Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 090323 AFDCTP Area Forecast Discussion National Weather Service State College PA 1023 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 /UNTIL 8 AM SATURDAY MORNING/...
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Minor tweaks here and there - mainly to tighten up the onset time over the SE. Should be right around sunrise with the heaviest (term used liberally) snow rates in the middle of the day. Prev... High overcast, now, and temps may stay up a deg or two above guidance in the SE because of the clouds as they will be thickening and lowering. Could be a little light snow move into the SE cos right around sunrise. Otherwise, a fair night with temps into the teens north and just below 30F in the SE valleys.
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&& .SHORT TERM /8 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Have added an advy for 1-3" of snow in the far SErn counties. The sfc wave is not quite developing yet along the front per sat pics, but the short wave which will round the bottom of the trough tomorrow is still up in MN. Timing does look like the snow may linger another 3-6 hours in the SE. Therefore, QPF is a little higher than past runs as the development of the wave pushes more moisture into the area over a slightly longer time period. There is plenty of moisture available. 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. Steadiest snowfall pushes east of the area after sunset Saturday while upper trof crosses the GLAKS and Ohio Valley bringing sct of SW- to the northwest late in the day and at night. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... 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 /03Z SATURDAY THROUGH WEDNESDAY/... VFR cigs will continue overnight into tomorrow morning. The two systems moving into tomorrow will create two potential areas of restrictions. One in the southeast and the other in the northwest. So far the timing is slower so have adjusted TAF timing accordingly. Cig restrictions become likely over the SE for LNS and then for MDT after 18Z Saturday and improving by 09Z Sunday. As that system is exiting BFD and JST restrictions should begin between 09Z Sunday into 12Z 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... Winter Weather Advisory from 6 AM to 8 PM EST Saturday for PAZ065-066. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...Fitzgerald/Gartner AVIATION...DeVoir/Ceru

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