textproduct: State College

SYNOPSIS

* Lake effect snow showers/flurries taper off by sunrise, giving way to a dry Saturday. * A quick-hitting system will bring snow (north) and a wintry mix (south) late tonight and Sunday with a plowable snow likely across the norther tier of PA. * A more widespread/significant winter storm is possible on Tuesday.

NEAR TERM /UNTIL 6 PM THIS EVENING/

High pressure is beginning to build in early this morning, currently centered over Virginia. A few lingering lake effect clouds and flurries will end by daybreak Saturday. Subsidence associated with rising heights should erode the low clouds during the late morning and early afternoon, but high and mid clouds ahead of our next weather maker will overspread the area during the afternoon. The sun in the southeastern half of the CWA will last thru a good part of the day.

Highs today will still be on the chilly side - ranging from the low 30s in the northwest mountains to near 40 south and east of the I-80/I-99 corridor. Despite the cool temperatures, light winds and some sunshine make today an ideal day to get outdoor holiday decorations hung up or last minute yardwork done if you haven't already (ideal relative to our upcoming stretch of weather at least).

SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/

A strong low pressure system that is bringing significant snowfall across the Midwest today will lift across the Great Lakes on Sunday and drag precipitation across our region. Lift ahead of that system will bring some warm advection snow to western PA after dark. The majority of models and the meso ensembles all make very little precip for the SE third of the CWA on Sunday. What does manage to hit the ground there would likely be a mix in the morning or plain rain from late AM on as temps warm up thru the day. Light snow will be the predominant precip type for the northern mtns. The best QPF is in the NW, too. The first swipe at snow totals there could be near 3 inches in our NW 5-6 counties, and near 2" in the NE. But, that would be the worst of it as the air is very dry with little moisture coming in from the Gulf. Very little signal for freezing rain that lasts more than an hour, but it is worth mentioning inside the broader collection of "wintry mix."

Opted not to issue Winter Weather Advisories yet with lingering uncertainty owing to weak forcing and unimpressive moisture profiles. Regardless, travel impacts are possible north of I-80 on Sunday morning into early afternoon. After a trailing occluded/cold front sweeps through Sunday afternoon, west winds will kick up with gusts 25 to 35mph likely. A few lake effect snow showers are possible in northwest PA Sunday evening into the first part of the night, with another inch or two of accumulation possible. Precipitation will quickly taper off from west to east late Sunday evening into early Monday as high pressure builds in, so Monday should be dry (and not too different from today/Saturday).

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Unsettled weather will continue into the first week of December as cold air in the middle of the country sets up a strong baroclinic zone over the eastern US. High pressure in the Plains should keep cold air in place on the northern side of the precipitation shield from a wave of low pressure progged to move out of the Gulf. This system should move northeast around the base of the aforementioned high pressure system, bringing increasing moisture to the Mid-Atlantic Tuesday into Wednesday.

The system at this time looks to be somewhat progressive with the lack of a strong area of high pressure to slow the advance of the system. Despite the expected fast forward movement, a deepening coastal low could still provide enough forcing juxtaposed with favorable upper jet dynamics to produce significant snowfall across the region. Snow looks to arrive later Monday night and lift across the region during the day on Monday. The eventual track and intensity of the low will have big implications on observed snowfall totals and the northward extent of any mix/rain scenarios.

The latest WPC probabilities of 0.25" or greater liquid equivalent snow/sleet paint medium probabilities (40-70%) across most of the region, with slightly lower amounts expected in northwest PA. The latest Winter Storm Outlook highlights a 30-50% chance of Warning criteria snowfall (5"+) in northeast PA. GEFS and ECENS probabilities of 6"+ continue to outline probabilities <30% with a higher likelihood in northeast PA up through coastal New England. If confidence increases in higher amounts, Watches may be needed in the next 24-48 hours. At this time, though, a plowable snowfall seems like a reasonable bet for most of the region. Continue to monitor the forecast in the days ahead, especially if you have plans to travel.

Later in the week, high pressure will regain control of our weather. Prevailing upper troughing brings high confidence in continued below normal temperatures and a chilly start to December. Low temperatures in the teens or single digits are possible and our active storm pattern appears likely to continue.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

Bands of snow showers over northern PA will continue to weaken today. A few snow showers and flurries will be around the area early on today. Conditions will trend toward VFR conditions later today.

Winds shift to the southeast later this evening, as a warm front moves toward western PA.

The leading edge of the snow will be across the west on Sunday around 12Z, mainly at BFD and JST at that time.

The far southeast areas like MDT and LNS may not see pcpn until later in the day on Sunday.

Outlook...

Sun...Light rain/wintry mix developing from west to east; restrictions possible. Precip may turn to rain across the south during the day.

Mon...Mixed/wintry precip likely early on. MVFR likely. IFR possible.

Tue...Snow possible, before a possible mix later in the day across the south. Restrictions possible.

Wed...Trending drier, lingering snow across NW PA.

CTP WATCHES/WARNINGS/ADVISORIES

None.