Area Forecast Discussion
Issued by NWS State College, PA

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133 FXUS61 KCTP 081256 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 756 AM EST MON FEB 8 2016 .SYNOPSIS... A SLOW MOVING AND DEEPENING UPPER TROUGH WILL SLIDE SOUTHEAST FROM THE UPPER GREAT LAKES...TO PENNSYLVANIA EARLY WEDNESDAY. A LONG- DURATION PERIOD OF SNOW WILL LIKELY RESULT IN A WIDESPREAD LIGHT TO MODERATE ACCUMULATION FOR MUCH OF CENTRAL PA LATE MONDAY INTO EARLY WEDNESDAY. LAKE EFFECT AND UPSLOPE SNOW SHOWERS WILL FOLLOW FROM MID WEEK INTO THE FIRST PART OF THE WEEKEND...WITH ADDITIONAL ACCUMULATION LIKELY IN THE FAVORED NORTHWEST SNOWBELT AND HIGHER TERRAIN ALONG THE ALLEGHENIES AND LAURELS. A MUCH COLDER WEATHER PATTERN IS EXPECTED BY LATER IN THE WEEK WITH A BLAST OF ARCTIC AIR FOR VALENTINES WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE SQUEEZE PLAY IS ON TODAY ACROSS THE REGION...AS A DEEP LOW OFF THE COAST MOVES NE...WHILE A SLOW-MOVING AND AMPLIFYING UPPER TROUGH TAKES ON A NEGATIVE TILT ACROSS THE MID ATLANTIC REGION LATE TONIGHT. MADE MINOR ADJUSTMENTS TO THE GRIDS TODAY. TIMING WAS QUITE GOOD. EXPECT SOME LIGHT SNOW INTO THE WESTERN AREAS BY EARLY TO MID AFT...AND EASTERN AREAS AFTER DARK. LOOKS LIKE HIGHEST AMTS LATE TODAY AND EARLY TONIGHT WOULD BE ACROSS SOMERSET AND CAMBRIA COUNTIES. POSTED AN WINTER WEATHER ADVISORY FOR THIS AREA. WHILE THE SNOW COULD START AS RAIN...WET BULB ZERO ELEVATION CLOSE TO THE SFC PAINTS A SNOW...RATHER THAN RAIN/SNOW MIX IN MOST PLACES LATER MONDAY AFTERNOON/EVENING...EXCEPT FOR PERHAPS THE SUSQ VALLEY AT OR BELOW 900 FT MSL. && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/... IT IS FAIRLY CERTAIN CENTRAL PA WILL EXPERIENCE A PROLONGED PERIOD OF LIGHT...POSSIBLY MODERATE SNOW /IN ONE OR TWO SLOW MOVING AND RATHER NARROW FGEN BANDS/ DURING THE MONDAY NIGHT INTO TUESDAY PERIOD. AFTER DISCUSSION WITH PHI AND LWX...ALONG WITH NEW WPC GRAPHICS...HAVE ISSUED WINTER STORM WATCH AFTER 05Z TUE FOR OUR 3 SE COUNTIES. A WELL-DEFINED UPPER TROUGH/CIRCULATION TO THE WEST...WILL GRADUALLY PHASE-IN ADDITIONAL SHORTWAVE ENERGY AS IT DIGS SOUTHEAST THROUGH THE GREAT LAKES...EVOLVING INTO A CLOSED LOW WITHIN A BROAD/ANOMALOUS MEAN TROUGH MIGRATING SLOWLY FROM THE OHIO VALLEY INTO THE NORTHEAST STATES THROUGH MIDWEEK. THE COMPLEX EVOLUTION/AMPLIFICATION OF THE LARGE SCALE TROUGH CHARACTERIZED BY SEVERAL EMBEDDED SHORTWAVE DISTURBANCES CONTINUES TO RESULT IN A COMPLICATED/LOWER CONFIDENCE SNOWFALL FORECAST. THUS HAVE WATCH IN JUST THE HIGHEST AREA OF EXPECTED SNOWFALL. AGAIN...NOT A LOT TO WORK WITH...BUT USED THE LOCATION OF INVERTED TROUGH AND TREND OF MODELS ALONG WITH WPC GRAPHICS AND OTHERS TO KEY ON SMALL AREA OF HIGHEST CONCERN. