A new winter system moved in as a trough dropped into the Pacific Northwest on December 21st. With the accompanying atmospheric river, this system had substantial moisture with it bringing a wet and windy day ahead. Most of Eastern Washington was still too warm for snow, but there was moderate snowfall in the east Cascade slopes. Throughout the remainder of the region, locations received 24 hour rainfall totals up to 0.5 - 1.0.
In addition to wet conditions, the evening of the 21st into the early morning hours of the 22nd were windy, with damaging winds in the Palouse. The strongest winds were in far Eastern Washington, from Spokane to Pullman, and Cascade slopes. There were sustained winds 20 - 30 mph with gusts to 35 - 50 mph for over a 12 hour period. It was windy for much of the region, but much lighter with gusts to approximately 20 mph. Numerous power outages occurred in Chelan, Whitman, and Stevens counties.

Heavy Snow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 20-DEC-20 22:00:00 to 21-DEC-20 09:50:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A CoCoRaHS observer, 3 miles southeast of Winthrop, recorded 7.1 inches of new snow accumulation.

Heavy Snow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 20-DEC-20 20:00:00 to 22-DEC-20 07:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A CoCoRaHS observer, 6.8 miles north-northwest of Winthrop, recorded a 48 hour total snow accumulation of 12.5 inches.

Heavy Snow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 20-DEC-20 20:00:00 to 21-DEC-20 14:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A member of the public, in Twisp, reported 7.0 of new snow accumulation.

Heavy Snow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 20-DEC-20 22:00:00 to 21-DEC-20 14:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A member of the public, in Winthrop, reported 8.0 inches of new snow accumulation.

Heavy Snow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 20-DEC-20 22:00:00 to 21-DEC-20 14:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A member of the public, in Mazama, reported 9.0 inches of new snow accumulation.

Strong Wind in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 21-DEC-20 21:00:00 to 22-DEC-20 02:00:00 (PST-8)
Magnitude: 36.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Utility Company

There were sustained winds 20 - 30 mph with gusty winds to 55 mph in the eastern slopes of the Cascades. Local utility companies reported 1,200 people in Chelan County without power due to large trees falling on power lines.

High Wind in LOWER GARFIELD & ASOTIN, WASHINGTON
From 22-DEC-20 00:00:00 to 22-DEC-20 02:00:00 (PST-8)
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

The RAWS site at Alder Ridge measured wind gusts to 61 mph.

Heavy Snow in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 20-DEC-20 22:00:00 to 21-DEC-20 14:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Numerous locations across the Methow Valley, in Okanogan County, received heavy snowfall in this winter storm. There were reports of 24 hour accumulations of 7 to 9 inches, as well as 48 hour reports of 12 to 14 inches.

Strong Wind in WASHINGTON PALOUSE, WASHINGTON
From 21-DEC-20 23:00:00 to 22-DEC-20 01:00:00 (PST-8)
Magnitude: 48.00 MG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Gusty winds were measured to 55 mph at the Pullman/Moscow Airport. Pullman city law enforcement reported large trees down and two power poles broken with lines hanging. This left approximately 2,300 people without power and numerous road closures in Pullman.