-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 230924
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
424 AM EST FRI JAN 23 2015

.SYNOPSIS...
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HIGH PRESSURE MOVES OVERHEAD TODAY WHILE A QUICK MOVING LOW PRESSURE
SYSTEM TRACKS ALONG THE EAST COAST LATER TONIGHT. THE LOW WILL MOVE
OFF TOWARDS NEW ENGLAND SATURDAY MORNING WITH A BRIEF SHOT OF HIGH
PRESSURE TO FOLLOW. ANOTHER CLIPPER SYSTEM IS EXPECTED TO MOVE
ACROSS THE REGION EARLY MONDAY MORNING. LARGE ARCTIC HIGH PRESSURE
FILLS IN ON TUESDAY.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
INTERLUDE NICE DAY WITH TEMPERATURES NEAR OR JUST BELOW NORMAL. SUNSHINE
THROUGH VARIABLE HIGH CLOUD THIS MORNING WITH LOW CLOUD IN CENTRAL PA
PROBABLY REDEVELOPING NORTHEASTWARD THIS AFTERNOON AS A LIGHT NORTHWEST
WIND THIS MORNING TURNS SOUTHWEST. MAX SPEEDS UNDER 15 MPH.

TEMPS WERE MAINLY THE WARMER 00Z/23 GFS MAV MOS WITH DEWS/WINDS
BLENDED 00Z/23 GFS/NAM MOS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
WINTER WEATHER ADVISORIES ISSUED FOR MUCH OF THE AREA IN SIX
SEGMENTS TO PERMIT MORE SPECIFIC TIMING AND SNOW/ICE AMOUNTS.

THERE WILL BE ADJUSTMENTS TO THE EXPECTED REALITY OF SNOW AND ICE.

IT WAS A CLOSE CALL ON COMBINED WARNING AMOUNTS FOR THE INTERSTATE
95 CORRIDOR AND 40 MILES TO THE NORTHWEST INCLUDING CHESTER...
MONTGOMERY...BUCKS COUNTIES IN PA ...HUNTERDON AND SOMERSET IN NJ.
WE OPTED FOR THE MORE CONSERVATIVE APPROACH.

NEVERTHELESS...PLEASE MONITOR FUTURE AFTERNOON FORECASTS FOR A
POSSIBLE UPGRADE.

WE THINK 3 TO 6 INCHES OF SNOW JUST NW OF I95 AND UP TO .15 INCH
ICE EXCEPT ALL OR MAINLY SNOW FROM NORTHWEST BERKS COUNTY THROUGH
THE LEHIGH VALLEY INTO WARREN AND SUSSEX COUNTIES NORTHWARD WITH
AMOUNTS OF SNOW THERE 3-6 INCHES. YOU WILL BE SHOVELING THERE
TOMORROW MORNING AND TRAVEL WILL BE SLOW.

ITS POSSIBLE THERE WILL BE ICE ACCUMS APPROACHING 1/4 INCH WITHIN
15 MILES OF I95 SATURDAY MORNING.

ICY SLIPPERY TRAVEL SHOULD OCCUR FOR A FEW HOURS LATE THIS
EVENING INTO PART OF THE NIGHT FOR SNJ MUCH OF DELAWARE AND
MARYLAND`S LOWER EASTERN SHORE.

HOW FAR SOUTH THE ICY AND SNOW...THAT IS LESS CONFIDENTLY EXPRESSED.

WE RAN THIS FORECAST PRIMARILY OFF THE NAM WITH TOP DOWN AND
PARTIAL THICKNESS WEATHER EVALUATION...CHANGING ALL SLEET TO
FREEZING RAIN AS THE BOUNDARY LAYER DOES NOT LOOK COLD ENOUGH TO
CHANGE ANY MELTED SNOW BACK TO ICE PELLETS...SAVE FOR MAYBE AN
HOUR DURING THE TRANSITION.

SNOW COULD BE HEAVY FOR AN HOUR OR SO IN THE WINDOW OF ROUGHLY 4Z
AND 10Z.

A FRONT END SNOW THUMP FOR MUCH OF THE AREA THEN TRANSITIONING TO A
COLD RAIN FROM SSE TO NNW.

RAIN WILL BE HEAVY EARLY SATURDAY OVER THE REGION NEAR AND EAST
OF I95.

