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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 012028
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
328 PM EST SUN FEB 1 2015

.SYNOPSIS...
LOW PRESSURE WILL MOVE THROUGH THE OHIO VALLEY TONIGHT AND CROSS OUR
AREA ON MONDAY BEFORE RACING OFF TO THE NORTHEAST MONDAY NIGHT. HIGH
PRESSURE WILL BUILD ACROSS TO THE SOUTH OF OUR AREA TUESDAY THROUGH
WEDNESDAY. A CLIPPER SYSTEM WILL MOVE ACROSS THE GREAT LAKES REGION
ON WEDNESDAY, DRAGGING A COLD FRONT ACROSS OUR AREA ON THURSDAY.
HIGH PRESSURE WILL THEN RETURN FOR FRIDAY. ANOTHER FRONTAL SYSTEM
WILL CROSS THE REGION OVER THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
A RATHER COMPLEX FORECAST AS SUBTLE CHANGES IN THE THERMAL
PROFILES/MICROPHYSICS WILL AFFECT THE PRECIPITATION TYPES. THIS
FORECAST CARRIES LOWER CONFIDENCE REGARDING THE TIMING OF THE MIXING
OR CHANGEOVER AND THE SOUTHERN EXTENT OF ANY LIGHT ICING.

THE WATER VAPOR IMAGERY THIS AFTERNOON SHOWS A WELL DEFINED
UPPER-LEVEL LOW NEAR THE MID-MISSISSIPPI VALLEY. THIS FEATURE LOOKS
RATHER SHARP AS A STRONGER UPPER-LEVEL JET ROTATES INTO THE BASE OF
THE TROUGH. THIS RESULTS IN A BIT MORE RIDGING IN FRONT OF THE
STORM, THEREFORE A NORTHWARD TRACK OF THE SURFACE LOW. HOWEVER, A
PRONOUNCED AND TIGHTENING BAROCLINIC ZONE IS PRESENT EASTWARD WITH
ARCTIC AIR TO THE NORTH. THIS AT TIMES DOES FORCE THE SURFACE LOW
TRACK A LITTLE FARTHER TO THE SOUTH, HOWEVER GIVEN THE AMPLITUDE OF
THE TROUGH THE WARMING ALOFT LOOKS TO OVERSPREAD THE ENTIRE AREA. AS
A RESULT, THE SNOW THAT DEVELOPS WILL MIX WITH AND CHANGE TO SLEET
AND FREEZING RAIN NORTHWARD WITH EVEN THE PLAIN RAIN PHASE GETTING
RATHER FAR NORTH TOWARD DAYBREAK.

BACKING UP A BIT, THE INCREASING WAA AND ISENTROPIC UPGLIDE WILL
RESULT IN A SWATH OF OVERRUNNING SNOW AS THE LIFT BECOMES FOCUSED
ALONG THE THERMAL GRADIENT. SO FAR THIS IS WEAK WITH ENOUGH DRYING
TO ERODE MUCH OF THE INCOMING PRECIPITATION. THE LOWER LEVELS THOUGH
ARE MOISTENING SOME, WITH SOME FLURRIES OR LIGHT SNOW AT TIMES INTO
PARTS OF OUR WESTERN ZONES THIS AFTERNOON. THIS SNOW COULD THEN COME
IN FAIRLY FAST LATER THIS EVENING WITH PERHAPS A THUMP OF SNOW
/SNOWFALL RATES AROUND AN INCH PER HOUR/ FARTHER NORTH TAILING OFF
TO A PERIOD OF LIGHTER SNOW TO RAIN SOUTHWARD. THERE MAY BE SOME
HEAVIER BANDING ACROSS THE NORTH FOR A TIME OVERNIGHT BEFORE WARMING
ALOFT GETS MORE INVOLVED. THE WARMING LOOKS PRONOUNCED ALOFT TO
ALLOW A QUICKER CHANGEOVER FROM SOUTH TO NORTH OVERNIGHT. THEREFORE,
PORTIONS OF SOUTHEASTERN PENNSYLVANIA ON SOUTH AND EAST SHOULD BE
EITHER MIXING OR CHANGING TO RAIN WELL BEFORE DAYBREAK AS
TEMPERATURES CLIMB TO OR ABOVE FREEZING. SOME PAUSE IS NEEDED THOUGH
AS EVEN THE FARTHER NORTH GUIDANCE SHOWS SOME COLD AIR DAMMING
HOLDING ON JUST ENOUGH FROM THE LEHIGH VALLEY AREA NORTHWARD WHICH
WOULD SLOW THE SURFACE TEMPERATURE RISE. THIS COULD BE ENHANCED BY
THE SNOW COVER THAT EXISTS AND THE GROUND BEING COLD. THIS WILL HAVE
TO BE WATCHED BECAUSE IF THE WARMER AIR FLOODS NORTHWARD FASTER,
THAN MORE OF AN ICING THREAT INCREASES WHILE ACCUMULATING SNOW/SLEET
DECREASES.

