Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 111211 AFDCTP Area Forecast Discussion National Weather Service State College PA 711 AM EST Mon Dec 11 2017 .SYNOPSIS... An alberta clipper will track just north of Pennsylvania tonight, with a trailing arctic cold front sweeping through the area Tuesday. A deep upper level trough will remain over the eastern conus through the rest of this week with another weak clipper likely affecting the area Thursday. The upper trough will likely lift out by next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A moisture-starved shortwave is moving through central Pa early this morning, accompanied by a few snow showers/flurries over the northern mountains. The shortwave will be passing east of the area by 12Z. However, will maintain mention of a few lingering snow showers across the northwest mountains until late morning in association with a dying cold front sagging south from the Grt Lks. For most of central Pa, expect a dry and slightly milder Monday, as ridging briefly works into the region. Downsloping subsidence should result in mostly sunny skies east of the mountains, while stratocu lingers beneath subsidence inversion over the northwest mountains. By late in the day, expect increasing mid and high level cloudiness to arrive ahead of clipper over the Grt Lks. Model soundings are well mixed to at least 900mb, where temps of -4C to -6C should translate to max temps from around 30F over the northwest mountains, to near 40F across the Lower Susq Valley. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... All model guidance tracks clipper north of Pa tonight, which should keep the most substantial snow north of Pa. However, blend of latest guidance still supports a period of light overrunning snow across northern Pa, with accums generally in the 1-3 inch range. An examination of model omega/temperature time sections indicates bulk of lift occurring tonight will be well beneath the DGZ, indicating snow/water ratios not much above 10 to 1. The coldest air of the season is forecast to arrive behind trailing arctic cold front Tuesday with more lake effect snow lasting through midweek. Between light clipper snow tonight and Tue-Wed lake effect, WPC graphics indicate about a 50 pct chance of exceeding winter storm criteria across the snowbelt of Warren County, so have issued a wint storm watch up there. Further east, all model guidance indicating limited potential of reaching warning criteria. However, model blended qpf supports a long duration advisory over Elk/Mckean counties. Still some concern about snow squalls accompanying cold front passage between 12Z-18Z Tuesday. However, lower tropospheric lapse rates look less impressive than would be expected for a significant snow squall event and 00Z model CAPES are nonexistent until front reaches the Lower Susq Valley, where boundary layer temps appear borderline for shra vs shsn and surface temps are likely to be near 40F. Gusty wnw winds will develop Tuesday behind the cold front with bufkit soundings supporting frequent gusts of 30kts+ by late in the day. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Model soundings suggest wind advisory criteria is possible early Wed, as large scale subsidence and pressure fall/rise couplet moves through. Have added blowing/drifting to the forecast, where sig snow is expected over the northwest mountains. Base of upper trough and coldest air will be over the region Wed, with temps likely not reaching 20F over the Allegheny Plateau and only reaching the upper 20s across the LSV. Lake effect snow is likely to abate late Wed, as weak surface ridge builds in from the Grt Lks. Med range guidance indicates another clipper is likely to affect the area Thursday with another potential light snowfall. After that, ECENS and GEFS both indicate upper trough will lift out, resulting in a marked warm up next weekend. Latest EC ensemble MOS guidance indicating temps returning to near or slightly above climo by next weekend. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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Lake flow will keep snow showers over the KBFD terminal off and on through the mid morning hours. Restrictions there will remain IFR through about 15z, then improve to MVFR. MVFR cigs will persist at KJST into the early afternoon, and brief MVFR cigs will be poss mid morning in parts of the central mountains. Mainly VFR conditions are forecast elsewhere, with a scattered to broken deck between 5000 and 12000 feet. Winds will be westerly at 5 to 10 knots. An alberta clipper will track just north of Pennsylvania tonight, with a trailing arctic cold front sweeping through the area Tuesday. Light snow will begin to impact NW mountains after midnight, and spread into the NW half around 10-14z Tues. The snow will be accompanied by cig/vsby reductions - again primarily over the NW half of CWA. Some concern about snow squalls accompanying cold front passage between 12Z-18Z Tuesday. Then gusty WNW winds develop with frequent gusts of 30kts+ by late in the day. Outlook... Late tonight and Tuesday...Periods of light snow - mainly NW half. Widespread MVFR likely, with periods of IFR and brief LIFR cigs and vsbys NW. Wed...Snow showers with IFR NW Mtns. Sct snow showers with MVFR NW half. Otherwise VFR. Thu-Fri...Sct snow showers. Reductions west.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 PM this evening to 4 PM EST Wednesday for PAZ005-010. Winter Storm Watch from this evening through Wednesday afternoon for PAZ004. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald AVIATION...RXR

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