Bulletin d’avalanche

Summit Lake

Chugach National Forest Avalanche Center
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Danger d’avalanche

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

Points saillants

Wind slab avalanches 1 to 2’ deep could be sitting over a weak layer of snow making them easier to trigger for longer than expected. There is a chance that a wind slab avalanche could trigger a larger avalanche 2 to 4’ deep. Both of these problems become more concerning above 2,500’ on steep wind loaded slopes and where the snow is thin. Keep an eye out for cornices that could fall naturally above you and give them plenty of room on ridges because they can break further back than expected.

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It has been a tragic week of fatal avalanche accidents in the lower 48. In addition to the accident involving a large group outside of Lake Tahoe, there were two fatal accidents in Utah. Our thoughts are with the victims, their friends and families, and all of the responders involved. All investigations are ongoing, but preliminary information may be found at sierraavalanchecenter.org and utahavalanchecenter.org.

Problèmes avalancheux

  • Wind Slabs

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

    Recent Avalanches: What looks like recent avalanches on Summit Mtn were seen yesterday but we are not sure due to blowing winds covering up avlanche debris. It is likely that more natural avalanches occurred during this wind event and have yet to be reported. 

    Strong northwest winds finally began to decrease yesterday evening. We are left with a mostly wind sculpted landscape where the biggest concern is triggering a wind slab avalanche 1 to 2’ deep. These will likely be easier to trigger for longer than expected because they may be sitting over a layer of weak, faceted snow. This setup with a hard slab over weak snow will be a bigger issue above 2,500’ where more snow and wind created larger wind slabs but be on the look out for them at mid elevations as well.  There is also a chance that a wind slab avalanche could fracture a deeper weak layer creating a much larger avalanche (more about this in problem 2). 

    Harder wind slab avalanches can have the characteristic of allowing someone to make several turns before the slope fractures. They typically form below ridgelines, convex rolls, and in gullies. If you find yourself traveling on hard snow (slab) that is on top of soft snow (weak snow), or you see shooting cracks you are likely traveling on a wind slab. Your safest option is to steer clear of steep wind loaded slopes instead looking for wind sheltered snow.

    Cornices could be precariously perched on ridgelines ready to fall as the sun comes out. Be wary of these above you and cautious on ridgelines not to accidentally step on them. They have the tendency to break further back than expected and could trigger an avalanche below you.

  • Persistent Slabs

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

    There is a layer of weak, faceted snow buried 2 to 4’ deep that we have been concerned about for almost two months. Maybe we have trust issues, but it can be hard to trust a weak layer especially when the avalanche could be large and consequential. Over time we have seen less avalanches occurring on this layer and the snow grains seem to be less reactive. We are still wary of thin spots above 2,500’ where it could be easier to trigger a large avalanche. The safer option is to choose slopes without cliffs, trees, and terrain traps where avalanche debris could carry you. 

Régions couvertes