Area Forecast Discussion
Issued by NWS State College, PA

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525 FXUS61 KCTP 092352 AFDCTP Area Forecast Discussion National Weather Service State College PA 652 PM EST Fri Dec 9 2016 .SYNOPSIS... A broad and very cold upper level trough over the Great Lakes and southeastern Canada will remain in place for the next few days. This weather feature and a well-aligned westerly low level flow off the lower Great Lakes will bring a prolonged period of lake effect snowfall and significant snow accumulations to northwest PA today through Saturday. High pressure will briefly build across the commonwealth late Saturday and Saturday night causing the Lake Effect snow bands to lift north of the region with a brief period of clearing elsewhere. Then, a weak low pressure system is likely to track east from the Ohio Valley and impact Pennsylvania with another bout of wintry weather Sunday into Monday. Unsettled weather will persist next week with additional storm chances during the mid...and late week periods. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Updated the forecasts with mainly minor changes. Primary short term issues include the snow and wind. Radar still shows a significant lake effect snow (LES) event. Some reports northeast of Warren had 11 inches and 9 inches in Chandlers Valley. These reports are several hours old and the snow continues. There is one elongated band that extends from Lake Erie down across Clinton County into Union and Snyder counties. Impressive length to the band. The band crosses I80 so it could produce periods of snow and blowing snow on I80 in southern Clinton County this afternoon and evening. The 3km HRRR shows the long band but it forecasts it to weaken over the next 2-8 hours. The HRRR shows snow and periods of moderate snow in Warren County through at least 8 AM Saturday. At least light snow in McKean county through the same period. All guidance focus the accumulating snow in our northwestern counties and limits snow; outside the one elongated band we currently have; to the northwestern 4 counties. Overnight lows in the teens and twenties but the wind will make it feel a good 10F colder at times. Most central areas and the southwest mountains will have flurries overnight with little or no accumulation to a dusting.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... The HRRR and 15Z SREF continue to support additional snow accumulation across the 2 NW PA counties into Saturday morning, some areas of light additional accumulation is possible across the west-central mtns and Laurel Highlands. Gradually improving conditions will take place later in the morning and afternoon as lake effect snow bands become more scattered and slowly wind down. Despite decreasing in intensity... WSW fetch off the lakes should continue to produce snow showers until Sat evening across the N Mtns. Skies should be clear across southern PA Saturday thanks to 1032 mb surface high building into the region. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... High pressure will bring a brief period of tranquility Sat evening. However, a developing overrunning scenario is expected Sunday into Monday, as weak low pressure lifts into the Eastern Grt Lks and high pressure remains lodged over northern New Eng. Enough cold air is in place to support a light snowfall across much of area by Monday AM, with GFS bringing light precip into the area on Sunday earlier than the ECMWF. Model consensus low track west of PA should bring in enough warm air to cause snow to change to rain (or a period of more problematic freezing rain) across Southern PA, and esp the Lower Susq Valley, a before precip tapers off later Monday. A bit cooler than normal temps indicated early next week, but longer range models indicate a significant cold front passage Wed with noticeably below normal temps filtering in for the rest of next week. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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Bands of lake effect snow showers will continue overnight into Saturday morning. Conditions will improve during the afternoon, as warming aloft occurs and winds shift more to the west and southwest. As of 6 PM, still an band of heavier snow showers from near BFD to just southwest of IPT. Expect a wide range of conditions overnight at BFD and JST. UNV and AOO should be VFR for much of the period. VFR conditions expected at IPT, MDT, and LNS. Earlier discussion below. Low pressure tracking from the lee of the Rockies to the Ohio Valley will bring a broad area of snow/rain to the area Sunday into early Monday. Outlook... Sun-Mon...Widespread MVFR/IFR in snow/rain. Becoming breezy Monday night with snow showers over the wrn 1/3. Tue...Mainly VFR. Wed...More snow showers possible.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... Lake Effect Snow Advisory until noon EST Saturday for PAZ005. Lake Effect Snow Warning until noon EST Saturday for PAZ004. && $$ SYNOPSIS...DeVoir NEAR TERM...Grumm SHORT TERM...Jung/DeVoir LONG TERM...Lambert/RXR AVIATION...Martin is the U.S. government's official web portal to all federal, state and local government web resources and services.