Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 081902 AFDCTP Area Forecast Discussion National Weather Service State College PA 202 PM EST Fri Dec 8 2017 .SYNOPSIS... Low pressure over the Gulf of Mexico will track northward off the east coast late tonight and Saturday. A deep upper level trough will remain over the eastern conus through next week with clippers potentially affecting Pennsylvania Monday night and Thursday. && .NEAR TERM /THROUGH TONIGHT/...
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High pressure maintaining fair and cold conditions across central PA this afternoon as moisture builds well south of the region. The surface ridge axis will keep things dry across all of central PA through late tonight before moisture backs WNW into my south central and southeast in the form of light snow by early Saturday morning. Expect some light snow to develop over southern York and Lancaster Counties after 08z.
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Blend of current guidance indicates that the western edge of the precip (snow) shield is still expected to reach the I-81 corridor during the daylight hours of Saturday. 12z QPF looks similar to previous runs with reasonable confidence in 1-2 inch snowfall over portions of the Lower Susq River Valley and South Central Mountains along and east of I-81. Steadiest snowfall pushes east of the area after 18z Saturday while upper trof crosses the GLAKS and Ohio Valley bringing a chc of SW- to the northwest late in the day and at night.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... A potent mid level shortwave will sweep across the region Saturday night, as coastal low tracks into the Canadian Maritimes. Snow showers with light accumulations are most likely over the higher terrain of the Alleghenies Saturday night, but may coat the ground quickly into parts of east- central PA. A period of lake effect and orographic snow showers should continue into Sunday with gusty winds and wind chills mostly in the teens. Lake effect trajectories back to the west-southwest into Monday as the next shortwave digs southeast through the MS/OH Valley. There is a decent model spread in the low track and evolution of this system, but regardless of the details this feature should provide a good opportunity for most of the area to see some snow early next week. The coldest air of the season is forecast to arrive behind this system with a shot of arctic air and more lake effect snow lasting through midweek. Both ECENS and GEFS indicate another clipper is likely to affect the area next Thursday with another light snow potential. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... Mainly VFR conds across the region today, as WAA aloft in advance of shortwave brings cirrus clouds to mainly the SE half of CWA through the TAF period. Wind will remain from the west at speeds of 5-10 mph before becoming light later in the day. Cig restrictions become likely over the SE half of CWA on Sat as a low pressure area slides north off the Atlantic Coast. Chances are increasing for a period of light snow from midday Sat into Sat eve over SE half that could produce IFR restrictions. Focus then shifts to the western/northern mountains Sat night and Sunday as a strong trough brings brisk NW flow, cig restrictions, and the potential for light snow with some heavier squalls. Outlook... Sat...Thickening clouds with afternoon and nighttime snow showers/vis reductions SE half. Sat Night-Sun...AM snow showers/vis reductions likely Allegheny Plateau. Scattered squalls also poss. Mon...PM light snow possible, mainly northwest Pa. Mon night and Tuesday...Periods of light snow. Widespread MVFR likely, with periods of IFR and brief LIFR cigs and vsbys. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...DeVoir/Fitzgerald NEAR TERM...DeVoir/Fitzgerald SHORT TERM...DeVoir/Fitzgerald LONG TERM...Fitzgerald/Steinbugl AVIATION...DeVoir/RXR is the U.S. government's official web portal to all federal, state and local government web resources and services.