Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 241522
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1022 AM EST WED DEC 24 2014

.SYNOPSIS...

AN INTENSIFYING STORM SYSTEM OVER THE LOWER OHIO RIVER VALLEY THIS
MORNING WILL MOVE THROUGH THE EASTERN GREAT LAKES THIS
EVENING...DRAGGING A COLD FRONT THROUGH THE REGION OVERNIGHT.
GUSTY WEST WINDS WILL DEVELOP BEHIND THE FRONT LATE TONIGHT AND
THURSDAY. ANOTHER LESS POTENT COLD FRONT WILL MOVE ACROSS THE AREA
THIS WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

REGIONAL RADAR SHOWS A LARGE SHIELD OF RAIN EXTENDING ALL WAY DOWN
INTO THE CAROLINAS LEADING TO A HIGH CONFIDENCE FORECAST OF A
DREARY CHRISTMAS EVE WITH PERIODS OF RAIN AND AREAS OF FOG.

SHORT RANGE GUIDANCE FAVORS MY CENTRAL AND EASTERN ZONES FOR THE
BEST CHANCE OF THE STEADIEST RAINS...WHILE WESTERN AREAS WILL
LIKELY SEE MORE IN THE WAY OF RAIN AND MIST WITH PERIODS OF NOT
MUCH AT ALL HAPPENING INTO THE EVENING.

INCREASINGLY STRONG SOUTHERLY LOW LEVEL FLOW WILL ADVECT ABUNDANT
MOISTURE INTO THE REGION LEADING TO LIGHT TO MODERATE RAIN. PWATS
INCREASING TO BETWEEN 4-5 ST DEV ABOVE NORMAL THIS MORNING WILL
HELP BRING WIDESPREAD 0.5 TO 0.75 INCH AMOUNTS OF RAIN ACROSS
MOST OF CENTRAL AND EASTERN PA. THE RAIN COULD FALL HEAVY AT
TIMES NEAR AND TO THE EAST OF THE I-81 CORRIDOR...WHERE TOTALS OF
1-1.3 INCHES ARE LIKELY BY THIS EVENING.

TEMPS THROUGH THE MID MORNING WILL BE IN THE LOWER TO MID 40S IN
MOST LOCATIONS WITH A GENERALLY LIGHT WIND FROM THE EAST TO
SOUTHEAST...BUT GUSTS AROUND 20 MPH WILL BE LIKELY ON THE HIGHER
TERRAIN...AND INVOF KIPT WHERE CHANNELING EFFECTS OF THE EAST/WEST
VALLEY WILL ACCENTUATE SPEEDS.

HIGH TEMPS LATE THIS AFTERNOON WILL VARY FROM THE MID 40S ACROSS
THE NRN MTNS...TO THE MID-UPPER 50S ACROSS THE LOWER SUSQ VALLEY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
HI RES MODELS INDICATING LIKELY A SQUALL LINE TO ACCOMPANY SFC
COLD FRONT...THAT WILL BE LAGGING THE UPPER FRONTAL PASSAGE THIS
EVENING. EXTENT OF SURFACE DESTABILIZATION WILL ULTIMATELY
DETERMINE HOW STRONG THIS SQUALL LINE CAN GET/STAY AS IT MOVES
INTO THE WESTERN THIRD OF OUR CWA BETWEEN 01-04Z THURSDAY.

AS NOTED BY PREVIOUS SHIFTS...THIS IS EASILY ONE OF THE BETTER
SEVERE WEATHER SETUPS FOR CHRISTMAS EVE /AT LEAST ACROSS THE WRN
MTNS...WHERE UP TO A FEW HUNDRED J/KG OF MU/ML CAPE IS FCST TO
DEVELOP THIS EVENING/. THE POTENTIAL EXISTS FOR SCTD WIND GUSTS
OF 40-45 KTS WITHIN THE ANTICIPATED NCFRB.

EVEN MINIMAL CAPE COMBINED WITH STRONG /DEEP-LAYER WIND FIELDS A
FEW TO SVRL KFT AGL OFTEN RESULTS IN A NCFRB WITH LOCALIZED
DOWNBURST DAMAGE OCCURRING BENEATH MINI BOWS IN THE LINE. SPC HAS
PLACED MUCH OF CENTRAL PA IN MARGINAL CATEGORY FOR DAY 2 AS A
RESULT. MORE DETAILS BELOW.

