Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
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Danger d’avalanche

Thu
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A mostly stable snowpack has allowed people to step out into avalanche-prone terrain the past few days. If your decisions take you into this kind of terrain today, keep your eyes peeled for isolated areas of unstable snow. Steer around wind drifted features and select slopes free of rocky start zones and steep rollovers.

Problèmes avalancheux

  • Deep Persistent Slabs

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

    Weak snow near the ground failed in a handful of large avalanches initiated by a wet, warm storm on January 12. No recent avalanches, benign weather, and snowpit tests all show that this layer is gaining strength and is less likely to propagate. Although unlikely, it is not impossible to collapse one of these weak layers causing a large avalanche. If your decisions take you into steep, avalanche-prone terrain, hedge your bets on planar slopes with uniform snow coverage. Be wary of rocky, complex-looking start zones.

    (1/24/2022)

    Performing instability tests on weak layers near the ground in the Whitefish Range. 

    Photo: Cam Johnson

Avalanche Discussion

The most notable change to conditions is the 3 to 4 inches of new snow near Marias Pass in the Flathead Range. New snow and wind speeds averaging 10 to 20 mph with gusts as high as 30 mph likely formed fresh drifts that may be reactive to the weight of a rider. I would expect them to be small and harmless in size, yet could be consequential if you're caught above a cliff band or stand of trees. The rest of the Flathead Range and Glacier National Park, the Swan Range, and the Whitefish Range received optimal winds for transport, but little to no snow accumulation. Windward aspects were mostly stripped or contained faceted snow, which does a poor job at building slabs. If you see signs of freshly drifted snow, test it first on small terrain features before stepping out into more consequential terrain.

Although it is unlikely to trigger a deep persistent slab, give a second thought to very complex, rocky terrain where start zones can have thin snow coverage. It is in these areas where your weight can impact weak layers near the ground. Snowpit tests and recent observations all show that this weak layer is gaining strength and becoming more difficult to trigger. Ride one at a time and give yourself some space from rocky terrain features and convex rollovers.

Régions couvertes