Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
Voir sur la carte

Danger d’avalanche

Thu
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 5 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

New and wind-driven snow have formed sensitive slabs large enough to bury and injure a rider. A small avalanche could trigger a much larger, more dangerous avalanche on a weak layer buried deep in the snowpack. Reduce your exposure to steep terrain as you climb higher.

Problèmes avalancheux

  • Wind Slabs

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

    Vicious southwest winds have drifted recent snow into hard slabs that may be sensitive to a rider's weight. Expect slabs to grow thicker and more dangerous as you climb into the upper-elevation band. Reduce your slope angles and exposure to steep, leeward-facing terrain if you are riding in an area that received more than about 6 to 8 inches of new snow.  

    Utilize small and inconsequential test slopes to test the sensitivity of new snow. If you see cracking around your boards or machine, then you’ve found a slab avalanche problem. Dune-shaped drifts or textured surfaces will be visual giveaways to where this problem exists. Stick to terrain sheltered from the wind. A triggered slab or cornice fall is the most likely trigger for a very large and destructive avalanche on a buried persistent weak layer.

    A photo from early January of active wind loading along a ridgeline. Expect similar conditions today. Ride around areas where you see this and head for terrain sheltered from the wind. 

  • Wet Slabs

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

    Weak layers buried deep in the snowpack are untrustworthy. Yesterday's precipitation typically wouldn’t set off any alarm bells with most buried weak layers, but this one - the January Drought Layer - seems to produce massive avalanches with every kind of weather event.

    The most likely cause of an avalanche failing deep in the snowpack is a triggered avalanche in the new snow or a falling cornice. A rider hitting a thin part on the slope would be another likely candidate. On aspects that face northwest to east to southeast, your safest bet is choosing lower-angle slopes . Weak layers are less common on west and south aspects.

    (3/22/2026)

    Crown from a second slab avalanche that was likely triggered by debris from a very large (D3) avalanche on the north face of Sixmile Mountain in the Swan Range. 

    Photo: Flathead Avalanche Center

Avalanche Discussion

If you go powder chasing at upper elevations today, be ready to get pounded by some wind. I’d be hunting for terrain sheltered from southerly and westerly winds. Your best bet for good, safe riding will be on lower-angled slopes well off prominent ridgelines. Looking for sheltered, treed terrain above about 6000 feet should give you the goods. 

While hunting for good riding, be sure to keep new snow and old snow avalanche problems at the front of your mind. Assess storm snow totals as you move from basin to basin or climb in elevation. Adjust your terrain selection based on wind loading and new snow totals. Be very wary of steep, upper-elevation start zones that are being loaded with wind-drifted snow. There is a high degree of uncertainty about what would trigger an avalanche failing deep in the snowpack. Recent avalanches on this weak layer are propagating up to 2000 feet wide and failing up to 8 feet deep. A small avalanche, or possibly wind loading alone, may set off more.

Régions couvertes