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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 080030
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
710 PM EST SAT DEC 7 2013

.SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE OVER THE MID MISSISSIPPI VALLEY WILL BUILD EAST INTO
THE COMMONWEALTH OVERNIGHT...BEFORE BECOMING CENTERED OVER THE NEW
ENGLAND STATES BY SUNDAY NIGHT. ANOTHER ROUND OF SNOW AND SLEET
FOLLOWED BY FREEZING RAIN WILL BECOME FOCUSED ACROSS CENTRAL
PENNSYLVANIA SUNDAY AFTERNOON INTO MONDAY. AN ARCTIC FRONTAL PASSAGE
EARLY NEXT WEEK WILL DROP TEMPERATURES WELL BELOW NORMAL THROUGH THE
MIDDLE AND LATTER PART OF NEXT WEEK.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...

-- Changed Discussion --
THE PRIMARY CHANGE IN WEATHER AND WINTER WEATHER PRODUCTS RESIDES IN
THE SHORT TERM PERIOD WHERE MODIFICATIONS WERE MADE TO THE CURRENT
WINTER STORM WATCH...WITH A WINTER WEATHER ADVISORY ISSUED FOR
PORTIONS OF THE LOWER SUSQ AND EAST CENTRAL MTNS SUNDAY AFTERNOON
INTO MONDAY. MORE ON THAT BELOW...

SFC HIGH CENTERED ACROSS NRN ILLINOIS THIS EVENING WILL BUILD EAST
INTO CENTRAL PENN EARLY SUNDAY. LIGHT NORTHWEST TO NORTH WINDS EARLY
TONIGHT WILL VEER AROUND TO THE EAST EARLY SUNDAY.

AREAS OF BKN-OVC STRATO CU WILL PREVAIL ACROSS THE WRN MTNS OF PA
OVERNIGHT AS THE FAVORABLE OROGRAPHIC...LIGHT NW FLOW SQUEEZES OUT
THE LIMITED LLVL MOISTURE FROM THE UPSTREAM GLAKES. A FEW LIGHT
FLURRIES ARE POSSIBLE ON THE RIDGES TOP TO THE WEST OF ROUTE 219.

ELSEWHERE...A THICKENING SHIELD OF CIRRUS WILL ADVANCE NE ACROSS THE
STATE OVERNIGHT.

LOW TEMPS WILL RANGE FROM THE LOWER TEENS ACROSS THE NORTHERN TIER
COUNTIES....TO THE LOWER 20S ACROSS THE LOWE SUSQ VALLEY/HARRISBURG
METRO AREA.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
-- Changed Discussion --
COLD AIR DAMMING ASSOCIATED WITH DEPARTING/SPRAWLING EAST COAST SFC
RIDGE AXIS WILL BE OVERRUN BY A PERSISTENT SOUTHWEST UPPER FLOW WITH
INCREASING MOISTURE AND PULSES OF ENHANCED ISENT LIFT FROM A FEW
WSWRLY LLJ MAXES.

THESE SUBTLE FORCING FEATURES AND VARYING DEPTH OF THE LLVL COLD
POOL OF AIR WILL CREATE ANOTHER CHALLENGING FORECAST OF A WINTER
WEATHER EVENT HERE IN CENTRAL PENN.

THE LACK OF DEEP/STRONG WAA ALOFT WILL MINIMIZE THE CHANCE FOR HEAVY
QPF AND RAPID CHANGEOVER TO RAIN OR FREEZING RAIN...BUT MORE
IMPORTANTLY LEAD TO THE POTENTIAL FOR A PROLONGED SLEET AND FREEZING
RAIN EVENT SUNDAY NIGHT INTO MONDAY MORNING /AFTER SEVERAL...TO 8
HOUR PERIOD OF LIGHT SNOW.

