Bulletin d’avalanche

West Slopes South

Northwest 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 8 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

MORNING UPDATE: Increased upper elevation danger to CONSIDERABLE due to continued strong wind and greater overnight snow totals.

You could trigger an avalanche in steep, leeward terrain at mid and upper elevations. Strong winds Thursday night will rapidly redistribute low-density snowfall onto downwind slopes, ridges, and below cliff bands. Actively blowing snow and unusually deep, dense snow underfoot are key indicators to move to lower-angle terrain.

Problèmes avalancheux

  • Wind Slabs

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

    Fresh wind slabs will remain the primary avalanche hazard as strong winds and low-density snowfall impact the West South zone overnight Friday. These slabs will be most sensitive early Saturday morning, becoming less reactive as the day progresses. Wind speeds are expected to decrease Saturday, limiting additional wind loading during the day. In some areas, slabs may form on top of the December 24th crust, creating a potential sliding surface for any triggered avalanche.

    If you’re headed out early, anticipate large, fresh wind slabs at mid and upper elevations. Slabs will be largest at upper elevations, where more snow is available for transport. Wind slabs often present with a lens shape, with dense wind compacted snow at the surface. Look for these surface clues, and utilize small test slopes before approaching consequential steep terrain.

    (12/24/2025)

    Active wind-blown snow is a key indicator of fresh wind slab formation.

    Photo: Sam Clairmont

Avalanche Discussion

The West South zone has picked up minimal snowfall over the past 24 hours, primarily “dust on crust” conditions as a couple inches of new snow sit on the December 24th crust. Weather will become more active overnight Friday as temperatures drop, winds increase, and a few additional inches of snow accumulate at all elevations. The low-density snow will be quickly transported by wind, promoting fresh slab formation wherever the wind meets the snow, most notably at mid and upper elevations. The upper elevations of the volcanoes will likely stand out from the rest of the West South, presenting higher hazard, and potential for larger avalanches.

A thin layer of graupel has been identified within the snowpack near the Crystal Mountain area, along with the December 18th crust. Both layers have the potential to produce a larger avalanche in steep, rocky terrain. That said, reported avalanche activity associated with these layers has decreased over the past few days, suggesting they may be less of a concern now.

State and local resources are working diligently to reduce the impacts of destructive storms that occurred earlier this month. We can help by respecting affected communities, complying with road closures, and adhering to ski area uphill travel policies.

Régions couvertes