT
MAY BE.

FORECAST FRONTO-GENESIS INDICATES THAT SOME BANDS OF HEAVY SNOW WILL
DEVELOP LATER THIS EVENING AND OVERNIGHT ACROSS SRN NEW ENGLAND AND
WILL EXTEND SWWD INTO PARTS OF NRN NJ. THESE BANDS WOULD BE
RESPONSIBLE FOR THE HIGHEST SNOW AMOUNTS. SNOWFALL RATES OF 2 INCHES
PER HOUR ARE LIKELY AT TIMES IN THE OVERNIGHT HOURS FOR PARTS OF NRN
AND CNTRL NJ.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
IT LOOKS LIKE THE SFC LOW WILL REACH ITS DEEPEST POINT SOMETIME
AROUND 12Z TO 15Z TUESDAY MORNING SOMEWHERE SOUTH OF CAPE COD OR
EASTERN LONG ISLAND. SOME WRAP-AROUND BANDS OF HEAVY SNOW WILL
LIKELY BE CONTINUING OVER NRN NJ FOR A WHILE IN THE MORNING BUT WILL
START TO WEAKEN AND/OR MOVE NEWD BY MID-DAY. A FEW MORE INCHES OF
ACCUMULATION ARE EXPECTED IN THE MORNING BUT NOT MUCH ELSE IN THE
AFTERNOON. POPS ON TUES GO FROM CATEGORICAL IN THE MORNING TO NONE
OR SLGT CHC IN THE LATE AFTN...DECREASING FROM SW TO NE AS THE STORM
PULLS AWAY. GUSTY WINDS MAY CAUSE BLOWING SNOW TO CONTINUE EVEN
THOUGH PRECIP HAS ENDED.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
THE GFS INITIALIZATION LOOKED SLIGHTLY BETTER THAN THE WRF-NMMB. THE
TROF ITSELF LOOKED SLIGHTLY BROADER, NOT AS SHARP, BUT ALREADY WAS
TAKING A SLIGHTLY NEGATIVE TILT. THERMALLY 850MB AND 925MB IT WAS A
MIXTURE OF GFS AND WRF-NMMB.

OVERALL THERE HAS NOT BEEN THAT MUCH OF A CHANGE IN THE LONG TERM
WITH A CLIPPER TYPE SYSTEM FOR THURSDAY NIGHT AND POSSIBLY A
STRONGER SYSTEM LATE SUNDAY INTO MONDAY. IT WILL BE UNSEASONABLY
COLD AND MOST IF NOT ALL OF THE PCPN WILL BE IN THE FORM OF SNOW.

FOR TUESDAY NIGHT EVEN LOOKING AT THE SLOWEST MODELING SOLUTIONS,
THEY BARELY HAVE ANY MEASURABLE IN OUR CWA. THE FASTER CAN
GGEM/UKMET/GFS SNOW IS LONG GONE. WE REMOVED POPS EXCEPT FOR FAR
NERN CWA AND POSSIBLY SOME LAKE EFFECT SNOW SHOWERS MAKING IT INTO
THE POCONOS. WINDS WILL BE DECREASING, BUT WIND CHILL FACTORS WILL
STILL FALL INTO THE SINGLE NUMBERS AND BELOW ZERO NORTHWESTERN
CWA. BECAUSE OF THE FRESH SNOW COVER, WE SIDED WITH THE COLDER
DATASETS, CLOSER TO NAM MOS.

A QUIETER DAY ON WEDNESDAY WITH HIGH PRESSURE NOSING CLOSER TO OUR
AREA. THE PREDICTED LOW LEVEL MOISTURE DOES NOT LOOK THAT IMPRESSIVE
AND SKIES SHOULD BE MOSTLY SUNNY. EVEN SO, WE LIKELY WILL NOT REACH
THE FREEZING MARK IN THE BULK OF OUR CWA.

WEDNESDAY NIGHT WILL BE A VERY COLD NIGHT. HOW COLD WILL DEPEND UPON
HOW QUICKLY CLOUDINESS STARTS MOVING ACROSS FROM THE NEXT CLIPPER
LIKE SYSTEM. WINDS WILL BE LIGHT REGARDLESS. WE ARE COLDER THAN
ALL OF THE GUIDANCE DATASETS WITH MIN TEMPS AND IN REALITY MAY
NOT BE COLD ENOUGH.