MODELS BASICALLY AGREE THAT LIGHT PRECIPITATION WILL BREAK OUT BY
LATE MORNING ACROSS THE SOUTH IN THE FORM OF SNOW AND OVERSPREAD
MOST AREAS NORTH OF I-80 BY EVENING. PRECIPITATION IS EXPECTED TO
REMAIN ON THE LIGHT SIDE FOR THE DAYTIME HOURS...WITH ONLY LIGHT
ACCUMS OF SNOW EXPECTED FOR MOST...THOUGH A FEW INCHES OF SNOW ACCUM
ARE POSS ALONG THE MASON/DIXON LINE. HIGHS WILL BE IN THE UPPER 20S
TO LOWER 30S.

AS HIGH RETREATS INTO NEW ENGLAND...COLD/SUB-FREEZING AIR WILL
CONTINUE TO BE REINFORCED IN THE LOW LEVELS FROM THE NE. BUT WARM
AIR ADVECTION CONTINUES ABOVE THE BOUNDARY LAYER...WITH A CHANGEOVER
TO SLEET AND FREEZING RAIN BEGINNING LATE IN THE DAY NEAR THE MARYLAND
BORDER ADJOINING THE LAUREL HIGHLANDS AND SOUTH CENTRAL MOUNTAINS.
THIS WILL BEGIN A PROLONGED PERIOD OF FREEZING PRECIPITATION WITH
POTENTIAL FOR SIGNIFICANT ICE ACCUMS IN THE SOUTHWEST...AND LIGHTER
AMOUNTS TO REMAINDER OF CENTRAL PA. THE PRECIP WILL LAST THROUGH THE
OVERNIGHT...BUT QUESTION REMAINS JUST HOW MUCH QPF WE/LL SEE...AS
HEAVIEST PRECIP REMAINS SOUTH OF THE MARYLAND BORDER. MODELS
GENERALLY AGREE ON A TENTH OR TWO ACROSS THE SOUTHERN TIER BY
00Z...WITH ANOTHER TENTH OR TWO FROM 00-06Z -THOUGH THIS MAY BE
OVERDONE AS REGION WILL BE BETWEEN TWO SHORTWAVES AND THIS TIME
FRAME MAY BE A PRECIP MINIMUM. AMOUNTS INCREASE AGAIN AFTER 06Z
DURING PRIME TIME FOR FZRA...THOUGH MODELS STILL SHOWING NOTABLE
DIFFERENCES IN QPF. GFS AND SREF ON THE HIGH END WITH LARGE AREAS
GREATER THAN 0.25 WHILE NAM AND ESPECIALLY ECMWF GIVING MUCH LOWER
TOTALS. EITHER WAY...ANYTHING THAT FALLS WILL BE A WINTRY MIX OR
LIKELY FZRA. SO EARLIER ISSUED WINTER STORM WATCH REMAINS IN EFFECT
FOR PORTIONS OF THE SOUTHERN AND CENTRAL MTNS. LOOKING AHEAD...AT
LEAST PORTIONS OF CURRENT WSW WILL LIKELY TRANSITION TO A WARNING
LATER THIS
EVENING...SURROUNDED BY A WINTER WEATHER ADVISORY.

WARMER AIR EVENTUALLY WINS OUT IN THE LOWER LEVELS AS WELL. TEMPS
GRADUALLY RISE SUNDAY NIGHT...WITH A TRANSITION TO PLAIN RAIN
FROM S TO N EARLY MONDAY. BY 12Z...PRECIP SHOULD ALREADY BE ALL
RAIN IN THE SE.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
TRANSITION FROM WINTRY PRECIP TO PLAIN RAIN SHOULD OCCUR EARLY
MONDAY...WITH LIGHT SHOWERS PERSISTING ON MONDAY AS STRONG JET
BRINGS SOME LARGE SCALE LIFT BUT NO SHORTWAVES TO FOCUS THE
ENERGY.

STRONG UPPER JET WILL SHIFT OFF THE COAST INTO THE MIDDLE
OF THE WEEK. A TRAILING WEAK WAVE MAY BRUSH THE AREA WITH SOME
LIGHT SNOW ON TUESDAY AFTERNOON AND EVENING BEFORE ARCTIC AIR
SURGES INTO THE REGION FOR THE REST OF THE WORK WEEK. NORTHWEST
FLOW ALOFT AND AROUND BUILDING HIGH PRESSURE AT THE SURFACE WILL
BRING LOWS IN THE SINGLE DIGITS AND TEENS FOR THU AND FRI
MORNING...AND HIGHS MAINLY IN THE 20S.

