textproduct: State College

WHAT HAS CHANGED

* Winter Storm Warning remains in effect for the Laurel Highlands; all other winter headlines have been cancelled

KEY MESSAGES

1) Breezy with an additional 1-3 inches of snow over the Laurel Highlands through early tonight

2) Quick-hitting minor to plowable snow accumulation Tuesday night into the Wednesday morning commute

3) Mixed/wintry precip likely Thursday into Thursday night

DISCUSSION

KEY MESSAGE 1: Breezy with an additional 1-3 inches of snow over the Laurel Highlands through early tonight

Seasonably cold NWly/upslope flow on the backside of mature Nor'Easter blizzard will continue to drive lake/terrain enhanced snow showers across the western Allegheny Plateau into the Laurel Highlands into tonight. Expect an additional 1-3" of snow through early tonight with the highest amounts on the ridgetops and summits to the west of US-219.

Gusty winds 25-35 mph will produce some areas of blowing and drifting snow before gradually subsiding into Tuesday. Wind chills will drop into the negative single digits over the western and northern mtns overnight.

KEY MESSAGE 2: Quick-hitting minor to plowable snow accumulation Tuesday night into the Wednesday morning commute

A clipper system tracking from northern MN through MI into Upstate NY will bring warm advection snow Tuesday night through Wednesday morning. Lake and orographically enhanced snow showers likely continue to impact the western Allegheny mtns Wednesday afternoon into Wednesday evening. The best odds for plowable (>2") snowfall is along and north/west of the I99/I80 corridor. The snow and slippery road conditions would likely impact the Wednesday morning commute and may result in travel/school delays. KEY MESSAGE 3: Mixed/wintry precip likely Thursday into Thursday night

Late week system tracking across the Mid-South toward the Northeast U.S. has the potential to bring a broader area of mixed/wintry precip Thursday-Thursday night. A band of sleet or freezing rain is possible in the transition zone between snow and plain rain. The details (ptypes, amounts) are still highly dependent on the low track, with the best odds for plowable snow across the northern tier (near and north of I-80) and best chance for ice/rain from the PA Turnpike south to the MD line.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

Cold air aloft, shallow low-level moisture, and northwesterly winds continue to fuel lake-effect snow showers across KBFD and KJST, with KUNV and KAOO occasionally observing -SN as well. The NAM and RGEM are handling the longevity of these snow showers relatively well, and are depicting that snow showers will slowly taper off through roughly 12z-15z. Alternating MVFR/IFR visibilities are occurring with these snow showers at KBFD and KJST, which will most likely continue through 09z, with gradual improvements to VFR visibilities expected afterwards.

An MVFR cloud deck persists across the areas seeing snow showers and flurries, which will most likely hold through the morning. During the daytime, sunlight will help to raise cloud ceilings and break up this deck of clouds via surface heating and boundary layer mixing. VFR is likely across all airports by the afternoon / early evening, including KBFD and KJST, despite a more gradual rate of improvement expected due to their proximity to the lakes.

The forecast becomes complex between 00z and 06z as a clipper system moves across the Great Lakes and into the Northeast, bringing a potential round of snowfall along the leading edge of the system. At this range, models are sometimes too slow with the arrival of snowfall, generally lagging a few hours behind. And so, a PROB30 of -SN with MVFR/IFR visibility restrictions was introduced across all airports within the last few hours of the TAF, with the HRRR being preferred for timing due to its earlier onset compared to other models.

Outlook...

Tue...MVFR-IFR restrictions possible in snow showers at BFD/JST, largely VFR elsewhere.

Wed-Fri...Restrictions possible in rain/snow showers.

Sat...Mainly dry with VFR conditions possible.

CTP WATCHES/WARNINGS/ADVISORIES

Winter Storm Warning until 9 AM EST this morning for PAZ024- 033.