DECREASING SUNSHINE AS THURSDAY PROGRESSES. THERE IS GOOD MODELING
CONSENSUS OF MID LEVEL OMEGA AND QVEC CONVERGENCE WITH THIS SYSTEM
ARRIVING BY 00Z. GIVEN THAT THE WAA PHASE LIKES TO SNEAK IN EARLY,
WE KEPT PCPN CHANCES IN FOR LATE IN THE DAY. PTYPE SHOULD BE
PRIMARILY SNOW. SOME MIXING BASED ON FCST 925MB TEMPS ABOVE ZERO
MIGHT OCCUR FAR SE.

THE BULK OF THE CLIPPER PCPN IS EXPECTED TO OCCUR AT NIGHT. ASSUMING
IT DOES NOT ARRIVE IN TIME FOR THE EVENING COMMUTE, ITS APPEARING TO
BE A BORDERLINE ADVISORY CRITERIA TYPE EVENT SNOW. PCPN SHOULD
END BY FRIDAY MORNING WITH A WINDIER DAY IN WAKE OF THE SYSTEM`S
COLD FRONT.

COLDER WEATHER FOR FRIDAY NIGHT AND SATURDAY AS THE NEXT
ARCTIC/CANADIAN AIR MASS MOVES EASTWARD. WE THEN REPEAT THE PROCESS
LATER IN THE WEEKEND AS THE HIGH PRESSURE SYSTEM MOVES OFFSHORE AND
ANOTHER FRONT APPROACHES THE REGION. ANOTHER LOW PRESSURE SYSTEM IS
FORECAST TO FORM ON THE FRONT. THIS ONE COULD TAP GULFMEX MOISTURE
AND THUS BE A SNOWIER SYSTEM.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

**HIGH IMPACT EVENT, ESPECIALLY TONIGHT AND TUESDAY MORNING**

THROUGH LATE-DAY...LIGHT SNOW IS EXPECTED TO CONTINUE ACROSS THE
AREA THROUGH THIS AFTERNOON, WITH MOSTLY MVFR TO POSSIBLE IFR
CONDITIONS. GUSTY NORTHEAST WINDS WILL PERSIST, WITH GUSTS MAINLY
BETWEEN 25 TO 30 KNOTS, ESPECIALLY FROM THE DELAWARE VALLEY EASTWARD
TO THE COAST.

EVENING/OVERNIGHT/EARLY TUESDAY...STEADILY DETERIORATING CONDITIONS
ARE EXPECTED THROUGH THIS PERIOD, WITH MODERATE TO AT TIMES HEAVY
SNOW DEVELOPING. SNOWFALL RATES OF ONE TO TWO INCHES PER HOUR ARE
POSSIBLE AT TIMES, ESPECIALLY THROUGH NJ AND THE DELAWARE VALLEY.
IFR TO LIFR CIGS AND VSBYS ARE EXPECTED. GUSTY NORTH-NORTHEAST WINDS
WILL CONTINUE, WITH GUSTS TO AROUND 30 KNOTS AT TIMES. AREAS OF
BLOWING SNOW ARE EXPECTED.

REST OF TUESDAY...AROUND MIDDAY AND INTO THE AFTERNOON, IMPROVEMENT
TO MVFR CONDITIONS ARE EXPECTED WITH SOME CONTINUED LIGHTER SNOW
ACROSS THE REGION. BLOWING AND DRIFTING SNOW WILL BE AN ISSUE,
THOUGH, AS WINDS BACK MORE TOWARD THE NORTHWEST WITH CONTINUED GUSTS
INTO THE 25 TO 30 KNOT RANGE. SOME LATE-DAY IMPROVEMENT TO VFR IS
EXPECTED, BUT TIMING IS A LITTLE UNCERTAIN.

OUTLOOK...
TUESDAY NIGHT...VFR. GUSTY NORTHWEST WINDS.

WEDNESDAY AND WEDNESDAY NIGHT...PRIMARILY VFR.

THURSDAY INTO FRIDAY MORNING...VFR TO START THURSDAY THEN LIKELY
BECOMING MVFR OR IFR IN SNOW WITH HIGHEST CONFIDENCE NORTHERN
AIRPORTS AND TERMINALS.

FRIDAY AFTERNOON AND EVENING...VFR WITH GUSTY NORTHWEST WINDS.

FRIDAY OVERNIGHT INTO SATURDAY...PRIMARILY VFR.

