Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Very warm and sunny weather could cause the snow surface to become wet and unstable on Wednesday. This may occur quickly at mid and lower elevations where more soft snow exists. If you see new rollerballs or fresh fan-shaped debris, steer around similar slopes.

Avalanche problems

  • Loose Wet

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

    The warm sunny weather should quickly start to change the snow surface causing it to become wet and unstable on Wednesday. Near and below treeline, plenty of softer non-wind-affected snow could result in more widespread and larger avalanche activity on a variety of aspects. At upper elevations, recent very strong winds formed firm and scoured surfaces that will take longer to succumb to the spring-like weather. With freezing levels forecasted to soar to 8500', only the highest shaded slopes may possibly escape this warm-up. 

    Simple clues can help you figure out when the snow has become unstable and possibly dangerous. If you see the snow shedding from rocks/trees, find new rollerballs, or notice fresh fan-shaped debris anticipate loose wet avalanches. Some of these slides could occur naturally from the slopes similar to those where you see these observations. Steer around steep terrain where you see signs of possible wet slides. Remember to pay attention to the terrain above you. It could sit in the sun even while you travel in the shade.

    (3/28/2021) Loose wet avalanches like these on the NE aspect of the Castle (Tattoosh Range, Mt Rainier) show the power of the sun to reach all but the due north faces in the springtime. 6300', NE, The Castle.

Avalanche Discussion

Recent weather patterns created quite a bit of variability around the West South zone. Some locations experienced more sunshine, stronger winds, or deeper snowfall. These differences can occur over much smaller scales than we’re used to such as from one basin to the next. Continually make observations to help highlight when you are encountering different conditions. Most areas around the region received 10-15” of snow along with very strong and sustained winds Sunday/Monday. At upper elevations, this resulted in scoured crusts, wind-packed snow, and deep drifts. In more sheltered terrain the new snow fell on a recent crust (3/28). If loose wet avalanches fail this firm smooth interface they could run far and fast. 

Below the surface, a relatively aspect-dependent upper snowpack exists. In shaded terrain, thinner crusts interspersed with layers of strong dry snow form a well-settled and more winter-like structure. On southerly aspects, thick well develop layers formed during several melt-freeze cycles resulting in very strong snow. Despite the spring-like weather, the snowpack has not fully undergone this transition. 

In some locations, large cornices formed during the recent stormy weather. You could see some of these fail during Wednesday’s warm weather. Choose routes that limit the amount of time you need to spend traveling underneath these looming hazards. Falling cornices or small loose wet slides could serve as triggers for slabs especially in wind-loaded or rocky terrain. 

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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