THE ALREADY MILD TEMPS LATE THIS AFTERNOON...WILL CLIMB UP TO
SEVERAL DEG F...INTO THE U40S TO U50S TONIGHT...AS STRONGER
SOUTHERLY WINDS DEVELOP AT THE SFC AND ALOFT. THE WARMEST
READINGS OVR MUCH OF THE AREA MAY NOT BE REACHED UNTIL AFTER DARK
THIS EVENING.

GUSTY WESTERLY WINDS /BETWEEN 35 AND 45 MPH/ AND SCTD...MAINLY
MTN SNOW SHOWERS WILL BE THE FEATURED CONDITIONS FOR CHRISTMAS
DAY.

TEMPS WILL BE STEADY OR SLOWLY FALLING FOR MUCH OF THE DAY
THURSDAY...AFTER THE INITIAL DROP OF 10F OR SO IMMEDIATELY
FOLLOWING THE CFROPA VERY EARLY ON.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
MORE TRANQUIL WEATHER DEVELOPING FOR THURSDAY NIGHT AND FRIDAY...
WITH SW FLOW.

DID UP TEMPS FRIDAY INTO SAT...GIVEN RISING HEIGHTS.

CUT BACK PCPN FOR LATE FRIDAY.

12Z EC RUN HAS SYSTEM FURTHER NW NOW...BUT FOR NOW WENT WITH
SLIGHT CHC OF SNOW FROM SUNDAY INTO EARLY MONDAY MORNING.

AGAIN WITH SPLIT FLOW...THERE COULD BE SOME CHANCE FOR A SOUTHERN
WAVE TO BRING SOME RAIN OR SNOW SHOWERS TO THE AREA AT TIMES...BUT
IT LOOKS LIKE ANYTHING WOULD BE FAST MOVING. PERHAPS A CHANGE
LATER NEXT WEEK...AS CROSS POLAR FLOW SETS UP.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
WIDESPREAD REDUCTIONS IN PLACE THIS MORNING /WITH MOST TERMINALS
REPORTING IFR CONDITIONS AT 12Z/ WILL CONTINUE THROUGH THE DAY AS
AN INTENSIFYING STORM SYSTEM OVER THE LOWER OHIO RIVER VALLEY
MOVES NNE ACROSS THE GREAT LAKES PUSHING A PLUME OF UNSEASONABLY
MOIST AIR INTO AN ALREADY MOIST AIRMASS OVER PA. AN AREA OF RAIN
WILL ALSO IMPACT MUCH OF THE CWA TODAY.

THE ASSOCIATED TRAILING COLD FRONT WILL PUSH THROUGH CENTRAL
PENNSYLVANIA TONIGHT. STRONG AND GUSTY WEST WINDS WILL OCCUR
BEHIND THE FRONT TONIGHT AND THURSDAY.

INCLUDED LLWS FOR ALL TAF SITES INITIALLY THIS MORNING AS WINDS
ALOFT BEING TO INCREASE AHEAD OFF APPROACHING FRONTAL SYSTEM OVER
THE MIDWEST WHILE SFC WINDS REMAIN SERLY. ANOTHER BOUT OF LLWS
MOVES IN TONIGHT WITH STRONG WESTERLY FLOW BEHIND COLD FRONT.

OUTLOOK...

THU...WINDY AND COLDER WITH SCT MVFR CIGS AND -SHSN. LLWS.

FRI...FAIR AND MOSTLY VFR.

SAT...FAIR AND MOSTLY VFR. SCT SHSN WITH LOCAL REDUCTIONS NW.

SUN...MVFR TO IFR WITH CHC RA/SN...ESP SOUTH.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 8 PM THIS EVENING TO NOON EST THURSDAY FOR
PAZ004>006-010>012-017-018-024-033.

&&

$$
SYNOPSIS...LA CORTE/LAMBERT
NEAR TERM...LA CORTE/LAMBERT
SHORT TERM...LAMBERT
LONG TERM...LAMBERT/MARTIN
AVIATION...RXR



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