Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Dangerous conditions will develop initially at upper elevations where wind slabs will increase in size and reactivity throughout the day. The marked increase in avalanche danger requires a commensurate shift in mindset. Dial back your terrain selection as the storm intensifies. Avoid all slopes steeper than 35 degrees near and above treeline or where 8" or more of fresh snow forms storm slabs in less wind-affected terrain.  

Problèmes avalancheux

  • Storm Slabs

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

    We're expecting a good helping of snow, likely 10-12" by the end of the day on Tuesday. Storm slabs will build during the day and may not be reactive until the afternoon as intense snow piles up to create instability. Sheltered terrain will harbor more pleasant snow, but also storm slabs. Use your pole or probe to feel for firmer snow under the fresh snow and if that interface is 8" or deeper, expect reactive storm slabs. You're most likely to trigger a storm slab on a convex rollover steeper than 35 degrees. 

    (12/16/2020) Example: Storm slab.

  • Wind Slabs

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

    Moderate to strong winds are ready to transport snow, but they won't start building slabs until the snow starts flying late Tuesday night. Expect slabs to build rapidly at upper elevations as the storm intensifies on Wednesday and some will rapidly increase into the large size range. Some of these slabs could be firm and break widely. You'll be able to key in on signs of active snow transport, cracking of the snow surface, and fresh cornice formation to confirm the problem. Given the strength of the winds, your best plan is to retreat to sheltered terrain or lower-angle slopes rather than trying to avoid wind-loaded slopes. These wind slabs will build on generally firm surfaces, so expect this to provide a bed surface for avalanches to run on. Avoid all slopes steeper than 35 degrees near or above treeline.

     

     

    (12/26/2020) Hard slab 1.5-2.5 ft thick, running on 12/21 crust at Crystal Mountain, WA.

Avalanche Discussion

Given the wind-loading we expect at upper elevations during this intense storm, the very large natural avalanches triggered on northerly aspects a week ago remain in the back of our minds. Check these out in the media galery. Practice safe transition points that are not exposed to large slopes from above.

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.

Régions couvertes