THIS WEEKEND...FLOW TURNS WESTERLY BRINGING GRADUAL MODERATION TO
TEMPERATURES. ANOTHER WAVE OF LOW PRESSURE PROGGED FOR LATER SAT
INTO SUNDAY.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR CONDS EXPECTED FOR THE EASTERN TAF SITES OVERNIGHT AS HIGH
PRESSURE OVER THE MIDWEST BUILDS EAST INTO PENNSYLVANIA. A BKN-OVC
SHIELD OF CIRRUS/CIRROSTRATUS WILL GRADUALLY SPREAD NE AND THICKEN
UP ACROSS THE STATE OVERNIGHT. MVFR DECK OF STRATO CU ASSOCD WITH
NWRLY FLOW IN CLOUD LAYER HAS BANKED ITSELF UP INTO THE
ALLEGHENIES. THESE LOWER CLOUDS WILL LINGER MOST OF THE NIGHT AT
BFD...BUT ARE EXPECTED TO BREAK UP BEFORE/AROUND MIDNIGHT IN AOO
AND UNV - BUT COULD LAST A LITTLE LONGER AT JST WHERE UPSLOPE FLOW
REMAINS THRU THE FIRST HALF OF THE NIGHT. GRADUAL VEER WILL HELP
THEM BREAK OUT AS WELL.

THE WIND WILL LIGHTEN UP THROUGH THE NIGHT AND VEER ALL THE WAY
AROUND TO A NE/E SFC FLOW IN THE MORNING. THE HIGH PRESSURE
FLOATS TO THE EAST A BIT MORE AND COLD AIR DAMMING RESULTS. THIS
COLD AIR WILL BE TRAPPED AT THE SFC/LOW LEVELS THRU MUCH OF THE
DAYLIGHT ON SUNDAY. STRONG UPPER FORCING RIDES OVERHEAD LATE
SUNDAY. BUT WARM ADVECTION SNOW WILL START IN THE MORNING ALONG
THE SRN BORDER AND LIFT QUICKLY N THRU THE AFTN. AFTER A COUPLE OF
HOURS OF LIGHT SNOW...THE PRECIP TURNS TO PL/FZRA IN THE SOUTHERN
TERMINALS. GRADUALLY THE AIR ALOFT WARMS AND LNS/MDT GO TO PLAIN
RAIN BEFORE NIGHTFALL. JST/AOO/UNV WILL LIKELY SEE A SIG IMPACT TO
FLIGHT DUE TO FZRA/PL AFTER INITIAL SNOW BURST. HEY MIGHT NOT SEE
A TURN TO PLAIN RAIN UNTIL LATE SUN NIGHT. CIGS/VISBYS LOWER
QUICKLY DURING THE LATE MORNING AND AFTN FROM N-S AS SN/PL WORK
DOWN FROM ABOVE. WINDS MAY SHOW ENOUGH OF A VEER BY LATE AFTN TO
WARRANT SOME LLWS MENTION...BUT JUST TOO FAR OUT IN TIME TO DO
THAT WITH THIS 00Z PACKAGE.

IFR/LIFR CONDITIONS SHOULD LINGER AT MOST SITES THROUGH THE NIGHT
AND INTO MONDAY MORNING.

OUTLOOK...
MON...WIDESPREAD MVFR/IFR AS CD FRONT PASSES THRU NW-SE.
TUE-THU...NW FLOW. MVFR/IFR SCT -SHSN NW.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY
MORNING FOR PAZ017>019-024>028-033>036-056-063-064.
WINTER WEATHER ADVISORY FROM 1 PM SUNDAY TO 10 AM EST MONDAY
FOR PAZ057>059-065-066.

&&

$$
SYNOPSIS...LAMBERT/GARTNER
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT/RXR
LONG TERM...RXR
AVIATION...DANGELO