-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 051058
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
558 AM EST THU DEC 5 2013

.SYNOPSIS...
A WARM FRONT...EXTENDING FROM THE UPPER GREAT LAKES INTO FAR
WESTERN PENN AND NRN VIRGINIA...WILL LIFT NORTH THROUGH PENNSYLVANIA
TODAY...ACCOMPANIED BY UNSEASONABLY MILD TEMPERATURES.  A COLD FRONT
WILL PUSH SLOWLY SOUTHEAST THROUGH PENNSYLVANIA LATER TODAY AND
TONIGHT...BEFORE BECOMING NEARLY STATIONARY JUST SOUTH OF THE REGION
FRIDAY. A SERIES OF WAVES WILL RIPPLE NORTHEAST ALONG THE NEARLY
STATIONARY FRONTAL BOUNDARY...BRINGING PERIODS OF RAIN TO MOST OF
THE COMMONWEALTH TONIGHT THROUGH THE MIDDAY HOURS FRIDAY. A GRADUAL
CHANGE TO MIXED PRECIPITATION OR SNOW WILL OCCUR ACROSS CENTRAL AND
NORTHWESTERN PENNSYLVANIA FRIDAY AFTERNOON INTO FRIDAY NIGHT AS THE
COLD AIR DEEPENS. HIGH PRESSURE WILL BUILD OVER THE STATE SATURDAY
AND SATURDAY NIGHT. ANOTHER ROUND OF ACTIVE WINTER WEATHER WILL
DEVELOP LATER SUNDAY INTO MONDAY WITH THE LIKELIHOOD OF MIXED
PRECIPITATION.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
STRATUS DECK BLANKETS ALL OF CENTRAL PENN EARLY TODAY...EXCEPT FOR
THE LAUREL HIGHLANDS AND NW MTNS /NEAR AND TO THE WEST OF ROUTE 219/
WHERE A DUAL LAYER OF GENERALLY BKN STRATO AND ALTO CU CLOUDS
CONTINUES.

MOISTENING BLYR...COMBINED WITH LOCALLY ENHANCED UPSLOPE FLOW WILL
YIELD PATCHY DRIZZLE AND FOG THROUGH THE MID MORNING HOURS...MAINLY
ON THE RIDGE TOPS. PATCHY DENSE FOG WILL ALSO BE FOUND ACROSS THE
LOWER SUSQ VALLEY THROUGH THE PRIME MORNING COMMUTE HOURS. SFC
DEWPOINTS IN THE SE REMAIN IN THE MID TO UPPER 40S WITH A SLIM 0-2F
T/TD SPREAD.

TEMPS WILL REMAIN STEADY OR EVEN RISE A DEG OR TWO EARLY TODAY UNDER
THE WIDESPREAD CLOUD COVER AND LLVL WAA.

THE WARM FRONT PUSHES STEADILY NEWD ACROSS THE CWA DURING THE LATE
MORNING AND MIDDAY HOURS AS THE MEAN BLYR FLOW VEERS TO THE SW.
ANOMALOUSLY HIGH PWAT AIR OF AROUND 1.25 INCHES WILL OVERSPREAD THE
ENTIRE REGION THIS AFTERNOON AHEAD OF A COLD FRONT.

LATEST 00-06Z OPER MODELS AND 03Z ENSEMBLE GUIDANCE ARE IN GOOD
AGREEMENT BRINGING THE COLD FRONT WILL INTO FAR NWRN PA SHORTLY
BEFORE 18Z. THE FRONT WILL DRIFT SE TO NEAR THE ALLEGHENY FRONT BY
00Z...BEFORE CROSSING THE SUSQ VALLEY LATE TONIGHT.

AN INITIAL...WEAK SFC WAVE OF LOW PRESSURE RIDING NE ALONG THIS
BOUNDARY AND BRING AN INCREASING PROBABILITY FOR RAIN ACROSS
NWRN...THEN CENTRAL PENN /MAINLY ON THE COOL SIDE OF THE FRONT/
DURING THE MIDDAY AND AFTERNOON HOURS TDY.

THE BROAD SW FLOW ALOFT WILL KEEP THE COLDER AIR INITIALLY VERY
SHALLOW WITH ANY FROZEN /AND PERHAPS SOME PATCHY FREEZING/ PRECIP
CONFINED TO THE FAR NW PART OF THE CWA THROUGH EARLY THIS EVENING.

