Bulletin d’avalanche

Seward and Lost Lake

Chugach National Forest Avalanche Center
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Danger d’avalanche

Tue
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 7 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Travel in avalanche terrain is not recommended. There is a high likelihood of triggering a very large and destructive avalanche, even from low-angle terrain connected to steeper slopes. The snowpack is very unstable and dangerous right now, and we need to give it more time to heal before entering avalanche terrain. We have issued a Special Avalanche Bulletin through the National Weather Service to help spread the word about the unusually dangerous conditions. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    East winds have been steadily moving snow onto leeward slopes for the past few days, forming wind slabs 1 to 2' deep that could be triggered by a person today. You can keep an eye out for hollow feeling pillows of windblown snow or shooting cracks near ridgelines and convex features to help identify wind slabs. Triggering a relatively small wind slab avalanche could initiate a larger avalanche on a buried weak layer.

  • Persistent Slabs

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

    Recent avalanches: We received secondhand reports of multiple natural and human-triggered avalanches in the Lost Lake area on Friday, some of which were very large, and at least one where someone rode off of a moving slab. We also documented widespread natural avalanche activity from Moose Pass to Seward, with wide-propagating avalanches running to valley bottoms.

    This is the third day since the major storm ended, and we still have the avalanche danger at high because the chances of a very large human-triggered avalanche that could bury a person are high. Our current snowpack setup is incredibly dangerous, with a buried weak layer of facets causing avalanches 2 to 4' deep that can be triggered remotely from low-angle terrain below steeper slopes. These avalanches could easily be triggered on slopes that are typically safe a few days after a storm. This type of snowpack setup may allow several tracks on a slope before someone finds the weak spot and triggers an avalanche. 

    This type of persistent slab setup takes time to heal and requires patience to safely manage. The only reliable way to avoid triggering a very large avalanche is to stick to simple terrain. Which means travelling in areas where the slope angle is below 30°, there is no steep terrain above that is connected and could be triggered from below, and avoiding terrain traps like gullies and cliffs where triggering even a small avalanche could have severe consequences. Don't get fooled by the quiet weather—conditions are primed for an avalanche accident.

    Special Avalanche Bulletin messaging the high likelihood of very large human-triggered avalanches. 

    Photo: NWS Anchorage

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