Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A significant winter storm will impact the West South zone Wednesday night and Thursday bringing new snow and strong winds. With stormy weather on tap, this will be a good day to dial it back and stay off of open slopes greater than 35 degrees.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Another round of snow will fall across the West-South zone with strong winds and oscillating snow levels. Some locations may see more than a foot of new snow by the end of Thursday. Expect avalanches to fail within the storm snow due to changes in the wind, temperature, and precipitation rates. Steer around all open slopes greater than 35 degrees. Avalanches may be easiest to trigger during periods of heavy snow or warming temperatures. You could encounter larger more dangerous avalanches on slopes where the wind drifted the snow deeper and at higher elevations. Simple uptrack tests and hand pits may highlight which layer of the storm snow is failing. Often during storms like this, conditions change rapidly. Be leery of applying observations from the morning to slopes in the afternoon. 

    We’ve been talking for several days about buried surface hoar and facets in the West-South zone. So far, we have not received reports of any avalanches on this layer. However, NWAC forecasters continue to find these weak grains in the snowpack. You’re most likely to find buried surface hoar or facets near treeline about 4” (10cm) above the very prominent 12/09 crust. If you see long shooting cracks or feel collapses, seek out low angled terrain well away from steep slopes.

    (12/16/2020) Skin track test showing cracking in the surface snow. This can indicate storm slabs are present.

Avalanche Discussion

While this storm system isn’t huge, it is significant and comes during a long-running active weather pattern that favored the volcanoes. Avalanche danger will be highest in locations that receive more than 10” of new snow. Other sites may experience locally lower avalanche hazard. Expect any avalanche activity to stay above the 12/09 crust layer. This should make observations easy since you can quickly dig down to this layer or even use your probe or poles to feel the snow above it. 

At the lowest elevations, rain and wet heavy snow could produce small loose wet avalanches. Snowpacks on these lower slopes have been through a lot over the past few weeks with warm temperatures and several rounds of rain. This should limit any avalanche activity. Early season conditions continue to weigh on our minds. At lower elevation and on exposed ridges, expect thin coverage and shallowly buried obstacles. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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