Avalanche Forecast
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.
Avalanche Problems
Storm Slabs
You may be able to trigger avalanches where recent snow has accumulated in the past 24 hours or where you find lingering storm layers from the past couple of days. Avoid convex slopes and unsupported features. Use caution around slopes steeper than 35 degrees. Watch for stiffer snow, overlying softer snow. Use small test slopes and snowpack tests to look for recent storm layers in the top 2 feet of the snowpack. Wind has formed deep drifts on leeward sides of ridges at the highest elevations. Avoid deeply drifted features and leeward start zones.
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1