THE SERN THIRD...TO HALF OF THE CWA WILL SEE MAINLY OVC
SKIES...AND   JUST A FEW TO SEVERAL HUNDREDTHS OF AN INCH OF
RAINFALL THROUGH 00Z. SOME PLACES IN OUR SE CWA WILL ESCAPE WITH NO
MEASURABLE RAINFALL TODAY.

THIS AFTERNOON COULD VERY WELL BE THE MILDEST DAY FOR THE REST OF
THIS YEAR WITH  HIGHS RANGING FROM THE MID 50S ACROSS THE NRN
MTNS...TO THE UPPER LOWER 60S ACROSS MOST OF CENTRAL AND SRN PA.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
INITIAL SFC WAVE ALONG THE SLOW MOVING COLD FRONT WILL TRACK INTO
THE POCONOS/CATSKILL REGION BY MIDNIGHT TONIGHT...HELPING TO TAPER
OFF THE RAIN AND MIXED PRECIP /TEMPORARILY/ DURING THE SECOND HALF
OF TONIGHT.

THIS FIRST ROUND OF QPF /LATE TODAY AND EARLY TONIGHT/ WILL LIKELY
AVERAGE 0.5 TO 0.8 OF AN INCH ACROSS THE NW HALF OF THE STATE
/AROUND ONE INCH OVER PORTIONS OF THE NW/NCENT MTNS/...WHILE LESS
THAN 0.2 OF AN INCH SHOULD FALL IN THE FAR SE.

THE MAIN SFC WAVE DEVELOPS ALONG THE FRONT FRIDAY AFTERNOON ACROSS
THE CENTRAL APPALACHIANS /WITHIN THE THERMALLY DIRECT...RIGHT
ENTRANCE REGION OF A BROAD/STRONG UPPER LEVEL JET IN EXCESS OF 150
KTS/.

A NE/SW RIBBON OF STRONG 850-700 MB FRONTOGENESIS ON THE COLD SIDE
OF THE ANAFRONT WILL MOVE INTO THE REGION LATER FRIDAY AFTERNOON AND
EVENING LEADING TO A PERIOD OF MODERATE RAIN...THEN SOME MIXED
PRECIP IN THE SE...WITH MAINLY WET SNOW OF VARYING INTENSITY ACROSS
THE CENTRAL AND NW MTNS.

ALTHOUGH THE LIKELIHOOD EXISTS FOR UP TO SEVERAL INCHES OF SNOW
/PRIMARILY OVER THE MTNS JUST WEST OF THE I-99/RT 220 CORRIDOR/ THE
EXACT LOCATION...TIMING...AND AMT IS STILL A LITTLE UNCERTAIN. PER
COORDINATION WITH NEIGHBORING WFOS TO OUR WEST AND NORTH...WE
DECIDED TO HOLD OFF ON ANY WINTER WEATHER ADVISORIES AT THIS EARLY
POINT IN TIME.

FCST LEQ TOTALS /FROM THE TWO SEPARATE WAVES IN THE 00Z FRI-12Z SAT
TIMEFRAME/ SHOULD BE BTWN 1-2 INCHES ACRS THE CWA - BASED ON THE
LATEST 00-06Z IN-HOUSE CONSENSUS BLENDED QPF.

DEEPENING COLD AIR WILL ADVECT INTO THE STATE BY 12Z SAT WITH
LINGERING LIGHT SNOW/MIXED PRECIP IN THE EAST...AND JUST SOME
FLURRIES ELSEWHERE AS THE STRONG COLD FRONT REACHES THE EAST COAST.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
HIGH PRESSURE OVER THE UPPER MIDWEST SATURDAY WILL BUILD EAST OVER
THE STATE SATURDAY NIGHT...BEFORE BECOMING CENTERED/RETREATING TO
THE NEW ENGLAND STATES BY LATE SUNDAY.

