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Avalanche Forecast

Archived

Jan 8th, 2020–Jan 9th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Stevens Pass.

Use caution on slopes 35 degrees and steeper and where recent wind drifts have formed at upper elevations. Steer around loaded wind pillows on leeward terrain features near and above treeline. In the past week, storms brought significant snowfall and rain adding stress and new layers to the snow on the ground.

Discussion

Recent avalanches abound! From January 6-7th, a major avalanche cycle occurred in the Stevens Pass area. On Tuesday, brief windows of visibility from Highway 2 yielded upwards of 100 avalanche observations. Seasoned professionals reported numerous avalanches running in places that they hadn't previously observed avalanches. Observers reported that some paths avalanched multiple times in a 24 hour period. Avalanches occurred on all elevations and aspects and were generally large (size D2), 30-50cm deep, and involved recent storm snow. Observers reported a few very large (size D2.5-3) avalanches, originating at upper elevation ridges with deeper crowns that likely formed from wind drifting. On the night of the 6th and morning of the 7th, widespread loose wet avalanches ran up to size D2. Rain fell to at least 5,000ft. on Tuesday. 

Snowpack Discussion

New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.