Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

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

Points saillants

Very dangerous avalanche conditions are expected to continue for above treeline elevations and the threat of natural avalanches will grow this afternoon. A natural avalanche initiating at upper elevations could become very large while pushing far into its avalanche path. The threat of those natural avalanches decreases slightly at lower elevations, while human triggering remains a very real problem. Cautious route-finding and conservative terrain selection are imperative today. 

Problèmes avalancheux

  • Persistent Slabs

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

    Slab avalanches breaking into persistent weak layers around the compass remains problematic. These avalanches could release in the middle, or at the bottom of the snowpack. In some areas, primarily on slopes facing NE to SE, this avalanche problem is on a hair-trigger where slabs are resting above very weak faceted snow. The characteristics of this avalanche problem lead to wide propagation and remote triggering. Such as triggering an avalanche from a low angled slope connected to a steeper slope. 

    A very large, and remotly triggered avalanche on 2/4. ENE Aspect, NTL.

  • Wind Slabs

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

    Upper elevations have seen continued wind-loading from SW to NW winds for several days. Avalanches on wind-loaded slopes could further step down into deeper weak layers, producing very large and deadly avalanches. Travel in or below wind-loaded terrain should be avoided. 

    A remotely triggered and wide propagating avalanche above treeline. This avalanche occurred in the NW Mountains before the last 2 loading events.

Avalanche Discussion

 

Around 10 to 18" of snow, (1 to 1.5 SWE) accumulated Wednesday Night. This was a significant and rapid loading event for our weak snowpack. A resulting natural avalanche event occurred during that same period. The majority of those natural avalanches occurred on near and below treeline slopes facing NE to SE. Give the observations tab a scroll and you can see what was documented yesterday. Several reports also came in yesterday, of some impressive remotely triggered avalanches in those same areas. 

From that same loading event, less natural avalanche activity was observed at above treeline elevations. The snowpack at those upper elevations is generally stronger and buried weak layers had not yet reached the tipping point. Drifting snow continued to load those slopes yesterday, and winds are forecasted to increase slightly today with more accumulating snow. With this continued loading, HIGH avalanche danger remains for upper elevations. The threat of large or even destructive natural avalanches is very real today. 

Régions couvertes