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000
FXUS61 KCTP 072228
AFDCTP

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

.SYNOPSIS...
HIGH PRESSURE WILL MOVE EAST ACROSS PENNSYLVANIA THROUGH
TONIGHT...PROVIDING A BRIEF RESPITE FROM THE ACTIVE EARLY SEASON
WINTER WEATHER PATTERN. ANOTHER PERIOD OF FROZEN AND FREEZING
PRECIPITATION WILL ARRIVE SUNDAY AND CONTINUE INTO EARLY MONDAY.
AN ARCTIC FRONTAL PASSAGE EARLY NEXT WEEK WILL DROP TEMPERATURES
WELL BELOW NORMAL THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
SFC HIGH NOW CENTERED OVER THE DAKOTAS WILL CONTINUE TO BUILD
EAST OVER THE NEXT TWENTY FOUR HOURS...BECOMING CENTERED OVER
CENTRAL PA BY SUNDAY MORNING. THIS MAKE FOR FOR A CLEAR AND COLD
NIGHT ACROSS CENTRAL PA AND THE CALM BEFORE THE NEXT EARLY WINTER
STORM. LOW TEMPS WILL BE IN LOW TEENS ACROSS THE NORTHERN TIER
COUNTIES WITH A FEW SINGLE DIGITS THROWN IN FOR GOOD MEASURE IN THE
COLDER VALLEYS ESP WITH NEW SNOW ON THE GROUND....TO THE LOWER 20S
ACROSS THE LOWE SUSQ VALLEY/HARRISBURG METRO AREA.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
COLD AIR DAMMING ASSOCIATED WITH DEPARTING EAST COAST SFC RIDGE
AXIS WILL BE OVERRUN BY A PERSISTENT SOUTHWEST UPPER FLOW WITH
INCREASING JET SPEEDS AND EMBEDDED WEAK SYSTEMS SUNDAY INTO SUNDAY
NIGHT...BRINGING A BOUT OF WINTRY WEATHER TO THE REGION.

COMPLEX QPF FORECAST FOR THIS OVERRUNNING EVENT WILL KEEP FORECAST
ON THE TRICKY SIDE. 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 POSS ALONG THE MASON/DIXON LINE. HIGHS WILL
BE IN THE UPPER 20S TO LOWER 30S.

AS HIGH RETREATS INTO NEW ENGLAND...COOL 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 WILL BEGIN 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.

&&

.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 /22Z SATURDAY THROUGH THURSDAY/...
VFR CONDS AT MOST TAF SITES WILL CONTINUE OVERNIGHT AS HIGH PRESSURE
OVER THE MIDWEST BUILDS EAST INTO PENNSYLVANIA. A BKN-OVC SHIELD OF
CIRRUS/CIRROSTRATUS WILL GRADUALLY SPREAD NE AND THICKENING UP
ACROSS THE STATE OVERNIGHT.

THE LONE TROUBLE SPOT WILL BE ACROSS FAR NWRN PENN. MVFR CONDS WILL
CONTINUE AT KBFD AS A LIGHT NWRLY...LLVL FLOW TRANSPORTS MOISTURE
FROM LAKE ERIE INLAND AND UPSLOPE OVER THE AIRFIELD. THIS BKN-OVC
DECK OF STRATO CU CLOUDS SHOULD PERSIST THROUGH MUCH OF THE NIGHT.

THE NORTHWEST BREEZE OF 5-10 KTS THIS EVENING WILL VEER ALL THE
WAY AROUND TO LIGHT EASTERLY LATE TONIGHT AND EARLY SUNDAY
MORNING...BEFORE INCREASING FROM THE ESE DURING THE DAY SUNDAY AS
CLOUDS LOWER/THICKEN-UP FROM SOUTH TO NORTH.

LOW PRESSURE IS FORECAST TO TRACK UP THE APPALACHIANS SUNDAY INTO
MONDAY PRODUCING ANOTHER ROUND OF MIXED WINTRY PCPN...BASICALLY SNOW
CHANGING TO ICE SUNDAY NIGHT...THEN TO RAIN ON MONDAY.

MVFR CONDITIONS IN LIGHT SNOW WILL BEGIN ACROSS SOUTHERN PENN DURING
THE LATE MORNING AND ADVANCE NORTH TO AROUND INTERSTATE 80 DURING
THE EARLY TO MID AFTERNOON HOURS.

OUTLOOK...

MON...WIDESPREAD MVFR/IFR ASSOCIATED WITH A PASSING COLD FRONT.

TUE-WED...WEST TO NORTHWEST FLOW DEVELOPING. COLD WITH SCT -SHSN
NORTH AND WEST.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY
MORNING FOR PAZ017>019-024>028-033>036-056-063>065.

&&

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