&&

.MARINE...
STORM AND GALE WARNINGS HAVE BEEN LEFT AS IS. WINDS ARE FCST TO
INCREASE TONIGHT INTO TUESDAY AS LOW PRESSURE OFF THE MID-ATLANTIC
COAST DEEPENS TO AROUND 975 MB BY 1200Z TOMORROW MORNING. WINDS ARE
EXPECTED TO GUST TO NEAR 50 KT NORTH OF CAPE MAY AND 40 TO 45 KT
SOUTH. SEAS WILL BUILD TO 10 TO 12 FT OR HIGHER TONIGHT  WITH THE NE
FETCH. WINDS AND SEAS WILL GRADUALLY SUBSIDE ON TUESDAY BUT CONDS
WILL REMAIN QUITE ROUGH. ALSO...VSBY WILL BE VERY POOR AT TIME
TONIGHT AND TUESDAY MORNING IN BANDS OF HEAVY SNOW.

OUTLOOK...
TUESDAY NIGHT...WE WILL BE TRANSCENDING FROM GALES INTO SMALL CRAFT
ADVISORY CONDITIONS. FREEZING SPRAY.

WEDNESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED WITH
FREEZING SPRAY.

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...NO MARINE HEADLINES ARE
ANTICIPATED. SOME FREEZING SPRAY POSSIBLE WEDNESDAY NIGHT.

FRIDAY AND SATURDAY...A SCA SHOULD EVENTUALLY BE NEEDED FRIDAY AS A
NORTHWEST FLOW OF COLD AIR ADVECTION DEVELOPS BEHIND THE DEPARTING
CLIPPER LOW. WE MIGHT COME CLOSE TO GALE FORCE GUSTS FRIDAY NIGHT.
WINDS SHOULD START DECREASING BELOW SMALL CRAFT ADVISORY LEVELS ON
SATURDAY.

&&

.TIDES/COASTAL FLOODING...
NO CHANGE FOR THE COASTAL FLOODING HIGHLIGHTS WITH THIS FORECAST.
STILL RELATIVELY HIGH CONFIDENCE OF THE UPPER END OF MINOR TO THE
LOWER END OF MODERATE TIDAL FLOODING ALONG THE ATLANTIC COAST WITH
TONIGHT/S HIGH TIDE CYCLE, SO KEPT THE COASTAL FLOOD WARNING AS IS.
THERE IS LESS CONFIDENCE ON THE UPPER DELAWARE BAY AND THE TIDAL
DELAWARE. BY THE TIME OF THE HIGH TIDE ON THE UPPER BAY, WINDS
SHOULD HAVE SHIFTED TO NORTHWESTERLY, LIMITING TIDAL DEPARTURES.
MINOR FLOODING IS POSSIBLE, BUT AT THIS TIME CONFIDENCE IS TOO LOW
TO ISSUE ANY COASTAL FLOOD ADVISORIES FOR THESE LOCATIONS.

&&

.CLIMATE...
RECORD (VULNERABLE) DAILY SNOW FALL FOR OUR LONG TERM CLIMATE
SITES. TUESDAY 1/27.

ACY 4.0 1946
PHL 4.1 1941
ILG 2.9 2004
ABE 8.0 1897

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER STORM WARNING UNTIL 6 PM EST TUESDAY FOR PAZ070-071-
     103>106.
     WINTER WEATHER ADVISORY UNTIL 3 PM EST TUESDAY FOR PAZ060-101-
     102.
     WINTER STORM WARNING UNTIL 3 PM EST TUESDAY FOR PAZ054-055-061-
     062.
NJ...WINTER STORM WARNING UNTIL 6 PM EST TUESDAY FOR NJZ001-007>010-
     015>019-021>025-027.
     COASTAL FLOOD WARNING FROM 11 PM THIS EVENING TO 7 AM EST
     TUESDAY FOR NJZ012>014-020>027.
     BLIZZARD WARNING UNTIL 6 PM EST TUESDAY FOR NJZ012>014-020-026.
DE...COASTAL FLOOD WARNING FROM 11 PM THIS EVENING TO 7 AM EST
     TUESDAY FOR DEZ002>004.
     WINTER WEATHER ADVISORY UNTIL 3 PM EST TUESDAY FOR DEZ001>004.
MD...WINTER WEATHER ADVISORY UNTIL 3 PM EST TUESDAY FOR MDZ008-012-
     015-019-020.
MARINE...STORM WARNING UNTIL 6 PM EST TUESDAY FOR ANZ450>453.
     GALE WARNING UNTIL 6 PM EST TUESDAY FOR ANZ430-431-454-455.

&&

$$
SYNOPSIS...DRAG/GIGI
NEAR TERM...AMC
SHORT TERM...AMC
LONG TERM...GIGI
AVIATION...DRAG/GIGI/KLINE
MARINE...AMC/DRAG/GIGI
TIDES/COASTAL FLOODING...JOHNSON
CLIMATE...DRAG





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.