620 FXUS61 KCTP 302336 AFDCTP Area Forecast Discussion National Weather Service State College PA 636 PM EST Tue Dec 30 2025 .SYNOPSIS... * Gusty winds and lake effect snow showers will taper off this afternoon and evening. * A weak clipper system will bring light snow to Western and even parts of southern PA tonight. * A more significant system and second surge of arctic air will bring several inches of snow to locations west of US-219 on New Years Eve, along with a threat of snow squalls along the front. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... KEY MESSAGES: - Wind gusts taper off this afternoon as lake effect snow showers gradually weaken. - A clipper system will bring additional light snow accumulation, mainly west of US-219, overnight. - Light snow could affect the morning commute in the Lower Susquehanna Valley as well. -------------------------------------------------------------- Broad northwest flow continues to produce lake effect snow across western and central PA this afternoon. These arrow and slowly moving bands of LES will continue to bring mainly light accums of a coating to an inch of additional snow through this evening. Max temps today are a bit cooler than initial thought, ranging from the upper teens across the NW Mtns and ridge tops of the Laurel Highlands to the upper 20s across the larger metro areas in SE PA. Snow showers and areas of more persistent, heavier LES will retreat to the north and possibly out of our CWA temporarily as the mean flow within the well-mixed layer backs to about 240 deg later tonight through Wednesday. Hi-res guidance depicts a compact shortwave drifting southeast across western PA on this evening into Wednesday morning. This will bring additional, mainly light, snowfall accumulation to the laurel highlands and southern 1-2 layer of PA counties, thanks to enhanced and deeper Uvvel beneath the left exit region of a 100-100 kt upper level jet that will be moving along/over the Mason/Dixon Line. The Lake Effect Snow Warning remains in effect overnight to account for additional snow in Warren and McKean Counties, but amounts should not exceed 3 or 4 inches with tonight's system. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 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 /00Z WEDNESDAY THROUGH SUNDAY/... Lake effect snow streamers continue to move their way across the airspace this evening. Several sites are still experiencing snow showers and reductions in visibility. The western airfields of BFD, JST, and AOO will likely continue to experience MVFR to IFR visibility as these lake effect bands continue through. A more defined band of snow is currently approaching UNV, and a tempo group until 01Z has been included due to the band maintaining its strength. Elsewhere should remain VFR through tonight and into tomorrow. Winds will remain gusty into tomorrow morning. After tonight there will be a brief period of little to no snow activity, except for isolated upslope snow in the west. This dry period will last until late Wednesday afternoon when the next upper level short wave arrives. Confidence is increasing for a narrow snow squall band to arrive over the northwest and propagate down to the southeast Wednesday night. Additional adjustments will need to be made in future TAF packages for the timing of this band, but prob30s have been included to give a possible window of arrival for the snow squalls. 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 Wednesday to 4 PM EST Thursday for PAZ006-010-011. Winter Weather Advisory from 4 PM Wednesday to 10 AM EST Thursday for PAZ017-024. Winter Storm Warning from 4 PM Wednesday to 10 AM EST Thursday for PAZ033. && $$ SYNOPSIS...Lambert/Banghoff NEAR TERM...Lambert/Banghoff SHORT TERM...Banghoff LONG TERM...Banghoff AVIATION...Bowen