Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Around two feet of heavy snow was deposited at upper elevations on Saturday and conditions were very unstable. Human triggered avalanches will remain likely on Sunday. Stick to traveling on lower angle terrain until this large storm’s snow has more time to settle.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    Observations of several large and very large avalanches in neighboring zones were reported on Saturday. These occurred both naturally and with triggers. The snow was most reactive where wind redistributed the snow into thicker, harder slabs.  Given overnight to stabilize, chances of encountering natural avalanches are decreasing,  but human triggered avalanches are still likely. 

    Only one day out from this large event, continue to be very careful where you travel. Right now it’s best to spend your time sticking to lower angles because the consequences of getting caught in a large avalanche are still too high.

    An example of a large slab avalanche which failed just beneath a cornice. Under cornices are prime spots for wind slabs to form. Photo: Dallas GlassPhoto: Dallas Glas

  • Storm Slabs

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

    In areas where the heavy storm snow isn’t wind affected, it could still remain reactive to a human trigger. If you find any signs of instability such as cracking or a notable “upside down” feeling snowpack, avoid steep slopes in that area, even if they aren’t wind loaded. “Upside down” snow feels punchy, and involves heavier upper layers of snow overlying lighter layers beneath it. The storm on Saturday mostly fell like this, starting out cooler with lighter, drier snow and then getting warmer and heavier as the day progressed. 

    (12/18/2021)

    This small slab avalanche released when a snowcat cut along a trail early Saturday morning as the WSDOT Stevens Pass team assessed conditions in the neighboring Stevens Pass zone. This was very early in the day when the new snow was still quite shallow. 

    Photo: WSDOT

Avalanche Discussion

There is a lot of uncertainty in how reactive the snowpack will remain one day out from the busy day on Saturday. A lot of avalanches occurred in the new snow layer. Staying patient and giving the snowpack a bit more time to heal is a good plan for Sunday.

Régions couvertes