Area Forecast Discussion
Issued by NWS State College, PA

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379 FXUS61 KCTP 112025 AFDCTP Area Forecast Discussion National Weather Service State College PA 325 PM EST Mon Dec 11 2017 .SYNOPSIS...
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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. A low presure system lifting northeast from the Great Plains will bring a southwest flow of milder air for the weekend.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Dry and milder conditions prevailing this afternoon thanks to high pressure building into the region. Downsloping subsidence resulting in clear skies across the south central mountains and now working through the southeast while stratocu lingers beneath subsidence inversion over the northwest mountains. Increasing mid and high level cloudiness arriving ahead of clipper over the Great Lakes on schedule, and will continue to thicken late this afternoon and evening as clouds increase farther east and south as well. Model consensus brings a batch of warm advection snowfall to western and northern sections this evening through overnight with a coating to 1 to 3 inches from I80 northward to the NY border respectively. Main impacts from this system will come as the cold front ushers in the coldest air of the season into PA later Tuesday, after FROPA Tue morning. As per collaboration with PBZ and BUF, Winter Storm Watch was already upgraded to Lake Effect Snow Warning for Warren County. Also expanded Winter Weather Advisory southward to include the rest of the Laurels (Clearfield, Cambria and Somerset Counties). && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... The coldest air of the season is forecast to arrive behind trailing arctic cold front Tuesday with more lake effect snow lasting through midweek. Northwest Warren County should get into some of the more robust lake effect banding later Tuesday and continuing into Wednesday. Lake Effect Snow Warning in effect for this, per collab with BGM, for widespread 10 to 15 inches, with local amounts up to 18 inches over extreme northwest Warren County. Model blended qpf supports a long duration advisory over Elk/Mckean counties, as well as Clearfield/Cambria/Somerset Counties where 4 to 8 inches are expected from 12z Tuesday through 18z Wednesday. 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 are actually separated from the best frontal/isallobaric forcing. Still isolated snow bursts and a few squalls are possible on Tuesday. It appears the Lower Susq River Valley will be spared from any snow squall threat Tuesday since 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 MONDAY/...
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Gusty northwest winds and snow showers will be the main issue Tuesday Night into Wed. Warnings and advisories in effect until 18Z Wed. Models show another system for Thursday. This system looks weak and EC a little further south, as been the case. Thus just have very light amts in. Maybe more of an impact for the far southeast, than system for Tue into Wed. After this the pattern supports a deep low tracking northeast from the Great Plains for the weekend, which will result in milder conditions. As been the case, the Gulf of Mexico is not really open, so looking at a mainly dry weekend. Complex pattern for Monday, perhaps a little light snow, but nothing major. Minor changes to the extended package.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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Mainly VFR conditions prevailing this afternoon, 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. Sat...Mainly VFR. Perhaps a snow shower north early.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 AM Tuesday to 1 PM EST Wednesday for PAZ005-010-017-024-033. Lake Effect Snow Warning from 7 AM Tuesday to 1 PM EST Wednesday for PAZ004. && $$ SYNOPSIS...DeVoir/Fitzgerald/Martin NEAR TERM...DeVoir/Fitzgerald SHORT TERM...DeVoir/Fitzgerald LONG TERM...Martin AVIATION...DeVoir/Martin/RXR

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