Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 242049 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 349 PM EST WED DEC 24 2014 .SYNOPSIS... AN INTENSIFYING STORM SYSTEM OVER WESTERN OHIO WILL MOVE UP 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 AM THURSDAY MORNING/... REGIONAL RADAR SHOWS A LARGE-DISORGANIZED SHIELD OF RAIN EXTENDING ALL WAY DOWN INTO THE CAROLINAS. THE MAIN THRUST REMAINS OFF TO THE NORTHEAST WITH THE LATEST HRRR SUGGESTING THE BEST CHANCES FOR RAIN INTO THE EVENING BEING FROM CENTRAL PA EASTWARD...WITH MORE IN THE WAY OF A SPOTTY LIGHT RAIN OR SHOWERS EXPECTED OVER MY WESTERN ZONES. NOT MUCH REASON TO EXPECT OTHER THAN A CONTINUATION OF A DREARY CHRISTMAS EVE WITH PERIODS OF RAIN AND AREAS OF FOG. THE COLD FRONT SHOULD BE ENTERING MY WESTERN ZONES BETWEEN ABOUT 6 AND 9 PM...AND THEN IS EXPECTED TO SPEED ACROSS THE FORECAST AREA TO BE EXITING MY FAR EASTERN ZONES BY THE PRE DAWN HOURS OF CHRISTMAS MORNING. THE FRONT WILL BE ACCOMPANIED BY SOME MARGINALLY STEEP MID LEVEL LAPSE RATES WHICH COULD LEAD TO A RUMBLE OR TWO OF THUNDER ACCOMPANYING THE SYSTEM AS IT RACES THROUGH. EARLIER EXPECTATIONS OF SOME SORT OF NARROW COLD FRONTAL RAIN BAND-SQUALL LINE FEATURE IS BEING DOWNPLAYED IN THE LATEST HIGH RES MODEL GUIDANCE WHICH SHOWS A GENERAL AREA OF SHOWERS MOVING ACROSS THE REGION THIS EVENING ALONG AND AHEAD OF THE FRONT. THIS SHOULD DIMINISH THE THREAT OF STRONG WINDS ALOFT BEING TRANSFERRED DOWN IN THE CONVECTION. TEMPS WILL STAY STEADY OR EVEN CLIMB AS THE FRONT ENTERS THE REGION THIS EVENING HELPING MIX UP THE COOL AIR DAMMED BOUNDARY LAYER. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... CHRISTMAS DAY WILL BRING A TRANSITION INTO A PRETTY TYPICAL POST FRONTAL COOL SEASON PATTERN...WITH CLOUDS AND BLUSTERY GUSTY WESTERLY WINDS. HIGHER ELEVATIONS WILL LIKELY SEE WINDS AS HIGH AS 35-45 MPH...WITH THE REST OF US MAINLY EXPERIENCING WINDS IN THE 20-30 MPH RANGE. THE USUAL SCATTERED MAINLY HIGHER ELEVATION SNOW SHOWERS WILL BE THE FEATURED CONDITIONS...WITH THE CENTRAL RIDGE-VALLEY REGION SEEING LITTLE MORE THAN A PASSING LIGHT RAIN OR SNOW SHOWER. THE POST FRONTAL AIR IS NOT REALLY VERY COLD SO EVEN WHERE THE MAIN PRECIPITATION TYPE IS EXPECTED TO BE SNOW...TEMPERATURES ABOVE FREEZING WILL KEEP ANY ACCUMULATIONS ON THE INSIGNIFICANT SIDE. 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 WEDNESDAY/... POTENT LONGWAVE UPPER TROF EXITING THE EAST COAST AT THE START OF THE PERIOD WILL BE REPLACED BY UPPER RIDGING INTO THE WEEKEND. AS LONGWAVE UPPER TROFFING IS FORECAST TO DEVELOP OVER THE WRN US STARTING EARLY IN THE PD AND NRN STREAM ENERGY RETREATS INTO EASTERN CANADA...MDT TO STRONG SWRLY FLOW ALOFT IS THEN FORECAST TO DOMINATE THE EASTERN CONUS FROM LATE IN THE WEEKEND THROUGH THE REMAINDER OF THE YEAR. MEDIUM RANGE GUIDANCE IS FAIRLY CONSISTENT ESPECIALLY EARLY IN THE PERIOD...BUT THEN SOME DIFFERENCES ARISE IN 500MB FLOW PATTERN AFTER MONDAY AS THE ECMWF MOVES ENERGY EAST FASTER...WHILE THE GFS CLOSES OFF AN UPPER LOW OVER THE DESERT SW. A NORTHERN STREAM WAVE IS FORECAST TO SUPPORT A COLD FRONT MOVING EAST ACROSS THE STATE LATE IN THE WEEKEND...POSSIBLY STALLING NEAR THE MASON DIXON LINE INTO MONDAY AS IT ENCOUNTERS RESISTANCE FROM THE BUILDING UPPER FLOW. THIS FRONT LOOKS TO BE THE MAIN FOCUS FOR PCPN IN THE LONG TERM PERIOD. WITH SNOW TO THE NORTH AND WEST...AND A MIX TO RAIN ACROSS THE SOUTH. WITH RIDGING OR SWRLY FLOW ALOFT MUCH OF THE PERIOD WILL FEATURE ABOVE NORMAL TEMPS...WITH A COOL DOWN TOWARD NORMAL BY NEW YEARS EVE. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... WIDESPREAD MVFR/IFR WITH RAIN AND AREAS OF FOG WILL CONTINUE INTO THE EVENING AS A STORM SYSTEM MOVES INTO THE EASTERN GREAT LAKES THIS EVENING. THE ASSOCIATED TRAILING COLD FRONT WILL PUSH THROUGH CENTRAL PENNSYLVANIA TONIGHT. ISOLATED EMBEDDED THUNDERSTORMS CANNOT BE RULED OUT ALONG THE FRONT. STRONG AND GUSTY WEST WINDS WILL DEVELOP BEHIND THE FRONT TONIGHT AND THURSDAY. INCLUDED LLWS FOR ALL TAF SITES AS WINDS ALOFT BEGIN TO INCREASE AHEAD OF THE APPROACHING FRONTAL SYSTEM WHILE SFC WINDS REMAIN RELATIVELY LIGHT OUT OF THE SE. WESTERN HIGH TERRAIN TERMINALS WILL HOLD ONTO REDUCED CONDITIONS THROUGH MUCH OF CHRISTMAS DAY AFTER WINDS SHIFT TO THE WEST BEHIND THE COLD FRONT...WHILE CENTRAL AND EASTERN TERMINALS WILL SEE CEILINGS IMPROVE TO THE 3000-5000` RANGE BY LATE TONIGHT OR FAIRLY EARLY CHRISTMAS MORNING. OUTLOOK... FRI...FAIR AND MOSTLY VFR. SAT...VFR. SUN...MVFR TO IFR WITH SCATTERED RAIN SHOWERS. MON...NO SIG WX. && .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 NEAR TERM...LA CORTE SHORT TERM...LA CORTE LONG TERM...LAMBERT/GARTNER AVIATION...LA CORTE

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