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000
FXUS61 KCTP 052235
AFDCTP

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

.SYNOPSIS...
A SERIES OF LOW PRESSURE WAVES WILL TRACK NORTHEAST FROM THE
TENNESSEE VALLEY ACROSS THE MID-ATLANTIC STATES TONIGHT THROUGH
FRIDAY...BRINGING PERIODS OF MIXED PRECIPITATION TO THE AREA. HIGH
PRESSURE WILL PROVIDE A BRIEF RESPITE IN THE RECENTLY ACTIVE EARLY
SEASON WINTER WEATHER PATTERN ON SATURDAY. CONFIDENCE IS STEADILY
INCREASING FOR A PERIOD OF FROZEN AND FREEZING PRECIPITATION
SUNDAY INTO EARLY MONDAY THAT SHOULD EVENTUALLY CHANGE TO RAIN. AN
ARCTIC FRONTAL PASSAGE EARLY NEXT WEEK WILL DROP TEMPERATURES WELL
BELOW NORMAL THROUGH NEXT WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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AT 22Z...COLD FRONT LOCATED JUST W OF KBFD AND KPIT. AHEAD OF
CDFRONT...A BAND OF SHOWERS IS FALLING ACROSS THE CENTRAL COUNTIES ALONG
AXIS OF LL JET/ANOMALOUS PWATS. SHORT RANGE OPERATIONAL MODELS
AGREE IN TRACKING COLD FRONT SE ACROSS THE AREA OVERNIGHT. COLD
FRONT AND WEAK WAVE ALONG IT WILL CLEAR SE PA BY DAWN...RESULTING
IN THE STEADIEST PRECIP TAPERING OFF LATE TONIGHT. THERE WILL BE A
RACE BETWEEN THE COLDER AIR WANTING TO FILTER IN FROM THE GRT LKS
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 LIQUID QPF 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.
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&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
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ANOTHER WAVE IS EXPECTED TO FORM ALONG THE BOUNDARY SOUTH OF PA
FRIDAY WITH ANOTHER SLUG OF PRECIP FOR FRIDAY AFTERNOON AND
EVENING. STRONG FRONTOGENETIC FORCING WILL DEVELOP UNDER THE
ENTRANCE REGION OF A VERY STRONG JET STREAK THAT WILL RACE DOWN
THE ST LAWRENCE RIVER VALLEY. THE BIGGEST ISSUE WITH THE SECOND
WAVE WILL BE THE AMOUNT OF WINTRY WEATHER ASSOCIATED. COLDER AIR
WILL BE RETURNING QUICKLY...ESPECIALLY IN THE AFTERNOON AS THE
HEAVIEST PRECIP WILL BE OCCURRING. THE PRECIP TYPES WILL BE
COMPLICATED AND CHANGING AS THE EVENT EVOLVES...BUT AT THIS POINT
WE FEEL THAT THE FAR NW WILL PROBABLY BE MAINLY SNOW...RAIN
TRANSITIONING THROUGH MIXED PRECIP THEN ENDING AS SNOW ACROSS THE
CENTRAL COUNTIES...AND MAINLY RAIN OVER ABOUT THE SERN 1/3 OR SO
OF MY FCST AREA.

THINKING IS FOR A GENERAL 1-4 INCH SNOWFALL OVER MY NWRN ZONES
WITH JUST ENUF ICE MIXED IN OVER SOUTH-CENTRAL AND LAUREL HIGHLAND
AREAS TO MAKE FOR A SLIPPERY COMMUTE. HAVE PUT AN ADVISORY UP FOR
THE SNOW-SLEET-FREEZING RAIN POTENTIAL LASTING INTO LATE FRIDAY
NIGHT.