WE LEANED MORE TOWARD A GFS/ECMWF BLEND. THIS TENDS TO FAVOR A
QUICKER CHANGEOVER INTO THE PHILADELPHIA METRO, WITH EVEN THE SLEET
TO FREEZING RAIN DRIVING FARTHER NORTH FASTER. AS A RESULT OF A
MODEL CONSENSUS AND COLLABORATION WITH OUR NEIGHBORING OFFICES, WE
CUT BACK ON THE SNOW AMOUNTS AND ADDED MORE ICING. REGARDING THE
WINTER WEATHER ADVISORIES AND WINTER STORM WARNINGS, WE WILL
MAINTAIN THEM WHERE THEY ARE FOR NOW BUT DID DO SOME REGROUPING
ALONG WITH SOME ADJUSTMENTS TO THE END TIMES. WE ARE CONCERNED THAT
THE SOUTHERN TIER OF ADVISORIES MAY NOT BE NEEDED BUT WILL HOLD FOR
NOW SINCE THERE IS A CHC OF A BRIEF MIX/ICING BEFORE JUST RAIN
OCCURS. IF THE GROUND IS COLD ENOUGH, IT DOES NOT TAKE MUCH ICING TO
CAUSE ISSUES. THE SOUTHERN TIER OF THE WARNINGS MAY END UP FALLING
SHORT OF CRITERIA HOWEVER BASED ON COMBINED IMPACTS OF SNOW AND ICE
WE STAYED THE COURSE ATTM.

AS FOR THE LOW TEMPERATURES, WE USED A NAM/GFS MOS AND ECMWF BLEND.
THE HOURLY GRIDS WERE SET TO SHOW TEMPERATURES RISING OVERNIGHT,
WITH THIS TREND MORE PRONOUNCED FROM THE PHILADELPHIA METRO ON SOUTH
AND EAST. THIS TREND WILL HAVE TO BE MONITORED AS IT WILL HAVE AN
IMPACT ON THE PROJECTED ICING.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
THE AFOREMENTIONED SHORT WAVE TROUGH WILL MOVE ACROSS THE AREA
DURING THE DAY MONDAY. THIS WILL TAKE SURFACE LOW PRESSURE RIGHT
OVER OUR AREA, AND WITH WARMING OCCURRING MUCH OF THE CWA MAY GO
OVER TO PLAIN RAIN FOR AWHILE. HOWEVER, FROM ABOUT THE LEHIGH VALLEY
REGION NORTHWARD JUST ENOUGH COLD AIR DAMMING MAY GET TRAPPED DUE TO
SNOW COVER AND ICE TO NOT ALLOW THE WARMER AIR ALOFT TO PENETRATE
DOWN TO THE SURFACE. THIS COULD RESULT IN MORE ICING ACROSS THESE
AREAS. IT APPEARS THAT FARTHER SOUTH, ANY MIXING EARLY SHOULD BE
MAINLY RAIN BUT EVEN INTO THE I-95 AREA SOME CAUTION IS ADVISED
EARLY AS A COLD GROUND MAY RESULT IN SOME ICY SPOTS DESPITE THE AIR
TEMPERATURE RISING.

WE THEN TURN OUR ATTENTION TO THE RAPID INCREASE IN CAA AS THE STORM
DEPARTS. THE GUIDANCE IS IN GOOD AGREEMENT IN RAPIDLY INCREASING
THE CAA, WHICH WOULD RESULT IN THE TEMPERATURES TUMBLING DURING THE
AFTERNOON FROM WEST TO EAST. IF THIS OCCURS FAST ENOUGH, ANY RAIN OR
MIXED PRECIPITATION WOULD CHANGE TO SNOW BEFORE ENDING. IN ADDITION,
THE WET /SLUSHY/ SURFACES MAY UNDERGO A FLASH FREEZE AS TEMPERATURES
RAPIDLY DROP BELOW FREEZING BY EVENING.

