Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Recent numerous avalanches were the result of significant changes in the snowpack, which may still be adjusting. Avoid terrain features where the wind has drifted the snow into deeper piles and keep an eye out for clues of unstable snow such as shooting cracks or whumpfing collapses.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    If you find yourself playing in the cold and dry snow on Saturday, don’t forget about the large number of natural and human triggered avalanches we just experienced this past week. It's in these areas where you need to be aware of piles of wind-deposited snow where you could trigger an avalanche more easily. Winds often deposit snow on the sides of gullies, the base of cliffs, and on leeward slopes, including convex rollovers. Textured snow surfaces and freshly built cornies can help you determine which way the wind was blowing and where to identify these features to steer around. Take the time to dig down and look at the snow for potential weaknesses before committing to terrain, even in areas where you do not see any signs of wind-effect. If you find that the snow is failing easily in your test pits, there is heavy snow over weak snow, or you notice red flag signs of instability such as shooting cracks and whumpfing collapses as you travel, avoid similar slopes over 35 degrees. 

    (1/7/2021) A subtle weak layer was found approximately 40cm down in multiple locations around the Crystal Backcountry on Thursday. You need to look for layers of concern in the upper snowpack wherever you decide to travel on Saturday.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Saturday should be a relatively nice day in the West South with the sun making an appearance for at least some of the day. We’re not sure if there will be enough of a window of sunny weather to drive a Loose Wet avalanche problem, but it should be on your radar, particularly in areas further away from the crest such as the volcanoes. If you find yourself in the sunshine and notice fresh rollerballs or snow shedding from trees and rocks, head for shadier slopes and be aware of the terrain above you. Loose Wet avalanches may be difficult to get moving, but once they do, they can entrain lots of snow and grow very large, even triggering slabs as they descend.

    (1/1/2021) Rollerballs on the Valley Rd near Paradise, Mt Rainier National Park. Clues like this indicate the surface snow is becoming wet and unstable.

Avalanche Discussion

It has been a few days since our last big loading event but we aren't in the clear, yet. Don’t ignore the large number of avalanches that just occurred throughout the zone and the changes the snowpack has been through. Conditions are still primed for large human triggered avalanches and the possibility remains that some of these avalanches could grow very large and destructive (D3). These very large slides could be categorized as low likelihood, high consequence. But now that you know the danger, it’s up to you to make good decisions not only for your own group but those traveling around and below you. There remains a lot of uncertainty around this snowpack and what it could take to trigger some of these deeper layers. What we do know is that after receiving so much recent snow, triggering even a small avalanche could potentially create larger and more destructive avalanches by activating deeper layers or through entrainment. 

When you’re digging on Saturday to make your own assessment, take a look for the 1/1 crust approximately 80-100cm down from the surface and really study the snow above it. We believe that any slides on Saturday should occur above the 1/1. But if that doesn’t satisfy your curiosity, you can dig a little deeper to the prominent 12/21 crust to get the full picture of what we have received for snow in the last ~10 days. NWAC professionals on Thursday were in the Crystal Mountain backcountry and found a layer of concern approximately 40cm down that continuously failed in stability tests. This is an example of one of many potential weak layers throughout the zone that you need to be aware of on Saturday and you will need to take some time to find these layers for yourself.

Other dangerous conditions may exist on Saturday as you travel in the mountains. Creeks are running high at lower elevations, large amounts of snow and branches are falling from trees, and the deep snow creates a hazard due to tree wells and deep snow immersion. Find out more information about deep snow safety HERE.

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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