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

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
1040+ MB MODIFIED ARCTIC SFC HIGH PRESSURE OVER THE UPPER MIDWEST
SATURDAY WILL MIGRATE EASTWARD INTO THE NORTHERN MID-ATLANTIC
STATES BY SUNDAY MORNING...SETTING THE STAGE FOR WHAT APPEARS TO
BE A CLASSIC OVERRUNNING MIXED PRECIP EVENT FOR LATER SUNDAY INTO
MONDAY.

05/12Z DETERMINISTIC MODEL AND ENSEMBLE GUIDANCE SHOWS LOW PRES
INITIALLY DEVELOPING ALONG AN INVERTED SFC TROUGH AXIS EXTENDING
FROM THE LWR MS/TN VLY NEWD UP THE WEST-SIDE OF THE APPALACHIANS.
THE MAIN LOW SHOULD LIFT NWD THRU THE OH VLY/GRT LKS INTO SERN
CANADA ON DAYS 5-6. MEANWHILE A SECONDARY/WEAKER AREA OF LOW PRES
SHOULD FORM NEAR THE VA/NC COAST AND TRACK NNEWD JUST OFFSHORE SRN
NEW ENGLAND.

DOWNSTREAM FROM A VIGOROUS MID/UPPER LEVEL TROUGH DIGGING THROUGH
THE FOUR CORNERS/SRN ROCKIES...A SURGE OF INTENSE 850-700MB WARM
AIR/THETA E/MOISTURE ADVECTION WILL SPREAD QUICKLY NEWD BEHIND A
BROAD SWLY FLOW ALOFT AND OVERRUN A RETREATING COLD SECTOR
ASSOCIATED WITH THE RETREATING ARCTIC HIGH. THE SYNOPTIC PATTERN
LOOKS VERY CONDUCIVE FOR A PERIOD OF FREEZING-TO-FROZEN PCPN AS
MSTR AND STG WAA ALOFT FLOWS OVER THE TOP OF A SHALLOW SUB-FZG
AIRMASS THAT SHOULD REMAIN ENTRENCHED ALONG/E OF THE ALLEGHENIES
VIA LLVL COLD AIR DAMMING/SFC PRES CHANNELING...ENHANCED BY NELY
AGEO FLOW AND WET BULB EFFECTS. SFC-850MB TEMPS ARE FCST TO WARM
ENOUGH TO CHANGE FREEZING PTYPES TO PLAIN RAIN IN MOST AREAS
AROUND MON AFTN BEFORE THE ARCTIC COLD FRONT CROSSES THE REGION
MON NGT. THE 12Z GEFS MEAN SHOWS A HIGH PROBABILITY OF A FEW
INCHES OF SNOW/SLEET ON THE LEADING EDGE OF THE PRECIP SHIELD
FOLLOWED BY POTENTIAL SIGNIFICANT ICE ACCUMS ESPECIALLY FROM THE
LAURELS/SCNTRL MTNS INTO THE INTERIOR N-CNTRL PART OF THE CWA.
WILL CONTINUE TO HIGHLIGHT THIS SYSTEM IN THE HWO BUT CONFIDENCE
IS INCREASING IN AT LEAST AN ADVISORY TYPE EVENT...IF NOT WARNING
ASSUMING MOD-HVY ICING VIA FZRA.

IN THE WAKE OF THIS SYSTEM...A VERY COLD PATTERN SHOULD GRIP THE
REGION THRU THE MIDDLE OF NEXT WEEK WITH TEMPERATURES WELL BELOW
NORMAL. SOME LAKE EFFECT SNOW SHOWERS ARE POSSIBLE IN THE COLD
CYC FLOW ALOFT ALTHOUGH THE LLVL WINDS MAY HAVE TOO MUCH OF A SW
COMPNT WHICH WOULD ORIENT BANDS MORE ALONG THE LAKE ERIE SHORE
INTO SW NY.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
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
NEAR TERM...FITZGERALD/LA CORTE
SHORT TERM...LA CORTE/STEINBUGL
LONG TERM...STEINBUGL
AVIATION...LA CORTE/COLBERT