SO...THE TEMP FCST TONIGHT WAS MOSTLY THE NAM MOS BLENDED WITH ITS
2M TEMP FCST. THE GFS MOS LOOKED TOO WARM AND THE ECMWF SUPPORT
THE COLDER SCENARIO.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
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MEDIUM RANGE GUIDANCE IS IN DECENT AGREEMENT WITH PACIFIC RIDGING
ALLOWING FOR MEAN EAST COAST TROUGHING THROUGH A MAJORITY OF THE
LONGTERM PERIOD. AT LEAST TWO DISTINCT WAVES MOVE THROUGH THIS MEAN
TROUGH THIS WEEKEND INTO EARLY NEXT WEEK, EACH CARVING INTO THE BASE
OF THE TROUGH. A WEAKENING IN THE PACIFIC RIDGING TOWARDS THE END OF
THE PERIOD SHOULD ALLOW FOR SLIGHTLY MORE ZONAL FLOW TO COMMENCE.

SATURDAY...RAPIDLY DEEPENING SYSTEM ACROSS OUR WATERS WILL BE
QUICKLY MOVING BY TO THE NORTHEAST. 0C 850MB ISOTHERM CONTINUES TO
RUN INLAND THOUGH IT SHOULD STOP SOMEWHERE JUST SOUTH AND EAST OF AN
RDG-UKT-SMQ LINE LATE IN THE MORNING BEFORE SHIFTING BACK TOWARDS
THE EAST BY EARLY AFTERNOON. THERE DOES NOT LOOK TO BE A LOT OF COLD
AIR IN PLACE AND WITH THE LACK OF BLOCKING DOWNSTREAM THIS SYSTEM
MUST CONTINUE TO MAKE ITS OWN COLD AIR. STILL THINK THE BEST CHANCES
FOR AN ALL SNOW EVENT ARE ACROSS THE LEHIGH VALLEY AND POCONOS/NNJ
THOUGH SOME RIMING OF THE SNOW WILL MORE THAN LIKELY TAKE PLACE IN
THE SOUTHERN EXTENT OF THESE AREAS...LOWER SLR EXPECTED. HAVE A
DECENT CHANCE AT SEEING AN ADDITIONAL 1-2" ACROSS NNJ SATURDAY
AFTERNOON. BY LATER IN THE AFTERNOON THE SYSTEM WILL BE TO OUR
NORTHEAST AND WE SHOULD BE DRY EVERYWHERE. IT IS POSSIBLE THAT LATE
IN THE AFTERNOON WE LOSE THE ICE CRYSTALS TO PRODUCE THE SNOW AND
THEREFORE WOULD END UP BEING A FREEZING DRIZZLE...IF THE COLUMN CAN
STAY SATURATED LONG ENOUGH.

SUNDAY - MONDAY...BRIEF SHOT OF HIGH PRESSURE FOR MOST OF SUNDAY,
AHEAD OF ANOTHER WEAK CLIPPER SYSTEM. LIGHT SNOW SHOULD BEGIN TO
OVERSPREAD THE REGION LATE SUNDAY NIGHT/EARLY MONDAY MORNING, FROM
THE WEST. THERE COULD BE SOME MIXING ACROSS OUR EXTREME SOUTHERN
ZONES WITH THE CURRENT TRACK OF THIS SYSTEM, WHICH IS A BIT FARTHER
NORTH THAN PREVIOUS RUNS...USED A PARTIAL THICKNESS OFF THE GFS FOR
PTYPE. TOO SOON TO TALK ABOUT ACCUMULATIONS, LET GET THROUGH
TONIGHT`S EVENT FIRST, BUT MINOR ACCUMULATIONS ARE POSSIBLE.

TUESDAY - THURSDAY...ARCTIC HIGH PRESSURE BUILDS TOWARD THE AREA.
DRY WEATHER WITH BELOW NORMAL TEMPS EXPECTED. HIGHS WED WILL BE
MOSTLY BELOW FREEZING ACROSS THE FORECAST AREA AND A FEW DEGREES
HIGHER THU. LOWS TUE NIGHT AND WED NIGHT WILL BE IN THE SINGLE
DIGITS (AND CLOSER TO ZERO) OVER THE SRN POCONOS AND IN THE TEENS
ELSEWHERE.
-- End Changed Discussion --

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THIS MORNING...VFR CLEAR OR CIRRUS THIS MORNING WITH CIGS 2500-3500
VCNTY KRDG AND KILG REMAINING JUST SOUTH. LIGHT NORTHWEST WIND.

THIS AFTERNOON...WIND TURN LIGHT SOUTHWEST...MAX GUST 15 KT. CIGS
2500-3500 FT SLIDING NEWD AS PER TAFS. CONFIDENCE ON TIMING THE
ARRIVAL IS LESS THAN IDEAL BUT IT APPEARS TO ME THE NAM HAS BEEN
VERY GOOD THE LAST SEVERAL DAYS ON ITS TSECTIONS.

