Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
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Danger d’avalanche

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

Points saillants

Dangerous and complex avalanche conditions have developed as new and wind-drifted snow falls on a weak snowpack. Avoid triggering a large and deadly avalanche by staying off of and out from under steep slopes.  

We have issued a SPECIAL AVALANCHE BULLETIN  through Sunday, February 2nd  due to challenging conditions and expected weekend traffic.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2.5

    Nearly a month of dry conditions has left the old snow surface remarkably weak. New and wind-drifted snow will not bond well to this surface and human-triggered avalanches are likely. These will not be your typical storm slabs as they might:

    • Break much wider than expected or well above you.
    • Wrap around terrain features into adjacent start zones.
    • Be remotely triggered from low-angle or flat terrain above, below, or beside steep slopes.
    • Travel quickly on crusty solar aspects, or entrain large amounts of faceted snow on shaded slopes.

    Slabs will be thicker and stiffer as you climb in elevation and on leeward slopes, where southwest winds have drifted storm snow. Stay off of and out from under steep slopes with 8 or more inches of new or wind-drifted snow.  Audible collapses are a clear sign of instability and a reminder to stick to low-angle terrain. 

    (12/28/2024)

    Natural or human-triggered slab avalanches may fail at the old snow surface, or slightly deeper on various weak layers.

Avalanche Discussion

This is the type of set-up where we often see a rash of human-triggered avalanches, near misses, or even fatalities: a weekend refresh on a weak structure following an extended period of low danger. 

So far, the storm totals are underwhelming as the bulk of precipitation is concentrated south of the advisory area.  However, last night's snow fell at relatively warm temperatures onto weak snow, so it is possible stations are under-reporting.  By the end of today, we will have received roughly 1.0 inches of SWE and 1 foot of new snow.  Regardless, the underlying weak structure has me skeptical of steep slopes on all aspects and elevations.  

Humans are creatures of habit. Over the last several weeks, our habits have included ranging freely through avalanche terrain. That is not a habit you'll want to carry into this weekend. Plan on dialing back your terrain and make a simple plan for the day. You can enjoy the fresh snow on low-angle slopes or slopes that have received less snowfall. 

Régions couvertes