675 FXUS61 KCTP 310645 AFDCTP Area Forecast Discussion National Weather Service State College PA 145 AM EST Wed Dec 31 2025 .SYNOPSIS... * A weak clipper system will bring light snow to western and even parts of southern PA tonight. * A more significant system with surge of arctic air will bring several inches of snow to locations west of I-99 on New Years Eve, along with a threat of snow squalls along the front. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... Flow backing a little and is disrupting the LES bands. The bands should lift to the N and continue to weaken. The shortwave driving a clipper system in from the west is back over MI/IN, entering NWrn OH. The snow in that area is currently much lighter than we've had here at the office this evening. Most visibilities are 1-3SM there. As this system gets a little more into OH and then PA, it will likely lose some of it's meager moisture. With the speed of travel, only minor accums are expected downwind of the Allegheny Front. But, the staying power of the flow favorable for LES over the NW mtns should help them pick up a plowable snow overnight. Expect 1-3" for Warren Co and 1-2 for McKean Co. Upslope and best lift in general from the left-exit region of a jetlet diving to our S will help Somerset ridges get >1". Most places will see less, mainly a dusting to an inch, with only flurries past UNV-AOO-IPT. The wind will continue to lighten a little more through the night, but 5-12 sustained should continue to generate wind chills of 0-10F NW half and 10-17F SE half all night as both the temps and wind inch downward. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 PM THURSDAY/... In the wake of the shortwave, winds shift around to a more westerly fetch on Wednesday, which should direct lake effect snow bands north of US-6. We extended the Lake Effect Snow Warning through Thursday evening in anticipation of another more significant snowfall Wednesday evening through Thursday, but there will be a noticeable lull of 6 to 10 hours during the day on Wednesday with limited snow. By the mid to late afternoon (New Years Eve), a wave of low pressure will drift eastward across the Great Lakes, and drag an Arctic front south through the Commonwealth. Underneath a favorable left exit region of an upper jet, this front could produce a threat of snow squalls late Wednesday evening into the New Year. Current expectation is that the front and associated snow squall threat will move into northwest PA in the 6-8PM timeframe and then race southeast, crossing the I-99 corridor between 10PM and midnight and then getting into the Lower Susquehanna Valley between midnight and 2AM. Anyone planning to travel for the New Year should be prepared for the risk of snow squalls. If a Snow Squall Warning is issued, delay travel or exit the highway at the next opportunity. A snow squall produces blizzard-like conditions with gusty winds, heavy snow, and significantly reduced visibility. In addition to the threat of snow squalls, fairly robust moisture associated with this system will bring a more potent batch of snow to the region. Snowfall totals over 4" are possible west of US-219 with localized amounts >6" in the higher elevations of western Somerset County as well as in the typical lake effect zones of northwest PA. The Winter Storm Watch for Somerset County has been upgraded to a Winter Storm Warning from 4PM Wednesday through 10AM Thursday for the significant snowfall potential on the western ridges. A Winter Weather Advisory is in effect for the rest of the western Alleghenies (from Cambria up through Potter), where 3-5" of snow are likely, especially west of US-219. Lake effect streamer bands could linger into Thursday evening across the northwest, so the Lake Effect Warning and Winter Weather Advisories last a little longer there. Behind the cold front, a reinforcing shot of cold air will bring temperatures back into the single digits across the northern tier. Wind chills will drop into the minus single digits in the northern and western mountains on Thursday morning. Ensemble guidance favors wind chills staying above -10F, so a Cold Weather Advisory should not be needed at this time. Thursday afternoon will be the coldest of the week, with highs only in the mid teens west of I-99 and north of I-80, while getting into the upper 20s in the southeast. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... For Friday into the weekend, a prevailing trough pattern will reside over much of the eastern CONUS this period, underneath a deep upper low in eastern Canada. We'll see heights rise into the weekend, which will support moderating temperatures and lower chances for snow. Lows will range from the teens to twenties with highs in the twenties and thirties. A few locations across southern PA could crest the 40F mark on Monday and Tuesday. Ensemble guidance has the idea that a wave of low pressure will lift through the Great Lakes early next week. The last several model runs have continued to trend slower with this storm, but initial indications are for a quick-moving system that could bring some wintry mix to much of Pennsylvania. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Lake effect snow bands continue across mainly NW PA (BFD) this morning with some potential in these bands at JST/AOO/UNV through 12Z Wednesday. Low (~30%) chance of long-duration restrictions at AOO/UNV outside of snow bands so have trended towards recent GLAMP guidance given current radar trends that also are in fair agreement with HREF model guidance. BFD is likely to experience longer durations of IFR conditions throughout much of the 06Z TAF package as winds become more favorable for a longer duration of lake effect snow showers, especially after ~21Z Wednesday. Most likely window of any MVFR conditions at BFD will prevail in the 12-18Z Wednesday timeframe with low (~30%) confidence at this juncture. Further southeast at MDT/LNS, high (~80-90%) confidence in VFR conditions prevailing through the 06Z TAF package. The main thing of note in the 06Z TAF package remains the potential for snow squalls across the northwestern half of the forecast area after 00Z Thursday. Cold frontal passage will bring increased probabilities for locally heavy snowfall, with visibility likely to drop below 1/4SM in the heaviest snow squalls. Direct impact at the airfields remain uncertain at this time and there remains some uncertainty with respect to timing; however, have decided to include mentions in the 06Z TAF package due to high impacts at airfields if these conditions are to develop. Presence of low-level wind shear will increase just ahead of and along the cold frontal passage; however, lower (~20%) confidence on this aspect keeps mentions out of the 06Z TAF package, but will be something to monitor over the next couple of forecast cycles. Outlook... Thu...Chance of snow showers. Fri...Mainly dry. Slight chance of a snow shower at BFD and perhaps JST. Sat...Still a chance of a snow shower early at BFD, then VFR. Sun...Mainly VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... Lake Effect Snow Warning until 7 PM EST Thursday for PAZ004- 005. Winter Weather Advisory from 4 PM this afternoon to 4 PM EST Thursday for PAZ006-010-011. Winter Weather Advisory from 4 PM this afternoon to 10 AM EST Thursday for PAZ017-024. Winter Storm Warning from 4 PM this afternoon to 10 AM EST Thursday for PAZ033. && $$ SYNOPSIS...Dangelo/Banghoff NEAR TERM...Dangelo/Banghoff SHORT TERM...Dangelo/Banghoff LONG TERM...Banghoff AVIATION...NPB