TONIGHT...IFR OR LIFR CONDITIONS IN SNOW SPREADING NORTHWARD PER
THE TAFS. SNOW MAY BRIEFLY CHANGE TO SLEET BEFORE TO FREEZING RAIN
AND THEN RAIN KPHL/KILG/KMIV AND KACY LATER TONIGHT. 1 TO 3 INCHES
OF SNOW AT THESE AIRPORT BEFORE THE CHANGE TO FREEZING RAIN.

VCNTY KPNE AND KTTN...SNOW TO FREEZING RAIN OVERNIGHT 2 TO 4
INCHES BY 12Z.

VCNTY KABE AND KRDG..MOSTLY SNOW WITH 2-4 INCHES AT NEAR 30F BY
12Z SATURDAY.

A 1 TO 2 HOUR PERIOD OF 1/2SM MODERATE SNOW APPEARS PROBABLE AT
MANY AIRPORTS.

PLOWING ANTICIPATED AT MOST AIRPORT FOR A TIME TONIGHT.

DEICING PROBABLY NEEDED FOR THE WETTER SNOW AND OR FREEZING RAIN.

FORTUNATELY MOST OF THE SNOW AND ICE IS AFTER HEAVIER ARRIVAL
DEPARTURES.

WIND LIGHT DURING THE EVENING TURNING NE WITH GUSTS 12-22KT BY 12Z
SATURDAY.

CONFIDENCE: ABOVE AVERAGE ON THE SCENARIO OUTLINED...TIMING COULD BE
IN ERROR BY 2 HOURS. GOES FROM VFR 10 MILES TO IFR VSBY NEAR 1
MILE... PROBABLY WITHIN 30 TO 60 MINUTES OF SNOW ONSET. BASICALLY
A WALL OF SNOW MOVING NORTHWARD.


OUTLOOK...
SATURDAY...WIDESPREAD LIFR/IFR WITH SNOW AND RAIN AFFECTING MUCH OF
THE AREA.

SAT NIGHT/SUN...IMPROVING CONDITIONS SAT NIGHT. VFR SUNDAY.

SUN NIGHT...CONDITIONS DIMINISHING WITH IFR POSSIBLE AND SNOW BY
DAWN MON.

MON...MVFR/IFR WITH LOWER CIGS/VSBYS IN SNOW.

MON NIGHT - TUE...MOSTLY VFR.
-- End Changed Discussion --

&&

.MARINE...
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LIGHT WIND TODAY.

SCA CONDITIONS DEVELOP AFTER 08Z...ESPECIALLY DELAWARE WATERS AS A
NOREASTER RACES NEWD TO PASS EAST OF THE DELMARVA NEAR SUNRISE
SATURDAY.

.OUTLOOK...
SATURDAY - SUNDAY...SCA CONDITIONS EXPECTED AS LOW PRESSURE SYSTEM
PASSING BY. ELEVATED SEAS MAY LINGER A BIT INTO SUNDAY AFTERNOON.

MONDAY - TUESDAY...POSSIBLE SCA/LOW END GALES AS ANOTHER LOW
PRESSURE DEEPENS OFF THE COAST.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST
     SATURDAY FOR PAZ060>062-101-103-105.
     WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 1 PM EST
     SATURDAY FOR PAZ054-055.
     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST
     SATURDAY FOR PAZ070-071-102-104-106.
NJ...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST
     SATURDAY FOR NJZ007>010.
     WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 4 AM EST
     SATURDAY FOR NJZ016-021>023.
     WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 1 PM EST
     SATURDAY FOR NJZ001.
     WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 7 AM EST
     SATURDAY FOR NJZ013-017>020-027.
     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST
     SATURDAY FOR NJZ012-015.
DE...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 4 AM EST
     SATURDAY FOR DEZ001.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 3 AM EST
     SATURDAY FOR DEZ002.
MD...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 4 AM EST
     SATURDAY FOR MDZ012.
     WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 10 AM EST
     SATURDAY FOR MDZ008.
     WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 3 AM EST
     SATURDAY FOR MDZ015-019-020.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM SATURDAY TO 10 AM EST SUNDAY
     FOR ANZ450>455.
     SMALL CRAFT ADVISORY FROM 7 AM TO 6 PM EST SATURDAY FOR ANZ431.
-- End Changed Discussion --

&&

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