Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 251048 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 548 AM EST THU DEC 25 2014 .SYNOPSIS... INTENSE LOW PRESSURE WILL MOVE ACROSS SOUTHERN QUEBEC THIS MORNING AND PUSH ITS SOUTHWARD TRAILING COLD FRONT AND AREA OF LIGHT OT MODERATE RAIN ACROSS THE MID ATLANTIC COASTAL PLAIN THIS MORNING. ASIDE FROM SOME SCATTERED SNOW SHOWERS ACROSS THE WESTERN MOUNTAINS TODAY...DRIER BUT WINDY CONDITIONS WILL PREVAIL. A LARGE AREA OF HIGH PRESSURE WILL BUILD NORTHEAST FROM THE GULF COAST REGION BRINGING FAIR WEATHER WITH LIGHTER WIND FOR TONIGHT AND FRIDAY. A WEAK COLD FRONT WILL DRIFT ACROSS THE STATE SATURDAY...FOLLOWED BY A WEAK WAVE OF LOW PRESSURE RIDING NORTHEAST ALONG IT BRINGING A FEW PERIODS OF RAIN SATURDAY NIGHT AND SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SHARP COLD FRONT HAS PUSHED TO THE NEW JERSEY COAST EARLY TODAY. THE AREA OF LIGHT TO MDT SHOWERS ALONG /AND FOR ABOUT 150 KM IN THE WAKE OF THE FRONT/ WILL EXIT OUR FAR EASTERN ZONES BY 1130Z. AFTER A BRIEF LULL IN PEAK GUSTS THE PAST SEVERAL HOURS...BUFKIT SOUNDINGS AND MOMENTUM TRANSPORT INDICATE THE LIKELIHOOD OF QUICKLY STRENGTHENING GUSTS TO 40 TO 50 MILES LATER THIS MORNING...AS THE WELL-MIXED LAYER DEEPENS TO BETWEEN 4-6 KFT AGL. COLDER AIR ALOFT AND SLIGHTLY CYCLONIC FLOW AT THE SFC WILL LEAD TO SOME SNOW SHOWERS ACROSS THE WESTERN MTNS BETWEEN 12-19Z AS THE BASE OF THE SUBSIDENCE INVERSION RISES TO 4-6 KFT AGL. THE HEIGHT OF THIS INVERSION BASE CRASHES TO BETWEEN 2-3 KFT AGL BY 00Z FRIDAY...CUTTING OFF THE SNOW SHOWERS AND HELPING TO TRIM THE WINDS /AND PEAK GUSTS/ BY 10 KTS OR MORE. OUTSIDE TEMPERATURES /WHILE PRESENTS ARE BEING OPENED THIS MORNING/ WILL STAY STEADY OR FALL SLIGHTLY - VARYING FROM THE MID AND UPPER 30S ACROSS THE WESTERN MTNS...TO THE LOWER AND MID 40S THROUGHOUT THE SUSQ VALLEY. THE CENTRAL RIDGE-VALLEY REGION WILL EXPERIENCE LITTLE MORE THAN A PASSING LIGHT RAIN OR SNOW SHOWER TODAY. AGAIN...THE FALLING INVERSION HGTS WITH APPROACH OF SFC RIDGING FROM THE SOUTHWEST LATER TODAY SHOULD CAUSE ANY MTN SNOW SHOWERS TO TAPER OFF DURING THE AFTN AND RESULT IN SOME BREAKS IN THE CLOUD COVER...ESP ACROSS THE LOWER SUSQ VALLEY. WITH SFC TEMPS EXPECTED TO BE ABV FREEZING EVERYWHERE /AND ONLY IN THE MID TO UPPER 30S ACROSS THE WESTERN MTNS/...THE LIGHT SNOW SHOWERS ARE NOT EXPECTED TO ACCUMULATE...EXCEPT FOR PERHAPS A DUSTING OVR THE HIGHEST RIDGETOPS. ENS MEAN 925/850 TEMPS SUPPORT HIGH TEMPS TODAY RANGING FROM THE M30S OVR THE ALLEGHENY MTNS...TO THE U40S ACROSS THE LOWER SUSQ VALLEY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... SFC HIGH PRESSURE WILL BUILD NE INTO THE REGION LATE TONIGHT AND FRIDAY...ACCOMPANIED BY DECREASING WSW WIND AND CLEARING SKIES ACROSS ALL BUT PORTIONS OF THE WESTERN MTNS WHERE SOME SHALLOW STRATUS/STRATOCU WILL BE PRESENT...ALONG WITH THE CHC FOR SOME VERY LIGHT SNOW OR -FZDZ AS CLOUD TEMPS WILL BE JUST A FEW TO SEVERAL DEG C BELOW ZERO. LOW TEMPS TONIGHT WILL BE FAIRLY UNIFORM AND IN THE MID TO UPPER 20S. && .LONG TERM /FRIDAY 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 /12Z THURSDAY THROUGH MONDAY/... 03Z TAFS SENT. STRONG DRY PUNCH AND WIND FIELDS HAVE RESULTED IN 49 KNOT GUST AT DUJ. GUSTY WINDS WILL BE THE MAIN ISSUE OVERNIGHT. LOW CIGS STILL ACROSS MUCH OF THE AREA...WITH LLWS. WINDS WILL SLOWLY DIE DOWN DURING THE DAY ON THU. LOW CIGS WILL PERSIST THE FIRST PART OF CRHISTMAS ACROSS THE AREA. EXPECT CONDITIONS TO BECOME VFR LATER IN THE DAY. NOT LOOKING BAD INTO FRIDAY AND SAT. OUTLOOK... FRI...MAINLY VFR. SAT...VFR. SUN-MON...MVFR TO IFR WITH SCATTERED RAIN AND SNOW SHOWERS. && .CTP WATCHES/WARNINGS/ADVISORIES... WIND ADVISORY UNTIL NOON EST TODAY FOR PAZ004>006-010>012-017- 018-024-033. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/GARTNER AVIATION...MARTIN

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