textproduct: State College

WHAT HAS CHANGED

* Extreme Cold Watch upgraded to an Extreme Cold Warning for areas along and north of I-80 and along and west of I-99. Cold Weather Advisory for the rest of the area. * Wind Advisory issued for much of Central PA.

KEY MESSAGES

1) A clipper system will bring a coating to a couple inches of light, powdery snow to much of the area today, leading to slippery travel; higher amounts in the Laurels.

2) Blustery with dangerous wind chills Friday night through Sunday morning; coldest weekend of winter

3) Moderating temperatures during the second week of February

DISCUSSION

KEY MESSAGE 1: A clipper system will bring a coating to a couple inches of light, powdery snow to much of the area today, leading to slippery travel; higher amounts in the Laurels.

Light snow will move in from west to east this morning. A secondary shot of snow/snow showers later this afternoon/evening will be driven by a strong arctic frontal passage followed by plummeting temperatures and blustery winds into Saturday morning. Although moisture will be modest in an environment with well below normal PWs, the orographic/upslope forcing/ascent into a deepening DGZ will be sufficient to wring out a moderate to locally heavy (fluffy) snowfall in the Laurel Highlands. A higher-end winter weather advisory has been issued for Cambria and Somerset Counties based on a combination of snow, wind, and blowing snow preceding extreme cold. The usual summits and ski resorts along Laurel Mtn could pick up as much as 6-8 inches of high SLR fluff. Elsewhere along the Allegheny Plateau, a general 1-2" is expected with a 0.5-1" most likely in the central and southern ridge/valley region. We still can't rule out a couple of heavier snow showers or brief squalls along the arctic front, but instability should be limited with the front arriving near or just after sunset.

KEY MESSAGE 2: Blustery with dangerous wind chills Friday night through Sunday morning; coldest weekend of winter

Prepare for the coldest weekend of winter with wind chills 20 to 30 below zero possible/likely early Saturday morning. We have issued an Extreme Cold Warning for areas along and north of I-80 and west of I-99. The rest of the area is under a Cold Weather Advisory. The lowest wind chills occur early Saturday morning, but remain below zero through Saturday afternoon before dropping back to double digits below zero Saturday night into early Sunday morning.

A very tight pressure gradient across the region behind the arctic front will support wind gusts in the 40 to 50 mph range on Saturday. Strong pressure rises behind the front will lead to gusts as high as 55 mph during the morning over the Laurel Highlands. A Wind Advisory has been issued for most of Central PA from midnight tonight through 10 PM Saturday. Winds remain gusty on Sunday, but should stay below advisory strength.

KEY MESSAGE 3: Moderating temperatures during the second week of February

For those looking for a break in the cold pattern, here you go. Confidence continues to increase that temperatures will moderate during the second week of February and climb back to seasonal levels or near the historical average for early to mid February. This "warmup" puts mixed precipitation on the table with the next weather system that could arrive Wed/Thu next week. The guidance has come into better agreement concerning the precip pattern evolution with best odds around the middle of next week.

AVIATION /09Z FRIDAY THROUGH TUESDAY/

Bulk of model guidance continues to track low-level stratus with bases 1500-2500ft AGL closer to 06/09Z as a clipper system approaches the area. Light stratiform snow will break out across central PA after sunrise, with max coverage during the afternoon. Guidance generally keeps ceilings 1000ft AGL or higher through much of the day, with some potential for lower ceilings at BFD/JST after 06/18Z. BFD/JST has the highest chance of IFR ceilings (~60%-70%) in the late afternoon and evening. Visibility will likely range from 3/4SM to 4SM in light snow across the area. Stratiform snow will dissipate across the west towards 00z Sat, as snow showers along and behind the Arctic Front. Across east-central Pennsylvania, stratiform light snow will continue later into the night, with ending time closer to 07/02Z.

Winds will increase and stay strong through the day Saturday with gusts 35-45 kts. This may result in areas of blowing snow reducing vsby into the day Saturday even after the snow ends. Winds slowly decrease later Sunday.

Outlook...

Sat...Sct SHSN/MVFR AM (IFR poss) BFD/JST. Strong NW wind.

Sun...-SN/MVFR poss W. VFR E.

Mon-Tue...No sig wx.

CTP WATCHES/WARNINGS/ADVISORIES

Extreme Cold Warning from 1 AM Saturday to 10 AM EST Sunday for PAZ004>006-010>012-017>019-024-025-033-034-037-041-042-045- 046. Wind Advisory from 4 AM to 10 PM EST Saturday for PAZ012-027- 028-036-041-042-045-046-049>053-056>059-063>066. Wind Advisory from midnight tonight to 10 PM EST Saturday for PAZ017>019-024>026-033>035. Winter Weather Advisory from 10 AM this morning to 7 AM EST Saturday for PAZ024-033. Cold Weather Advisory from 4 AM Saturday to 10 AM EST Sunday for PAZ026>028-035-036-049>053-056>059-063>066.