Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

It is possible to trigger an avalanche where the wind has formed fresh drifts of snow.  Look for signs of wind along ridgelines, saddles, and gullies. Move to less steep, or more sheltered terrain if you find rippled surfaces, dune-shaped features, or cracking around your feet or machine. Recognize that a surface slide could step down to buried weak layers, resulting in a larger avalanche. 

 

Problèmes avalancheux

  • Wind Slabs

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

    Yesterday's (Thursday's) snowfall and wind underproduced, limiting the size and distribution of fresh wind slabs.  Southwest winds increased overnight and remain near threshold speeds for drifting snow today.  Wind slabs may be resting on variable surfaces, including a weak facet/crust combination near the top of the snowpack. 

    Managing this problem can be straightforward:

    • Avoid steep slopes where you see blowing snow, scalloped surfaces, or dune-shaped features.
    • Shooting cracks around your boards or machine indicates that drifts are reactive. This should steer you towards lower-angled slopes or wind-sheltered terrain. 

    (12/20/2024)

    A small wind slab is visible just beneath a cornice near the summit of Elk Mountain. This slide likely failed during the intense wind event of 12/17-18. 

    Photo: Mark Dundas

  • Persistent Slabs

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

    Whumpfing collapses have been reported within the last three days. The most recent report of a large avalanche failing on weak layers is estimated to have occurred 5 days ago in the Flathead Range and was likely triggered by cornice fall (see attached photo).

    Weak layers formed in early December are now buried 2 to 3+ feet deep. An avalanche failing on this layer would be large and difficult to escape. Avalanche activity on this buried weak layer has been mostly limited to north and east-facing slopes.  A few isolated events have occurred on south-facing slopes. 

    The most straightforward way to avoid triggering a large and destructive avalanche is by sticking to lower-angled slopes where weak layers are present. 

    (12/24/2024)

    Recent natural avalanches on the lee side of the Flathead range show the lingering hazard of triggering large avalanches that break deep in the snowpack 

    Photo: Michael Reavis

Avalanche Discussion

Thursday's snowfall did little to increase avalanche danger except in particularly windy areas. Today should be a reprieve before the weekend storm. Recall, however, that variability has been the name of the game recently, so tune into subtle differences in the amount of recent snow, wind effects, and snowpack structure.

One notable nuance is a crust/facet combination that has been reported in the top 12 inches of the snowpack.  In some areas it has been sensitive in snowpack tests but lacked a cohesive slab above it. In wind-favored locations it may now have a slab on top of it. We will continue to load this weak structure (and our more deeply buried weak layers) as the weekend storm cycle progresses. 

Downloaded the app yet?

You can now access our region's forecasts, observations, and weather data directly from the Avy App (IOS; Android). Many features are accessible offline, so you can doublecheck danger ratings and travel advice on the drive to the trailhead or in the backcountry. 

Events and Education:

Want to start your New Year on the right foot? Sign up for a Partner Rescue Clinic for motorized Riders on January 4. Check out our calendar for other upcoming events. 

Régions couvertes