textproduct: State College

SYNOPSIS

* Impactful winter system brings significant ice accumulations to western Pennsylvania, with snow/sleet further east through this evening. * Freezing rain/rain mix Sunday morning transitions to all rain Sunday night. * Strong cold front brings lake effect snow showers, strong winds, and sharply colder temps/wind chills Monday night into the New Year.

NEAR TERM /THROUGH TONIGHT/

KEY MESSAGES: - Wintry mix continues across all of central Pennsylvania this afternoon and evening, with widespread travel impacts expected. - Prolonged threat for freezing rain brings the highest ice accumulation across western Pennsylvania, where an Ice Storm Warning is in effect. - The combination of sleet and freezing rain accumulations across the rest of central Pennsylvania will bring slick conditions for those traveling through this evening, where a Winter Weather Advisory is in effect. -----------------------------------------------------------

An impactful winter system continues to impact central Pennsylvania on Boxing Day (Friday) with a wintry mix ongoing for the entire forecast area as a shortwave trough and low pressure associated with this feature currently stationed over the Midwest approach the region. Model soundings and observations continue to outline an elevated warm nose across all of Central PA, the deepest of which is across western PA. Light to moderate freezing rain has been observed at JST, BFD, AOO, and UNV, with sleet and freezing rain farther east.

Highest ice accumulations expected in the Ice Storm Warning, with slight increases in storm total ice to account for less sleet at onset this morning. A widespread 0.10" or more is expected from Potter County southeast through Lancaster, and totals over 0.25" along and west of the spine of the Alleghenies from Bedford/Somerset north through Clearfield, Elk, McKean and Warren. Latest high-resolution guidance depicts an uptick in precipitation intensity between 3PM to 8PM across our area from northwest to southeast as a shortwave drifts across the region. This could cause freezing rain to changeover to sleet for a bit with more aggressive lift and evaporational cooling of the near-surface layer.

Sleet/snow accumulations generally range between below an inch for the southwestern two-thirds of the forecast area with recent NBM/HREF model guidance bringing a slight increase in snowfall totals across the eastern periphery of the forecast area, where 1-2" of storm-total snowfall is expected. Winter Weather Advisory remains unchanged this cycle. Model soundings do outline some potential for (freezing?) drizzle across the Laurel Highlands and portions of south- central Pennsylvania, but will hold off on inclusion until confidence increases.

The warm air is not far off, with temperatures currently at 50 degrees in Washington, PA. Freezing rain should changeover to rain in western Somerset and Cambria County this afternoon as temperatures warm nicely. We could even see a rumble of thunder or two with more impressive CAPE present thanks to those warmer surface temperatures.

While precipitation types will continue to be important throughout the event, the main take home message will be that slick travel is expected across much of central Pennsylvania this evening and overnight. Temperatures will remain below freezing across most of the area overnight, so even after precipitation ends, untreated surfaces will remain slick.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

Dry conditions are progged by the bulk of model/ensemble guidance on Saturday/Saturday night, before precipitation chances return to the forecast on Sunday as an area of low pressure begins deepening across the Great Lake region. The first mentions of precipitation come near/just after sunrise on Sunday with increasing low-level moisture progged by the bulk of model guidance. Marginal temperatures in the morning/early afternoon hours suggest fair (40-60%) chances for freezing rain mentions at onset between the PA-NY border and the I-80 corridor so have decided to keep FZRA mentions in the forecast at this time. Warming temperatures despite thick cloud cover is expected allowing for a transition towards rain Sunday afternoon/evening with plain rain prevailing through Sunday night. Recent NBM model guidance outlines ice potential north of I-80 with ~40+% members outlining some chances of measurable ice in this timeframe. Further south, lower confidence in any ice accumulation but have retained mentions at this time scale with no thoughts of headlines and relegating any mentions to the HWO with the ongoing system and lack of confidence at this juncture.

LONG TERM /MONDAY THROUGH THURSDAY/

Aforementioned surface low pressure system in the short-term will continue to track a cold front across central Pennsylvania early Monday morning, with cold air behind the frontal passage allowing for a transition back into a rain/snow mix across the northwestern half of the forecast area with rain prevailing further southeast. Westerly/northwesterly flow behind the cold front promotes a combination of lake effect and upslope snow shower mentions across northwestern Pennsylvania through Thursday.

Recent NBM/LREF model guidance paints an impressive signal for gusty winds on Monday after the cold frontal passage with EC/GFS model guidance in fair agreement in a 850mb 70kt LLJ across the Laurel Highlands. Have bumped up wind and wind gusts to the higher end of the ensemble envelope to convey the threat of strong winds. After a mild high in the 40s and 50s on Monday, wind chills will plummet to the single digits and teens by Tuesday morning in the wake of the front.

Cooler temperatures and wind chills also eek their way into the forecast for New Year's Eve and into the first couple days of 2026, we're talking about late December into early January, after all! Minimum wind chills for any outdoor New Year's Eve celebrations will be pushing into the single digits across northwestern Pennsylvania to the upper teens across the Lower Susquehanna Valley. Minimum temperatures by daybreak on New Year's Day range from 0 (NW) to the mid-teens (SE), with slightly cooler temperatures Thursday night into Friday morning.

AVIATION /19Z FRIDAY THROUGH WEDNESDAY/

Precipitation just entering the forecast area at this time. Initial issues will be timing the beginning, and transition, of precipitation in the near term.

Temperatures in the area are below freezing with dry air near the surface. The associated evaporative cooling will keep all precipitation frozen. What type of frozen precipitation will depend on the ultimate thickness of the cold air layer above the ground.

Expect predominately -FZRA over the higher elevations of the west (KBFD & KJST). FZRAPL mainly over the central (KAOO/KUNV/KMDT & KLNS) transitioning to all FZRA. KIPT will begin as -SNPL then transition to PL. All transitions based on the infiltration of warmer air aloft.

Low level winds will be gusty from the southeast. Have added WS wording for winds to 50-60KTS around 2,000 feet AGL through the afternoon. Freezing rain will imply severe icing at the lower altitudes.

Precipitation tapers off generally after midnight from west to east with patchy -FZDZ in its wake as the lower clouds lose their droplet seeding process. Some fog is likely over the higher elevations before improving during the morning hours Saturday.

Outlook...

Sat...Spotty precipitation tapering off.

Sun...Rain with -FZRA possible across higher elevations early, then becoming windy. Restrictions possible.

Mon and Tue...Windy and cold/er with snow showers across the mountains.

CTP WATCHES/WARNINGS/ADVISORIES

Ice Storm Warning until 7 AM EST Saturday for PAZ004-005-010- 017-024-033. Winter Weather Advisory until 7 AM EST Saturday for PAZ006-011- 012-018-019-025>028-034>037-041-042-045-046-049>053-056>059- 063>066.