Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 300826 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 426 AM EDT THU OCT 30 2014 .SYNOPSIS...
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HIGH PRESSURE OVER THE OHIO VALLEY THIS MORNING WILL MOVE INTO THE APPALACHIANS TONIGHT. A VIGOROUS UPPER LEVEL TROUGH DIGGING THROUGH THE CAROLINAS WILL SUPPORT THE DEVELOPMENT OF A STRONG COASTAL STORM TRACKING JUST EAST OF THE NEW ENGLAND BENCHMARK THIS WEEKEND. THIS WILL LEAD TO A BRISK NORTH NORTHWEST WIND WITH MUCH COLDER AIR SUPPORTING SNOW SHOWERS OVER THE WESTERN ALLEGHENIES SATURDAY NIGHT. HIGH PRESSURE WILL RETURN TO THE AREA BEHIND THE DEPARTING STORM SYSTEM ON MONDAY WITH MODERATING TEMPERATURES INTO THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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PATCHY DENSE FOG OVR PORTIONS OF THE LOWER SUSQ VALLEY SHOULD LIFT OVER THE NEXT 1-2 HOURS AS A LIGHT NW WIND ADVECTS DRIER AIR INTO THE AREA. COOL AIR SPREADING DOWNWIND OF THE LOWER GREAT LAKES ALONG WITH WEAK UPSLOPE FLOW IS SUPPORTING AN EXPANSIVE AREA OF STRATOCU CLOUDS ACROSS THE NW ALLEGHENIES. THESE CLOUDS WILL PREVAIL THROUGH THE MORNING AS THE LLVL MSTR GETS TRAPPED UNDER THE SUBSIDENCE INVERSION ASSOCIATED WITH SFC HIGH MIGRATING SLOWLY EWD FROM THE OH VLY. MDL DATA SUGGESTS BINOVC THIS AFTN WHICH MAY BE A LITTLE TOO OPTIMISTIC. DOWNSLOPE FLOW SHOULD LEAD TO MORE SUN EAST OF THE ALLEGHENY FRONT. SHORTWAVE RIDGING ALOFT AND HIGH PRES AT THE SFC WILL COMBINE TO BRING DRY WX TO CENTRAL PA FROM THIS AFTN INTO TONIGHT. HIGH TEMPS WILL RANGE FROM THE MID 40S IN THE NW TO NEAR 60F IN THE LWR SUSQ. AMPLIFYING UPPER TROUGH PIVOT INTO THE UPPER GREAT LAKES BY 12Z FRI WITH A SFC LOW DEVELOPING NEAR LAKE HURON. MDL CONSENSUS SUPPORTS A SCHC OF SHOWERS OVER FAR NW PA BY THE END OF THE PD.
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&& .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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THE BIG STORY THROUGH THE LONG TERM PERIOD REMAINS THE TRACK OF THE LARGE UPPER LEVEL LOW THAT WILL PROGRESS THROUGH THE GREAT LAKES REGION ON FRIDAY...AND ITS PROGRESSION EASTWARD THIS WEEKEND.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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ALL MEDIUM RANGE GUIDANCE STILL SHOWS A POTENT SHORTWAVE DIVING SE FROM CANADA AND CARVING OUT A DEEP TROUGH OVR THE NORTHEAST CONUS BY SATURDAY. THE GFS ENSEMBLES VARY ON THE STRENGTH AND POSITION OF THIS LOW...THROUGH ALL SHARE SIMILAR TIMING. THE OPERATIONAL GFS AND EC ARE IN LINE WITH ONE ANOTHER AND HAVE THE UPPER LOW DIG SOUTH OF THE REGION AND ACTUALLY MOVES THROUGH THE CAROLINAS BEFORE MOVING OFF COAST. THE EC HAS TRENDED TOWARDS THE GFS...AND BOTH HAVE THE LOW FURTHER EASTWARD INTO THE ATLANTIC BEFORE IT TRAVERSES NORTHWARD. THE ASSOCIATED SFC CLIPPER LOW IS PROGGED TO