THE EXTENT OF THE CAA SURGE COMBINED WITH PRESSURE RISES AND A TIGHT
PRESSURE GRADIENT WILL RESULT IN A SHARP INCREASE IN THE WINDS
MONDAY AFTERNOON AS THE LOW-LEVEL INVERSION BREAKS. THIS INCREASED
MIXING SHOULD RESULT IN WIND GUSTS ON THE ORDER OF 30-40 MPH. WHILE
THIS WILL HELP DRY SOME OF THE SURFACES OUT WITH TIME, A SUDDEN DROP
IN TEMPERATURES TO BELOW FREEZING CAN STILL RESULT IN A FREEZE UP OF
UNTREATED SURFACES.

AS FOR THE HIGH TEMPERATURES, WE USED A NAM/GFS MOS AND ECMWF BLEND
WITH SOME TWEAKS. THE TEMPERATURES WERE THEN SHOWN TO FALL IN THE
AFTERNOON FROM WEST TO EAST, HOWEVER WE MAY NOT NECESSARILY BE
CATCHING THE MAGNITUDE OF THIS DROP IN THE HOURLY GRIDS.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
MONDAY NIGHT...THE SURFACE LOW RACES OFF TO THE NORTHEAST AND WITH
HIGH PRESSURE BUILDING IN FROM THE WEST. THE ATMOSPHERE DRIES OUT
PRETTY QUICKLY AND THE PRECIPITATION WILL CUT OFF JUST AS FAST AS A
RESULT. A FEW FLURRIES MAY CONTINUE INTO THE EVENING BUT EXPECT THEM
TO PETER OUT BEFORE MIDNIGHT.

SKIES WILL CLEAR AND TEMPERATURES WILL CONTINUE TO FALL OVERNIGHT. A
FRESH SNOWPACK IN MANY AREAS WILL CONTRIBUTE TO VERY COLD OVERNIGHT
TEMPERATURES AND WE WILL SEE TEMPERATURES PLUMMET INTO THE SINGLE
DIGITS ACROSS OUR NORTHERN AREAS AND INTO THE LOWER TO MID TEENS
ACROSS THE SOUTHERN AND COASTAL AREAS. IN ADDITION TO THE COLD
TEMPERATURES, WE WILL LIKELY SEE FREEZING OF WET SURFACES AS THE
TEMPERATURES FALL THROUGH THE NIGHT, MAKING EXPOSED AND UNTREATED
SURFACES SLIPPERY.

WINDS WILL REMAIN UP THROUGH THE OVERNIGHT PERIOD AND WE WILL LIKELY
SEE WIND CHILLS INTO THE NEGATIVE TEENS ACROSS THE SOUTHERN POCONOS
AND NORTHWEST NEW JERSEY. WIND CHILL ADVISORIES MAY BE NEEDED FOR
MONDAY NIGHT INTO TUESDAY MORNING ACROSS THESE AREAS.

TUESDAY...HIGH PRESSURE WILL BUILD ACROSS THE REGION TUESDAY,
REMAINING CENTERED TO OUR SOUTH, WITH A SHIFT FURTHER SOUTH AND EAST
TUESDAY NIGHT. PLENTY OF COLD AIR WILL ACCOMPANY THIS HIGH PRESSURE
SYSTEM WITH 850MB TEMPERATURES IN THE -10C TO -15C RANGE. MAXIMUM
TEMPERATURES WILL STRUGGLE TO RISE AND GENERALLY REMAIN IN THE 20S,
WITH TEENS ACROSS THE LEHIGH VALLEY, SOUTHERN POCONOS AND
NORTHWESTERN NEW JERSEY AND SOME LOWER 30S ACROSS OUR SOUTHERNMOST
ZONES.

THE AIR MASS WILL MODIFY A BIT AS IT SLIDES EASTWARD AND MINIMUM
TEMPERATURES WILL NOT BE AS COLD TUESDAY NIGHT AS THEY ARE ON MONDAY
NIGHT. IT WILL STILL BE COLD WITH LOWS RANGING FROM THE SINGLE
DIGITS ACROSS THE HIGHER ELEVATIONS ACROSS THE NORTH TO THE LOWER
20S ACROSS THE SOUTHERN PART OF THE FORECAST AREA.

