textproduct: State College

SYNOPSIS

* Light snow over the northwest Alleghenies and Laurel Highlands this afternoon/evening comes to an end by late tonight * Cold day on Monday precedes bitterly cold to frigid conditions Monday night into Tuesday morning * Brief thaw Wednesday allows for mixed precip followed by an arctic resurgence and enhanced snow/wind chances late week

NEAR TERM /THROUGH TONIGHT/

IR sat loop shows widespread low cloud cover blanketing CPA early this morning. These clouds are holding temps several degrees warmer vs. NBM/prev fcst.

Northern stream trough tracking across the Great Lakes into northern New England will bring light snow to the NW Alleghenies during the afternoon into the first part of tonight. The synoptically forced snow will end as lake effect snow showers early tonight. Snowfall amounts continue to trend lower with <1" now fcst along parts of the Allegheny Front.

Much colder air will filter into the area tonight as modified arctic high migrates eastward from the Upper Midwest. Low clouds could linger in the northern tier and over the Laurels while other locations partially clear out. Min temps are fcst in 10-20F range for most of the CWA with single digits possible in the NW mtns.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

1030mb high migrating over CPA will ensure dry and cold wx on Monday. Daytime highs are fcst to stay below the freezing mark.

A quick moving 500mb trough will track from the TN Valley to the Southeast Coast by Monday afternoon. While this system will not impact CPA, model trends have brought snow much farther north into the WV/MD panhandle.

Monday night looks bitterly cold to frigid with lows in the 0-15F range. Dewpoints at KBFD would favor a subzero minT print; however western sites could bottom early and trend neutral to non-diurnal as the sfc ridge axis slides to the east of the Allegheny Front and Blue Ridge Mtns by 12Z Tue. Quick check of daily record low temps does not sound any alarms, but there may still be some room to the downside in the fcst.

High pressure shifts east of the I95 corridor by Tuesday afternoon as another low amplitude northern stream trough traverses the Great Lakes. Weak lift and WAA ahead of this disturbance could brush the NW part of the CWA with another light snowfall (<1") by 00Z Wed.

By Tuesday night, an intense mid-980s mb clipper low will be racing through WI and into MI by Wednesday morning. WAA out ahead of this anomalously deep, more intense than most clipper (by historical/climatological MSLP standards) is expected to spread accumulating light snow (C-2") across the NW 1/2 of the CWA for the Wednesday morning commute. Mixed ptype issues appear likely initially along the southeast flank of the precip shield.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

The strong clipper low tracks up the St. Lawrence Valley on Wednesday. Gusty SW flow transports milder air into CPA resulting in a brief thaw and rain/wet snow or all rain ptypes with highs 35-45F.

Cold front trailing the low will move through Wednesday night, allowing much colder air to return to the forecast area behind a blustery NW flow. This will trigger lake effect/upslope snow into Thursday. Max wind gusts will likely trend higher at shorter ranges.

Another vigorous 500mb shortwave trough and clipper system take aim on the area late in the week with a reinforcing shot of arctic air into the weekend. Odds for potential snow and wind impacts are elevated with obvious timing uncertainty at this forecast length.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

MVFR/low-end VFR stratus continues to expand southeastward and now blankets all of central Pennsylvania. n area of low pressure will track north of Pennsylvania during the day, bringing snow showers into northern and western parts of the state for the afternoon. Ceilings will likely drop to IFR at BFD and JST as the system approaches. The best chance for snow will be at BFD, potentially leading to a period of IFR visibility, but some guidance suggests that the snow showers could make it as far southeast as UNV (<10% chance).

Snow comes to an end between 00Z-03Z Monday as high pressure quickly builds in behind the system. Skies will first begin to clear out for the southeastern terminals as a downsloping northwest wind develops after 00Z, and a trend toward VFR conditions will continue across the rest of the airspace into the early morning. Winds will increase to around 10 knots with a few gusts to 20 knots at IPT, MDT, and LNS.

Outlook...

Mon...Mainly VFR

Tue-Thu...Restrictions possible with snow or mixed ptype, especially across the northern half of Pennsylvania, as multiple low pressure systems track through the northeastern US. Gusts 20-30 kts.

CLIMATE

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

CTP WATCHES/WARNINGS/ADVISORIES

None.