FXUS61 KCTP 040426 AFDCTP Area Forecast Discussion National Weather Service State College PA 1126 PM EST Tue Dec 3 2024 .SYNOPSIS... * Cold and breezy conditions continue through the end of the week with temperatures below the historical average for early December * Widespread snow showers, localized snow squalls, and strong winds 40-50 mph will likely result in hazardous travel impacts late Wednesday night into Thursday * Lake effect and upslope snow continues into late week with significant storm total accumulations probable in the favored snowbelts and higher ridgetop elevations && .NEAR TERM /THROUGH WEDNESDAY/... A few light snow showers remain possible through late this evening in the vicinity of a stalled surface trough over North Central PA, where there remains a narrow ribbon of instability and low level convergence. Otherwise, boundary layer flow backing to the southwest will push lake effect snow showers north of the border tonight. Low level moisture trapped beneath a subsidence inversion, combined with an upsloping WSW flow, should yield persistent stratus over the Allegheny Plateau tonight. Elsewhere, mostly clear skies and a diminishing breeze should allow temps to fall a bit below NBM guidance tonight. However, model soundings indicate thickening mid and high level cloudiness will overspread the entire region late tonight, putting the breaks on radiational cooling. WAA ramps up Wednesday ahead of a deepening upstream trough, with thickening mid and high level clouds indicated by model RH profiles. There could even be a bit of very light snow or flurries, mainly over the N Mtns where a southerly flow is forced to ascend the higher terrain north of I-80. See no reason to deviate from NBM max temps, which range from around 30F over the N Mtns, to around 40F across the Lower Susq Valley. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... A deepening upper level trough tracking through the Great Lakes will push an arctic cold front through the area Wednesday night and early Thursday morning. Steep lower tropospheric lapse rates and sufficient low level moisture support the possibility of an intense burst of snow squalls accompanying the front, leading to potentially hazardous travel conditions, particularly over the Laurel Highlands and Allegheny Plateau with near-blizzard conditions possible, as strong wind gusts arrive with the front. Any snow associated with the front should be in the half inch to 2 inch range. However, lake effect snow showers will then develop behind the cold front Thursday into Thursday evening, with a WNW boundary layer flow targeting the NW Mtns for potentially heavy additional snow. A winter storm watch remains up along the spine of the Alleghenies. However, highest confidence in warning upgrades are across the lake effect snowbelt regions of Warren/Mckean counties. Forecast time/height progs support high snow/water ratios over the NW Mtns Thursday PM with most lift occurring within the DGZ. Forecast soundings and strong pressure rises/BL mixing behind the sharp arctic cold front will support peak wind gusts 45-50 mph over the majority of the area Thursday. We issued a wind advisory for the entire CWA from 1AM-7PM Thursday. However, latest model guidance indicates the onset of the strongest winds may be a bit later than 1AM. Inversion heights fall a bit Thursday night into Friday, causing lake effect snow showers to diminish somewhat. However, a cold WNW flow should continue to produce persistent light lake effect snow across primarily the NW Mtns. Friday will be another cold day, as some of the greatest 850mb temp anomalies pass over the state. Expect highs at or below the freezing mark across most of central PA. Daytime max temperature departures from the historical average will be 10 to 20 degrees! Wind chills Friday morning will be in the single digits to mid teens. Lake effect snow should be in the late innings heading into Friday night as mean trajectories start to back to the west- southwest. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... A WNW flow in the cloud bearing layer will likely maintain lingering lake effect snow over the Northwest Mtns into Sat AM. However, inversion heights look relatively low, so any additional accumulation should be light. Fair and chilly conditions appear likely Sat PM, as surface ridging builds across the state. Upper level ridging and a surface high passing off of the East Coast should translate to fair and significantly milder weather Sunday, as the return southwest flow develops. GEFS 2m temp anomalies suggest highs will be several degrees above average, ranging from around 40F over the N Mtns, to near 50F in the southern valleys. The bulk of medium range guidance supports a period of rain Monday associated with warm advection ahead of a weakening shortwave lifting into the Eastern Grt Lks. Can't completely rule out an initial wintry mix over the higher terrain Monday AM, but lack of a blocking high and current progged thermal fields point toward rain. The low level jet and plume of highest pwats should shift east of the region by Monday night, causing rain to taper off. Ensemble plumes currently indicate most likely rain totals by late Monday of 0.25 to 0.50 inches. Warm advection ahead of an approaching warm front could support lingering low clouds and spotty showers into Tuesday. Temperatures could potentially spike well into the 50s Tuesday, if the region breaks into the warm sector ahead of an upstream cold front. The chance of showers will ramp up ahead of the approaching cold front Tuesday night into Wed. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... Lingering snow showers across NW PA will gradually shift northward and becoming confined to SW NY overnight. Cigs at both KBFD and KJST should remain MVFR overnight, with borderline MVFR/VFR cigs at AOO and UNV. Elsewhere, predominantly VFR conds are expected overnight. Clouds will thicken from west to east on Wednesday as a cold front approaches from the Midwest, with patchy light snow developing across western PA later in the day. The cold front will cross the area Wed night, accompanied by snow showers (possibly mixed with rain across SE PA). This front will usher in a reinforcing shot of cold air along with blustery W/NW winds for Thursday that could gust 30-45 kts. Scattered snow showers and restrictions will continue to impact primarily northern/western PA (KBFD/KJST) on Thursday as well. Outlook... Fri-Sat...IFR/MVFR most likely at KBFD/KJST in scattered lake effect and upslope snow showers. MVFR to low VFR expected elsewhere. Decreasing W/NW winds. Sun...Becoming VFR, with a light southerly breeze developing. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Wednesday afternoon through late Thursday night for PAZ004>006-010-011-017-024-033. Wind Advisory from 1 AM to 7 PM EST Thursday for PAZ004>006- 010>012-017>019-024>028-033>037-041-042-045-046-049>053- 056>059-063>066. && $$ SYNOPSIS...Steinbugl NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/Steinbugl LONG TERM...Fitzgerald/Colbert AVIATION...Evanego