textproduct: State College

SYNOPSIS

* Fair, generally dry weather is expected into tonight with lower wind gusts * A period of accumulating snow is expected from late Saturday morning into early Sunday, followed by another Arctic blast and locally heavy lake effect and upslope snow across NW PA * Windy Sunday into Monday * Signs of a warmer pattern change on the horizon by the middle of next week

NEAR TERM /THROUGH TONIGHT/

We had a good amount of sun earlier, but widespead cloud cover now as of early aft. A few small bands of flurries and very light snow showers still possible the next few hours, but expect the rest of today and tonight to be dry. Clouds will taper the low temperatures tonight some.

SHORT TERM /SATURDAY THROUGH MONDAY/

Main changes was to upgrade the watch across the northwest to a warning. I did trim the southern edge of the higher snowfall numbers a bit on the south side.

Other area of concern was the upslope areas of the Laurel Highlands, where a winter weather advisory in effect. Highest amounts expected across the western edges of those counties.

Slightly less snow for Clearfield Coounty, but an advisory there and also for nearby counties. Winds and cold, so impacts a factor as well as the snow.

Snow being the result of a fast moving cold front and strong jet dynamics. Low pressure forms but will race off the coast, so to limit snow to the southeast.

Directional shear likely to result in a delay in the more organized lake effect setting up. Also upslope snow will be a factor into the southwest. Low level flow may be too much from the north early on to support the lake effect.

Later Sunday into early Monday, wind and cold will be a factor.

Still looking at the potential for snow across the southeast, still several periods out.

More information below.

Max temps Sunday will drop by 10-20 degrees vs. Saturday with mean departures from climo on the order of 15 to 25 degrees. A few locations could see highs close to the daily record low max. Gusty winds and very cold temps will send min wind chills near and below zero Saturday night through Sunday night/AM Monday.

Lake effect/upslope snow showers continue through Sunday night.

LONG TERM /MONDAY NIGHT THROUGH THURSDAY/

Winds by Tuesday shift more to the west, then to the southwest by Wednesday, as a large high pressure system moves eastward to the southeast states. The large scale flow pattern becomes more zonal, as upper level heights rise to much higher values than we had seen lately. This will set the stage for temperatures climbing to above normal, at least for the period Wednesday into late Thursday.

A cold front by Friday will edge things back down some, but not the really cold that has been typical this month so far. The month has been nearly 10 degrees colder than normal up to this point, which is nearly half of December.

Earlier discussion below.

One more shortwave trough could brush the area with light snow early next week; otherwise there is growing confidence in a mid to late December thaw as the pattern transitions to a milder SW flow aloft with mean troughing shifted westward into the Central U.S. Dry wx is favored Tue-Thu with highs climbing toward the 40-50F range late in the week - possibly in advance of the next widespread precip event.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

MVFR clouds re-established over wrn and cent mtns, but have begun to recede from the east in past 2hrs. Wind should be getting lighter through the aftn and evening, and nearly calm overnight. Wind will increase slightly on Sat. Clouds will thicken up from the west early in the AM, with light to mdt snow hitting the ground in the western highlands (esp JST) before noon local/17Z. L/IFR in SN will spread east and affect all of the area Sat aftn and night, but end in IPT/AOO/UNV first (by midnight local (05Z). JST will be LIFR for a 3-6hr period as they should have the steadiest snow of any of our terminals for the longest time Sat aftn/evening. IFR may (50%) linger closer to sunrise in the SE (MDT/LNS) with the worst conditions there between 04Z-09Z. LNS will likely be worse than MDT with the heaviest snow falling to our SE (Philly/DC). It will get windy on Sun and into early Sun night as very cold air moves in. The western terminals (BFD and JST may (40%) have a few hour break Sun AM before lake effect kicks back in, and cigs/vsbys drop again Sun late AM/aftn.

Outlook...

Sun...SHSN/IFC linger in western highlands. MVFR cigs/isold SHSN AOO/UNV. MVFR/VFR cigs elsewhere. Gusty west wind.

Mon...MVFR w/sct SHSN BFD, no sig wx elsewhere.

Tue-Wed...No sig wx.

CLIMATE

Astronomical winter (solstice) begins at 10:03 a.m. on Sunday, December 21st.

CTP WATCHES/WARNINGS/ADVISORIES

Lake Effect Snow Warning from 10 AM Saturday to 7 AM EST Monday for PAZ004-005. Winter Weather Advisory from 10 AM Saturday to 7 AM EST Monday for PAZ010-017-024-033.