Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
Voir sur la carte

Danger d’avalanche

Tue
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Watch for and steer around small, isolated pockets of wind-drifted snow on the leeward side of ridges and gullies. These may be consequential if you get caught above cliff bands, stands of trees, or gullies. If your choices take you into steep terrain, select slopes with clean runouts and only expose one person at a time.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Southerly winds increased overnight to speeds capable of transporting snow. If you find slabs of drifted snow, they will likely be reactive to the weight of a rider and small in size. Identifying a pattern today may be tricky since most southerly and westerly fetches are capped with a sun or rime crust, thus reducing the snow available for transport. I am more skeptical of areas further down the slope where winds may vary in direction due to localized channeling. Identifying surface textures is your key today. Steer around pillowy-looking drifts or dune-shaped features.

    (1/3/2023)

    Active blowing snow and drifted features, like this one, are your two primary tools for avoiding getting caught in an avalanche today. 

    Photo: Ted Steiner

  • Persistent Slabs

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

    Since the widespread avalanche cycle on December 26th-28th,  only two of 81 observations throughout the forecast area noted signs of instability. Both reports are of loud audible collapses felt on varying aspects at the middle and upper elevation bands, while the rest of the observations mostly describe a stable snowpack. This is evidence the problem still exists but is mostly unreactive. The consequences of a triggered slide failing near the ground have us wary of removing the problem right now. If you decide to ride in avalanche terrain, manage this unlikely problem by choosing slopes with smooth, fanned runouts free of surface obstacles.

    (1/7/2023)

    A very large avalanche which failed during the rain event sometime between December 26 to December 28. 

    Photo: Kevin Oberholser

Avalanche Discussion

Wind speeds overnight clocked averages of roughly 30 mph at both Mt. Aeneas in the Swan Range and Hornett in the Whitefish Range. Snowslip in the Flathead Range/Glacier National Park region averaged 16 mph with gusts to 47 mph. Wind directions were out of the south and southwest. Today winds will remain at speeds capable of transporting snow. The question is, where is there snow available to transport?

South and west-facing aspects would generally be ripe and loaded with fuel for the wind slab machine but are currently capped by a sun or rime crust. This will drastically limit snow available for transport. However, strong wind speeds can hug terrain features and channel through valley floors, drifting snow in unusual ways. This is where I’ll have my eye today. Look for isolated pockets of drifted snow on cross-loaded terrain features, like gullies and ribs. A textured surface or blowing snow will be your visual clue for areas to steer around. