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Avalanche Forecast

Archived

Jan 7th, 2020–Jan 8th, 2020

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

Regions

Stevens Pass.

Use caution near slopes 35 degrees and steeper especially above 5,000 feet. Give the snowpack another day to adjust before venturing into big terrain. Over the past 4 days, a storm 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. While temperatures cool, you may still find wet or moist snow at low elevations.

A very large avalanche (D2.5) with a deep crown on Rock Mountain, southeast, 6,000ft. 1/7/2020. Photo: Josh Hirshberg

Snowpack Discussion

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

Problems

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.