Area Forecast Discussion
Issued by NWS State College, PA

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000 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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