Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

An atmospheric river will deliver rain as high as most ridgelines on Sunday, initiating a natural avalanche cycle. This will not be a good day to be out in the mountains. Avoid all terrain where avalanches can start, run, or stop until this storm is over.

Problèmes avalancheux

  • Wet Slabs

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

    Expect natural avalanches to occur on slopes over 35 degrees as rain destabilizes the recent storm snow. You may initially notice loose avalanches, but eventually, more dangerous slab avalanches will fail due to a weak snowpack structure. These slides could travel long distances on open slopes and entrain much of this season’s snowpack. On smooth rock ledges or grassy slopes, the entire snowpack could fail. Traveling in avalanche terrain is not recommended. 

    (12/2/2023)

    Large natural avalanches occurred on the Throne at Crystal Mountain—the larger of which connected terrain features and spanned far distances. Expect similar-sized avalanches on Sunday.  [SS-N-R3-D2-U]

    Photo: Crystal Mountain Pro Patrol

Avalanche Discussion

Since Friday, the volcanoes have received over 3 feet of snow, while areas closer to the crest have accumulated 1.5-2 feet. On Saturday, backcountry travelers in the Crystal Mountain and White Pass areas reported small natural avalanches, whumpfing collapses, and poor snowpack test results. Crystal Mountain Pro Patrol reported a widely breaking natural avalanche in unmitigated terrain that connected terrain features.

This bullseye information helps support observations of a poor snowpack structure. The storm snow sits predominately on a melt-freeze crust at middle to upper elevations, while it rests on bare ground at lower elevations. This distinction may be important on Sunday. 

We expect larger and more dangerous avalanches in areas where snow existed prior to this storm. This 11/30 interface was the point of failure for multiple avalanches around the region on Saturday, and we anticipate it will continue to be active on Sunday. Avalanches could break even deeper or gouge into older snow layers in isolated areas.

At the lowest elevations, you may find that avalanches are smaller. Any avalanche could be consequential at this time of year due to early-season hazards such as exposed rocks, open creeks, holes, or bushes. 

Régions couvertes