WEDNESDAY AND THURSDAY...A SURFACE LOW PRESSURE SYSTEM WILL TRACK TO
THE THE NORTH OF THE AREA ON WEDNESDAY WITH ITS ATTACHED COLD FRONT
MOVING THROUGH OUR REGION ON THURSDAY. ANOTHER SYSTEM WILL DEVELOP
IN THE GULF OF MEXICO AND THEN TRACK TOWARD THE CAROLINA COAST ON
THURSDAY. THIS SECOND SYSTEM LOOKS TO REMAIN OFFSHORE AT THIS TIME.
THE COLD FRONT WILL GET PULLED INTO THE COASTAL SYSTEM AND THEN EXIT
QUICKLY TO THE NORTHEAST, REACHING THE CANADIAN MARITIMES BY
THURSDAY NIGHT.

SOME LIGHT SNOW WILL START TO PUSH INTO THE REGION AHEAD OF THE COLD
FRONT ON WEDNESDAY BEFORE STARTING TO OVERSPREAD THE AREA ON
THURSDAY. PRECIPITATION TYPE LOOKS TO BE MAINLY SNOW WITH MAYBE SOME
RAIN MIXING IN ACROSS OUR FAR SOUTHERN AREAS. THE SNOW WILL END
QUICKLY THURSDAY EVENING. TEMPERATURES

MAXIMUM TEMPERATURES ON WEDNESDAY WILL BE QUITE WARM, OR AT LEAST
FEEL THAT WAY. EXPECT HIGHS TO RISE ONTO THE MID 30S TO MID 40S
ACROSS MUCH OF THE AREA. OVERNIGHT LIGHTS INTO THURSDAY MORNING WILL
ONLY FALL INTO THE UPPER TEENS 20S ACROSS MOST OF THE REGION. FOR
THURSDAY, WE WILL SEE A DEFINITELY DECLINE IN TEMPERATURES AS THE
PRECIPITATION IMPACTS OUR AREAS. HIGHS WILL NOT RISE ALL THAT MICH
AND WILL STRUGGLE TO REACH 30, ESPECIALLY AREAS ALONG AND TO THE
NORTH AND WEST OF THE I-95 CORRIDOR. THURSDAY NIGHT WILL BE ANOTHER
COLD ONE AND BUNDLING UP WILL DEFINITELY BE NEEDED. LOWS WILL BE IN
THE 10S TO MID TEENS ACROSS OUR SOUTHERN AND COASTAL AREAS AND ONLY
INTO THE SINGLE DIGITS AS YOU HEAD TO THE NORTH AND WEST. SOUTHERN
POCONOS AND NORTHWEST NEW JERSEY MAY SEE TEMPERATURES FALL INTO THE
MINUS SINGLE DIGITS OVERNIGHT. WIND CHILLS OVERNIGHT WILL MAKE IT
FEEL EVEN COLDER AND AN ADVISORY MAY BE NEEDED ACROSS THE FAR NORTH.

FRIDAY...HIGH PRESSURE WILL SLIDE ACROSS THE OHIO VALLEY AND THEN
SHIFT TO OUR SOUTH FRIDAY NIGHT. HIGHS ON FRIDAY LOOK TO BE COLD
ONCE AGAIN AS THE HIGH PUSHES TO THE EAST. TEMPERATURES INTO THE 20S
CAN BE EXPECTED ACROSS THE FORECAST AREA.

AS THE HIGH SLIDES TO THE SOUTH, A SOUTHWESTERLY FLOW WILL DEVELOP
AND WE SHOULD SEE A BIT OF WARMER AIR REACH OUR AREA. WITH THIS
SOUTHWEST FLOW, OVERNIGHT TEMPERATURES WON`T BE AS COLD AS THURSDAY
NIGHT AND SHOULD RANGE FROM THE SINGLE DIGITS ACROSS THE NORTH TO
AROUND 20 ACROSS THE SOUTH.

SATURDAY AND SUNDAY...A LOW PRESSURE SYSTEM DROPS DOWN FROM CANADA
AND TRACKS INTO NEW ENGLAND. ITS ATTACHED COLD FRONT LOOKS TO DROP
DOWN INTO OUR AREA FROM THE NORTH SATURDAY INTO SUNDAY.
PRECIPITATION THIS FAR OUT LOOKS TO BE SNOW AT THIS TIME.

