Bulletin d’avalanche

Olympics

Northwest Avalanche Center
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Danger d’avalanche

Mon
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

You can trigger a small wind slab that may propagate more widely than you expect near and above treeline. Fresh higher density snow transported by the wind will load lower-density layers to create unstable slabs that you can trigger on steep, convex slopes in the lee of ridgelines.  Early season conditions have returned following a mild December start - watch for shallowly submerged obstacles throughout the terrain.

Problèmes avalancheux

  • Wind Slabs

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

    Small wind slabs will build throughout the day as 2-6" higher density snow (0.25-0.5" of water equivalent) falls on and gets redistributed by decreasing light to moderate winds. These wind slabs will sit on 1-2" of lower density snow, which may have some near-surface faceting, and sits on a stout crust. While they may be shallow , expect wind slabs to propagate and run farther than you expect. You can trigger the wind slabs on steep, unsupported slopes or wind-loaded slopes near and above treeline. If we get toward the lower end of our water numbers, winds may still move the low-density snow around, but slabs will be isolated to very steep or extreme terrain. Check for the presence of >6" snow above a crust. Observe for signs of instability as you ascend in the terrain such as cracking, or settling of the snow under your feet as you travel. Check the bond between the new and the old snow. When in doubt, stick to slopes less than 35 degrees and avoid wind-loaded slopes.

    (12/12/2020) Example: Small wind Slab on the north side of Chair Peak that swept two travelers off their feet.

Avalanche Discussion

The Olympics got off to a strong start with snow depth reaching 33" at Hurricane Ridge by December 1st.  Nearly a week of high pressure, featuring sustained above-freezing temperatures, ended with a warm, wet system December 7-8 soaked the upper snowpack with 1.5" of water, most of which fell as rain and ended with a skiff of new snow as temperatures cooled below freezing and then refroze the upper snowpack, limiting avalanche concerns below this layer. The Olympics then picked up 1-2" of fluffy snow either Wednesday or Friday. Winds loaded an extra few inches of snow into lee locations, but this has not been enough snow to create avalanche concerns. That will change with the addition of more and denser snow with wind late Saturday night and Sunday.

Warm, windy, and wet weather over the past week took its toll on the snowpack significantly eroding cover on steep southerly slopes and along exposed ridges. You may notice many obstacles reemerging. Give yourself extra time to deal with the challenging conditions and navigating around obstacles.

2020-21 Forecast Schedule: Avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays. During the week when the Hurricane Ridge road is closed, forecast information will be updated daily to include expected conditions and relevant travel advice under the No Rating label.  

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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