THE ACTIVE WINTER PATTERN DEVELOPS AGAIN BY LATE SUNDAY INTO EARLY
NEXT WEEK WITH ANOTHER POTENTIAL SIGNIFICANT OVERRUNNING MIXED
WINTRY PCPN EVENT SLATED FOR SUN-MON. A CONSENSUS OF MEDIUM RANGE
MODEL AND ENSEMBLE GUIDANCE SHOWS LOW PRES DEVELOPING OVR THE LWR
MS/TN VLY AND LIFTING NWD ALONG THE WEST-SIDE OF THE APPLCHNS THRU
THE OH VLY/GRT LKS. A SURGE OF ABOVE NORMAL PWATS WILL SPREAD NEWD
FROM THE GOMEX BEHIND A BROAD SWLY FLOW ALOFT AND OVERRUN A
RETREATING COLD SECTOR AIRMASS ASSOCIATED WITH A MODIFIED ARCTIC SFC
HIGH MIGRATING EWD FROM THE UPPER MIDWEST INTO SRN QUEBEC AND NRN
NEW ENGLAND. THE SYNOPTIC PATTERN LOOKS VERY CONDUCIVE FOR A
POTENTIAL SIGNIFICANT FREEZING/FROZEN PCPN EVENT AS THE DEEP MSTR
AND AND STG WAA ALOFT FLOWS OVER THE TOP OF A SHALLOW SUB-FZG
AIRMASS THAT COULD BE ENTRENCHED /VIA COLD AIR DAMMING/ E OF THE
ALLEGHENIES FOR A PROLONGED PERIOD OF TIME. BASED ON THE EVOLVING
TRENDS IN THE GUIDANCE...INCREASED POPS INTO THE HIGH LKLY RANGE FOR
DAYS 5-6. WILL CONTINUE TO HIGHLIGHT WINTER STORM POTENTIAL IN THE
HWO.

IN THE WAKE OF THIS SYSTEM...A VERY COLD NW FLOW SHOULD GRIP THE
REGION WITH WELL BELOW NORMAL TEMPS AND POSSIBLE LAKE EFFECT
SNOWS OVER THE NW MTNS.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
CURRENT INFARED SHOWS MID TO HIGH CLOUD OVERSPREADING THE REGION
WITH CLEARING THROUGH THE EAST. THE CLOUDS TO THE WEST AND THE FOG
TO THE EAST HAS ALLOWED WIDESPREAD MVFR TO IFR VISIBILITIES OVER
THE REGION OVERNIGHT. AT THE EASTERN TAF SITES...LNS...MDT AND IPT
EXPECT IFR AND LOWER CIGS AND VSBYS TO CONTINUE THROUGH 16Z ALONG
THE LOWER SUSQ.

AFTER SUNRISE...CONDITIONS WILL RECOVER TO MVFR AT MOST
TERMINALS...BY LATE MORNING...POSSIBLY EVEN VFR BY LATE AFTERNOON AS
MIXING INCREASES THANKS TO WINDS AHEAD OF APPROACHING COLD FRONT.
WORST CONDITIONS WILL HANG IN LONGEST OVER THE HIGH TERRAIN OF THE
WEST AND NORTH...WHILE THE BEST CHANCE FOR UNLIMITED CIG/VIZ TO
DEVELOP WILL BE OVER THE SE.

RAIN AND DETERIORATING CONDITIONS WILL MOVE IN ONCE AGAIN FROM
THE WEST LATE IN THE AFTERNOON THURSDAY AHEAD OF THE FRONT AND
WILL CONTINUE TONIGHT INTO FRIDAY.

WITH THE STRONG FRONT MOVING IN...WINDS OUT AHED OF THE FRONT
COULD BE STRONG ENOUGH TO ALLOW FOR LLWS. HAVE CURRENTLY LEFT IT
OUT OF THE TAFS AS IT IS MARGINAL...BUT POSSIBILE. IF IT ODOES
OCCUR IT WOULD BE OUT OF THE SOUTHWEST AT 35 KTS.

OUTLOOK...

FRI...MVFR IN RAIN SE. IFR IN SNOW/WINTRY MIX NW.

SAT...NO SIG WX.

SUN...REDUCTIONS DEVELOPING FROM MVFR TO IFR. SNOW THEN WINTRY MIX
LIKELY SPREADING S TO N SUN INTO SUN NIGHT.

MON...WIDESPREAD MVFR/IFR ASSOCIATED WITH A PASSING COLD FRONT.
-- End Changed Discussion --

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...FITZGERALD/LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT/STEINBUGL
LONG TERM...LAMBERT/STEINBUGL
AVIATION...CERU/GARTNER