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... WHAT WE DO KNOW IS THAT A PROLONGED PERIOD OF SNOW IS LIKELY FROM MONDAY NIGHT THROUGH TUESDAY...FOLLOWED BY A TRANSITION TOWARD A LAKE EFFECT/UPSLOPE SNOW PATTERN LATER ON WED. ANOMALOUS WESTERN US RIDGE/EASTERN US TROUGH PATTERN WILL BE IN PLACE THROUGH MID WEEK. THE GLOBAL ENSEMBLE MEANS GENERALLY KEEP THIS PATTERN CONFIGURATION INTACT INTO THE WEEKEND BUT AT A SLIGHTLY DECREASING AMPLITUDE..ESPECIALLY THE WESTERN US RIDGE. AS THE BROAD UPPER LEVEL CIRCULATION DEPARTS OVER THE NORTHEAST TOWARD THE END OF THE WEEK...THE GLOBAL MODELS SHOW IT BEING REPLACED BY A POLAR VORTEX DROPPING SOUTH FROM THE ARCTIC. COLD AIR WILL BEGIN SPILLING SOUTHWARD FROM CANADA LATER IN THE WEEK REINFORCED INITIALLY BY A SECONDARY FRONT ON THURSDAY...FOLLOWED BY A SIGNIFICANT ARCTIC AIR INTRUSION FOR VALENTINE`S WEEKEND. RESIDUAL SNOWS ASSOCIATED WITH THE UPPER TROUGH ON WED SHOULD TRANSITION TOWARD LAKE EFFECT/UPSLOPE FOR SEVERAL DAYS THU-SAT WITH ADDITIONAL ACCUMULATION LKLY OVER THE FAVORED AREAS DOWNWIND OF LAKE ERIE AND IN THE HIGHER TERRAIN OF THE ALLEGHENIES/LAURELS. CONFIDENCE IS HIGH IN THE FCST COLD PATTERN WHICH SHOULD PEAK OVER THE WEEKEND. MAX/MIN TEMPERATURE DEPARTURES OF 20 DEGREES BELOW CLIMO ARE PROBABLE SAT-SUN. WIDESPREAD SUB ZERO WIND CHILLS APPEAR LIKELY SATURDAY NIGHT INTO EARLY SUNDAY...WITH PROJECTED MINIMUM WC VALUES BETWEEN -10 TO -25 DEGREES BELOW ZERO. && .AVIATION /13Z MONDAY THROUGH FRIDAY/... A FADING NARROW RIDGE OF HIGH PRESSURE BETWEEN TWO WEATHER SYSTEMS IS BRINGING VFR CONDITIONS TO CENTRAL PA THIS MORNING. HIGH CLOUDS WILL THICKEN OVERHEAD TODAY AS AN UPPER LEVEL TROUGH AND WEAK COLD FRONT APPROACH. THE UPPER LEVEL TROF WILL DROP DOWN OVER THE AREA THIS AFTERNOON...SPREADING SNOW INTO WESTERN AREAS BY MID AFTERNOON THEN SPREADING EASTWARD THIS EVENING. THE COMPLEX WEATHER PATTERN WILL RESULT IN WIDESPREAD... BUT MAINLY LIGHT TO OCCASIONALLY MODERATE... SNOW TONIGHT INTO TUESDAY NIGHT. WHILE THERE MAY BE BREAKS FROM TIME TO TIME...EXPECT FAIRLY WIDESPREAD SNOW/SNOW SHOWERS AND ASSOCIATED RESTRICTIONS OVER MUCH OF THE REGION THROUGH THAT PERIOD. LOOKING AHEAD...SNOW SHOWERS BECOME CONFINED TO WESTERN HIGHER TERRAIN MID/LATE WEEK AS SHOT OF QUITE COLD AIR ARRIVES ON NW FLOW. OUTLOOK... TONIGHT INTO TUE NIGHT...PERIODS OF LIGHT SNOW. IFR CONDITIONS. WED...IFR/MVFR IN SHSN WRN AIRSPACE. MVFR-VFR CIGS CENTRAL/EAST. SFC WIND GUSTS 20+KT FROM 270-300. THU-FRI...MVFR IN -SHSN W MTNS. VFR ELSEWHERE. && .CTP WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO MIDNIGHT EST TONIGHT FOR PAZ024-033. WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE TUESDAY NIGHT FOR PAZ064>066. && $$ SYNOPSIS...GARTNER/MARTIN NEAR TERM...MARTIN SHORT TERM...MARTIN/STEINBUGL LONG TERM...MARTIN/STEINBUGL AVIATION...RXR

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