TRACK ACROSS EASTERN OHIO/WESTERN PA LATE FRIDAY AND FRIDAY NIGHT...BRINGING THE BEST CHANCE OF PRECIP TO THAT AREA. BOTH GEFS AND OPER ECMWF/CANADIAN MDLS ALL POINT TOWARD A MAINLY RAIN EVENT FRIDAY. HOWEVER...AS UPPER LOW CUTS OFF SOUTH OF PA EARLY SATURDAY...THERMAL PROFILES...COUPLED WITH MOIST EASTWARD UPSLOPE FLOW MAY BECOME COLD ENOUGH TO PRODUCE A LIGHT COATING OF SNOW ACROSS THE HIGH TERRAIN OF THE ALLEGHENIES. EXPECT A RAIN...SNOW MIX POSSIBLE THROUGH THIS TIMEFRAME...AND ANY SNOWFALL WILL BE WET. AS THE DEVELOPING COASTAL LOW MOVES UP THE COAST LATE SATURDAY...A TIGHTENING PRESSURE GRADIENT AND NW FLOW WILL DRAW MUCH COLDER/DRIER AIR INTO THE REGION. OPERATIONAL RUNS AND NEARLY ALL ENSEMBLE MEMBERS KEEP COASTAL LOW FAR ENOUGH OUT TO SEA TO NOT DIRECTLY IMPACT CENTRAL PA. HOWEVER...COLD NW FLOW MAY PRODUCE LAKE EFFECT SNOW SHOWERS ACROSS THE NW MTNS SATURDAY NIGHT...EARLY SUNDAY MORNING. ESPECIALLY GIVEN THE STRONG...MOIST 850MB FLOW. TEMPS THIS WEEKEND WILL ALMOST CERTAINLY BE THE COLDEST YET THIS SEASON. ENSEMBLE MEAN 8H TEMPS POINT TOWARD DAYTIME HIGHS FROM THE UPPER 30S OVR THE ALLEGHENIES TO THE 40S ELSEWHERE. THE COLDEST NIGHT OF THIS OUTBREAK WILL LIKELY BE SUNDAY NIGHT...WHEN SFC HIGH BUILDS OVR THE REGION. THOSE LOCATIONS THAT HAVE YET TO SEE A FREEZE WILL LIKELY GET IT BY MONDAY AM. HIGH CONFIDENCE IN A PERIOD OF DRY WEATHER SUNDAY/MONDAY...WHEN ALL GUIDANCE BUILDS SFC HIGH AND ASSOC DRY AIR MASS ACROSS PA. AN APPROACHING COLD FRONT WILL BRING THE NEXT CHC OF SHRA BY MIDWEEK.
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&& .AVIATION /07Z THURSDAY THROUGH MONDAY/... THE MAIN AVN CONCERN NEAR TERM IS VLIFR FOG AT LNS/MDT WITH CONDS BELOW AIRFIELD MINS. WILL SHOW 2-3HR PERIOD OF THESE CONDS IN 06Z TAFS BEFORE SIGNALING SOME IMPROVEMENT BY 09Z AS A LGT NW WIND ADVECTS DRIER AIR INTO THE AREA. ELSEWHERE MVFR CIGS WILL PREVAIL AT BFD DUE TO COOL NW FLOW DOWNWIND OF LAKE ERIE. REMAINING SITES SHOULD STAY MAINLY VFR WITH SCT-BKN HI-BASED SC DECK ALTHOUGH JST COULD DROP TO MVFR LATER THIS MORNING. WEAK UPSLOPE FLOW UNDER SFC HIGH BUILDING EWD SUGGESTS LOW CIGS WILL CONTINUE DURING THE DAY AT BFD/JST WITH VFR CONDS EXPECTED EAST OF THE ALLEGHENY FRONT. OUTLOOK... FRI...VFR/MVFR EARLY WITH RAIN SHOWERS DEVELOPING WRN SXNS BY EVE. REDUCED CONDS LKLY FRI NIGHT WEST-CENTRAL 1/2 OF AIRSPACE WITH RAIN SHOWERS MIXING WITH/CHANGING TO SNOW SHOWERS WESTERN 1/3. SAT...MVFR/IFR WITH SCATTERED RAIN/SNOW SHOWERS WEST. VARYING CONDS FROM VFR-MVFR CENTRAL/EAST WITH OCNL -SHRA. N-NW WIND GUSTS 25-40 MPH. SUN...RAIN/SNOW SHOWERS ENDING WEST. LOW CIGS WEST BECOMING VFR. GUSTY NNW WINDS GRADUALLY DECREASING AREA-WIDE. MON...VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...FITZGERALD/STEINBUGL SHORT TERM...DEVOIR/FITZGERALD LONG TERM...FITZGERALD/CERU AVIATION...STEINBUGL

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