&&

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

THIS AFTERNOON - TONIGHT...VFR TO START BEFORE DROPPING TO MVFR/IFR
AS LIGHT SNOW MOVES IN FROM THE WEST-SOUTHWEST LATER THIS EVENING.
THE SNOWIEST TERMINALS WILL BE RDG/ABE WHILE THE I-95 TERMINALS SEE
SOME SNOW, WITH A QUICK TRANSITION TO FREEZING RAIN TO
RAIN...MIV/ACY SHOULD BE QUICK SNOW TO RAIN...MINIMAL MIXING
EXPECTED. WINDS WILL OUT OF THE WEST EARLY AND BACKING TOWARDS THE
SOUTH-SOUTHEAST LATE TONIGHT.

MONDAY...IFR TRENDING TO MVFR LATE IN THE CYCLE. RDG/ABE WILL BE THE
LAST TERMINALS TO CHANGE OVER TO ALL RAIN BY LATER MONDAY MORNING.
WINDS BECOME LIGHTER AS THE CENTER OF THE LOW PRESSURE PASSING BY.
MODERATE TO HEAVY RAIN MAY OCCUR LATE MORNING INTO THE EARLY
AFTERNOON. STRONGER WEST-NORTHWEST WINDS KICK IN BEHIND THE SYSTEM
WITH STRONG GUSTS EXPECTED LATE IN THE CYCLE. A CHANGEOVER BACK TO
SOME SNOW SHOWERS IS POSSIBLE LATE AFTERNOON, IF ANY MOISTURE REMAINS.

OUTLOOK...
MONDAY NIGHT...MVFR TO VFR. LINGERING SNOW SHOWERS COME TO AN END
WEST TO EAST. GUSTY NORTHWEST WINDS, UPWARDS OF 25 TO 30 KNOTS
THROUGH EARLY TUESDAY MORNING BEFORE SUBSIDING.

TUESDAY...VFR.

WEDNESDAY - CHANCE OF SNOW SHOWERS WITH LOCAL MVFR/IFR RESTRICTIONS.

THURSDAY - FRIDAY...VFR

&&

.MARINE...
TONIGHT - TUESDAY MORNING...CONVERTED THE GALE WATCH TO A WARNING
ACROSS ALL OUR WATERS STARTING MONDAY EVENING. AHEAD OF THE
NORTHWEST GALES A PERIOD OF SOUTH-SOUTHWESTERLY SCA GUSTS IS
POSSIBLE. A DRAMATIC SHIFT IN THE WINDS IS EXPECTED BY LATE MONDAY
AFTERNOON/EARLY EVENING AS A QUICK MOVING COLD FRONT PUSHES
THROUGH. BEHIND THIS FRONT IS WHEN THE GALES KICK IN. THE STRONG
GUSTS SHOULD BEGIN TO SUBSIDE BY MID-TUESDAY MORNING. LIGHT TO
MODERATE FREEZING SPRAY IS LIKELY ON TUESDAY


OUTLOOK...
TUESDAY - WEDNESDAY...SUB SCA SEAS AND WINDS EXPECTED.

THURSDAY - FRIDAY...POSSIBLE SCA CONDITIONS AS ANOTHER COLD FRONT IS
EXPECTED TO MOVE THROUGH ON THURSDAY. FREEZING SPRAY IS POSSIBLE ON
FRIDAY.


&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 1 PM EST MONDAY
     FOR PAZ060>062-103-105.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST
     MONDAY FOR PAZ070-071.
     WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 PM EST MONDAY
     FOR PAZ054-055.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST
     MONDAY FOR PAZ101-102-104-106.
NJ...WINTER STORM WARNING FROM 7 PM THIS EVENING TO 1 PM EST MONDAY
     FOR NJZ007>010-012.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST
     MONDAY FOR NJZ013-014-016>020-026-027.
     WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 PM EST MONDAY
     FOR NJZ001.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 1 AM EST
     MONDAY FOR NJZ021-022-025.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 10 AM EST
     MONDAY FOR NJZ015.
DE...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST
     MONDAY FOR DEZ001.
MD...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 7 AM EST
     MONDAY FOR MDZ008.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 1 AM EST
     MONDAY FOR MDZ012.
MARINE...GALE WARNING FROM 4 PM MONDAY TO 6 AM EST TUESDAY FOR ANZ430-
     431-450>455.

&&

$$
SYNOPSIS...MEOLA
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...MEOLA
AVIATION...GORSE/HEAVENER
MARINE...GORSE/HEAVENER