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000
FXUS61 KCTP 051718
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1218 PM EST THU DEC 5 2013

.SYNOPSIS...
A COLD FRONT WILL SAG THROUGH THE AREA LATER TODAY AND THIS
EVENING...BECOMING STATIONARY JUST SOUTH OF PENNSYLVANIA TONIGHT
AND FRIDAY. A SERIES OF WAVES WILL RIPPLE NORTHEAST ALONG THE
NEARLY STATIONARY FRONTAL BOUNDARY FOLLOWED BY HIGH PRESSURE FOR
SATURDAY INTO SATURDAY NIGHT. A NEW WINTER STORM WILL MOVE INTO
THE AREA SUNDAY INTO MONDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WIDESPREAD CLOUDINESS AND UNSEASONABLY MILD TEMPS BLANKET THE
REGION...WITH LOCALLY DENSE FOG THROWN IN FOR GOOD MEASURE OVER THE
LOWER SUSQ VALLEY. TO MAKE THINGS REALLY INTERESTING...THE LEADING
EDGE OF THE RAIN MOVING INTO SW PA HAS THUNDERSTORMS EMBEDDED IN
IT. NOT YOUR TYPICAL EARLY DECEMBER DAY FOR SURE.

THE REST OF THE DAY WILL FEATURE INCREASED CHANCES FOR RAIN MOVING
IN FROM THE WEST...WITH THE LOWEST CHANCES FOR RAIN OVER MY FAR
SERN COUNTIES. MARGINAL INSTABILITY COULD ALLOW FOR A FEW RUMBLES
OF THUNDER OVER THE SOUTHERN TIER...BUT BASICALLY WE ARE IN FOR
ANOTHER DRAB DAY WITH PERIODS OF RAIN DEVELOPING AS THE COLD FRONT
ENTERS THE REGION.

THIS AFTERNOON COULD VERY WELL BE THE MILDEST DAY WE WILL SEE 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/...
SHORT RANGE OPERATIONAL MODELS AGREE IN FORMING A WAVE ALONG THE
COLD FRONT AND RIPPLING IT OVER MY SERN ZONES LATER TODAY AND
TONIGHT...ALLOWING THE STEADIEST PRECIP TO TAPER OFF. THERE WILL
BE A RACE BETWEEN THE COLDER AIR WANTING TO FILTER IN FROM THE GR
LAKES AND THE RAIN WANTING TO EXIT OFF TO THE EAST. AT THIS POINT
IT LOOKS LIKE THERE WILL BE A BRIEF MIX OR CHANGEOVER TO SNOW ON
THE BACK EDGE OF THE PRECIP THAT COULD BRING A COATING OF SNOW BY
MORNING...MAINLY TO HIGHER ELEVATIONS OF THE N-NW. THERE ARE NO
INDICATIONS OF HAVING ENOUGH QPF IN THE COLD AIR TO SUPPORT MUCH
MORE THAN NUISANCE AMOUNTS...BUT TRAVEL COULD GET SLIPPERY.

THIS FIRST ROUND OF QPF LATE TODAY AND EARLY TONIGHT WILL LIKELY
AVERAGE 3/4 TO 1 INCH ACROSS MUCH OF MY CWA...WHILE LESS THAN 1/2
INCH SHOULD FALL IN THE FAR SE.

     FROM EARLIER DISCUSSION...

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 THURSDAY/...
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 /17Z THURSDAY THROUGH MONDAY/...
REGIONAL ANALYSIS CONTINUES TO SHOW WIDESPREAD MVFR/IFR
CONDITIONS DUE TO RAIN AND LOW CIGS...WITH LIFR OVER THE LOWER
SUSQ TERMINALS WHERE FOG IS STILL LOCALLY DENSE. IMPROVEMENT WILL
BE PAINFULLY SLOW TODAY...WITH CURRENT FLYING CONDITIONS ONLY
HOPING TO IMPROVE TO MVFR AT BEST AS RAIN ASSOCIATED WITH THE
FRONT MOVES INTO THE REGION.

MVFR AND LOWER FLIGHT CATEGORIES WILL CONTINUE INTO FRIDAY AS MORE
RAIN...SNOW...AND WINTRY MIX OVERSPREAD THE REGION.

OUTLOOK...

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

SAT...MVFR SNOW SHOWERS IN THE MOUNTAINS. VFR IN CENTRAL/EASTERN
AREAS.

SUN...REDUCTIONS DEVELOPING WITH APPROACHING STORM THAT WILL BRING
A WINTRY MIX SPREADING SOUTH TO NORTH INTO SUN NIGHT.

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

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 1 PM FRIDAY TO 5 AM EST SATURDAY
FOR PAZ004>006-010>012-017-018-024-033-037-041-042.

&&

$$
SYNOPSIS...LA CORTE/LAMBERT
NEAR TERM...LA CORTE/LAMBERT
SHORT TERM...LAMBERT/STEINBUGL
LONG TERM...LAMBERT/STEINBUGL
AVIATION...LA CORTE/COLBERT