Avalanche Forecast

A solid overnight refreeze, limited new precipitation, and cooler temperatures will prevent the development of significant avalanche hazard Saturday. You may find newly formed wind slabs on lee slopes closer to the Cascade crest or further north in the region where higher amounts of precipitation occur. If you see fresh cornices, drifted snow, or uneven snow surfaces, expect wind slabs on nearby slopes. You are most like to trigger a wind slab below new cornices, near a convex rollover, or on an unsupported slope. Use your visual clues to identify and avoid these wind loaded features.

Strong refrozen snow and cooler daytime temperatures will delay but not eliminate the development of loose wet surface snow. If the sun comes out, expect the snow surface to change quickly. New rollerballs, fresh fan-shaped avalanche debris, or wet surface snow deeper than your ankle indicate that loose wet avalanches are possible on similar steep slopes. Even though many loose wet avalanches may be small, they can still be dangerous. Loose wet avalanches can carry you into or over slopes that can magnify the consequences of even a small avalanche.

Other spring time hazards exist in the mountains. Cornices have grown large over the past several weeks. As temperatures warm and the sun comes out, these hanging blocks of snow will begin to droop and eventually fail. Additionally, creeks have begun to open, running high and fast with melt-water. Use travel routes and techniques that limits your exposure to both of these springtime hazards.

A dusting of new snow is expected in the Cascade East zones overnight. Locally higher amounts of snow may be seen in areas further north or very close to the Cascade crest. Moderate to strong winds will likely transport this new snow forming new wind slabs at higher elevations. Below 7000 feet this new snow is likely falling on a melt-freeze crust formed over several warm and sunny days. Above 7000’, areas of old drier snow may still be found.

The upper snowpack is quite variable and largely dependent on aspect and elevation. In general, the upper snowpack is a combination of melt-freeze layers, wet melt-form grains, and stronger rounded grains. Locally, you may find preserved layers of weak snow buried in the snowpack. Snow profiles and snowpack tests can assist in finding these potentially weak layers.

We have very limited information about older persistent weak layers on the east slopes of the Cascades. You are most likely to find a reactive persistent weak layer on shaded aspects or at higher elevations above recent rain events. Large cornice failures are the most likely way to trigger such a layer. If you have any information on snowpack conditions consider sharing your observations with NWAC on our public observations page.

Two common persistent weak layers seen in the Northeast Cascades are:

• 3/25 and 3/22: Buried surface hoar layers found on shaded aspects near and above treeline.
• 2/13 Facets above a firm and thick melt-freeze crust can be found in many locations near and above treeline. This layer is thought to be dormant at this time but may re-awaken with a substantial weather input.

Lower elevations further east of the crest have melted back for the season and no longer present an avalanche risk. 

Observations

An avalanche professional traveling in the Stuart Range this week reported a widespread loose wet avalanche cycle Thursday with warm air temperatures and clear skies. Above 6500’ dry snow was still found including lingering wind slabs. This resulted in a skier triggered wind slab on an E aspect at 7800’. Several large and very large (D2-D3) slab avalanches from earlier in the week were also observed.