Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 072043 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 343 PM EST SUN FEB 7 2016 .SYNOPSIS... A SLOW MOVING AND DEEPENING UPPER TROUGH WILL SLIDE SOUTHEAST FROM THE UPPER GREAT LAKES. A LONG-DURATION PERIOD OF SNOW WILL LIKELY RESULT IN A WIDESPREAD LIGHT TO MODERATE ACCUMULATION FOR MUCH OF CENTRAL PA MONDAY INTO WEDNESDAY. LAKE EFFECT AND UPSLOPE SNOW SHOWERS WILL CONTINUE THROUGH THE END OF THE WEEK 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 /THROUGH MONDAY/... SPLENDID MID WINTER AFTERNOON FOR OUTDOOR ACTIVITIES...COMPLETE WITH ABUNDANT SUNSHINE...GENERALLY LIGHT WIND...AND TEMPS BETWEEN 7 AND 10 DEG F ABOVE NORMAL /WITH THE GREATEST DEPARTURES OCCURRING ACROSS THE WRN MTNS...WHERE TEMPS WERE ABLE TO CLIMB INTO THE LOWER 40S/. ELSEWHERE...THE MERCURY IS TOPPING OUT IN THE MID TO UPPER 40S. VARYING COVERAGE OF MAINLY THIN CIRRUS WAS NOTED THIS MID AFTERNOON HOUR...WITH SOME ALTO CU DEVELOPING/DRIFTING NNE ACROSS FAR NWRN PENN. A STRENGTHENING SFC AND UPPER LOW /JUST E OF MYRTLE BEACH SC LATE THIS AFTN/ WILL MOVE NORTHEAST...OFF THE VA COAST LATE TONIGHT/MONDAY MORNING...BRUSHING THE MID ATLANTIC PIEDMONT AND COASTAL AREAS WITH SOME WINTRY PRECIP AND WIND. FOR THE OVERNIGHT HOURS...WE/LL SEE LITTLE CHANGE IN THE CLOUD COVER THROUGH 06Z...BEFORE A SLOW INCREASE IN CLOUDINESS OCCURS LATE. CONSENSUS ALL BLEND OF MODELS INDICATES THAT IT WILL STILL BE RELATIVELY MILD WITH LOWS IN THE MID TO UPPER 20S IN MOST AREAS...WITH A FEW SPOTS DIPPING INTO THE L20S. THE SQUEEZE PLAY IS ON FOR MONDAY ACROSS THE REGION...AS A POWERFUL 976 MB SFC LOW MOVES NE...WELL TO THE SOUTH OF LONG ISLAND AND CAPE COD...WHILE A SLOW-MOVING AND AMPLIFYING UPPER TROUGH TAKES ON A NEGATIVE TILT ACROSS THE MID ATLANTIC REGION LATE MONDAY/MONDAY NIGHT. DUAL...TO MULTI-LAYERED CLOUDS WILL GRADUALLY LOWER/THICKEN UP FROM THE WEST AND SOUTH DURING THE DAY...WITH OVC SKIES BY LATE AFTERNOON IN ALL AREAS BUT PERHAPS THE SUSQ VALLEY AND POINTS JUST TO THE EAST. 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. LATEST SREF AND NAM ARE IN DECENT AGREEMENT WITH THE ONSET TIME OF THE SNOW - LATE IN THE AFTERNOON ACROSS THE LAURELS...WHILE THE GEFS MEAN IS 2-3 HOURS SLOWER. A COATING TO LESS THAN ONE INCH OF SNOW IS POSSIBLE ACROSS THE SW THIRD OF THE CWA BY MONDAY EVENING /BUT MAINLY AT ELEVATIONS 1500 FT MSL AND HIGHER SINCE HIGH TEMPS PRIOR TO THE PRECIP BEGINNING WILL BE IN THE U30S TO L40S. IT IS FAIRLY CERTAIN CENTRAL PA WILL EXPERIENCE A PROLONGED PERIOD OF LIGHT...POSSIBLY MODERATE PRECIP /IN ONE OR TWO SLOW MOVING AND RATHER NARROW FGEN SNOW BAND/ DURING THE MONDAY NIGHT THROUGH TUESDAY PERIOD OF THE FORECAST. CONFIDENCE REMAINS LOW TO MODERATE ON LOCATION OF THE SNOW...BUT MODERATE ON THE AMOUNTS WHICH SHOULD BE SEVERAL INCHES IN MANY LOCATIONS. THE LONG DURATION AND LIGHT TO MODERATE AMOUNTS EXPECTED DON/T FALL INTO OUR WATCH/WARNING CRITERIA AT THIS POINT IN TIME...AND ARE ONLY NEAR THE THRESHOLD OF OUR WINTER WEATHER ADVISORIES OF 3 INCHES/12 HOURS /2 INCHES/12 HOURS ACROSS THE LOWER SUSQ BEGINNING THIS PAST FALL/. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... A WELL-DEFINED UPPER TROUGH/CIRCULATION OVER THE ARROWHEAD OF MN THIS AFTERNOON 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. DESPITE DECENT AGREEMENT ON THE OVERALL PATTERN...THERE IS STILL A SOME SPREAD REGARDING IMPORTANT DETAILS SUCH AS THE QPF PLACEMENT AND LOCATION OF SNOW AMOUNTS. THERE MAY ALSO BE BOUNDARY LAYER TEMPERATURE ISSUES THAT INTRODUCE FURTHER COMPLEXITY TO AN ALREADY CHALLENGING SNOW FCST. IN THIS KIND OF FORECAST DILEMMA WITH VARYING MODEL SIMULATIONS AND SMALL SCALE DIFFERENCES...WE CONTINUED TO EMPLOY A RELATIVELY CONSERVATIVE STRATEGY FOR FCST SNOW AMOUNTS BY INCREMENTALLY NUDGING TOWARD A MULTI-MODEL CONSENSUS AND WPC WINTER WEATHER GUIDANCE. 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 INTO WEDNESDAY. THE STORM TOTAL SNOWFALL COMPILED OVER A 48-60 HOUR PERIOD SHOWS A BROAD AREA OF 3+ INCHES WITH HIGHER AMOUNTS SHADED TOWARD THE WESTERN AND SOUTHERN PORTIONS OF THE AREA. THE MAXIMUM FCST SNOW AMOUNTS AT THIS TIME ARE FOCUSED OVER THE HIGHER TERRAIN IN SOMERSET COUNTY. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... 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 /21Z SUNDAY THROUGH FRIDAY/... HIGH PRESSURE OVER THE AREA WILL RESULT IN AREAS OF MAINLY HIGH CLDS LATE TODAY AND TONIGHT...THOUGH THE SOUTHEAST TAF SITES. /KLNS AND KMDT/ WILL SEE A THICKER SHIELD OF CIRROSTRATUS FROM THE NW EDGE OF AN INTENSIFYING WRN ATLANTIC SFC LOW. SOME MID-LEVEL ALTO CU WILL SPREAD OVER THE WRN PENN TAF SITES LATER TONIGHT/MONDAY MORNING...BEFORE LOWERING TO BORDERLINE MVFR THERE MONDAY AFTERNOON. A COMPLEX WEATHER PATTERN MAY RESULT IN SOME SNOW AND COLDER TEMPERATURES AFTER TODAY AS A DEEP UPPER TROUGH BECOMES CARVER OUT OVER THE EASTERN U.S. OUTLOOK... MON...PM LGT SNOW POSSIBLE MID TO LATE AFTERNOON...MAINLY ACROSS THE W MTNS /KJST AND KBFD/. MON NIGHT AND TUE...LGT SNOW LIKELY...ESP CENTRAL AND WRN MTNS. WED...IFR/MVFR IN SHSN WRN AIRSPACE. MVFR-VFR CIGS CENTRAL/EAST. SFC WIND GUSTS 20+KT FROM 270-300. THU AND FRIDAY...MVFR IN -SHSN POSSIBLE W MTNS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...FITZGERALD/LAMBERT SHORT TERM...STEINBUGL LONG TERM...STEINBUGL AVIATION...LAMBERT

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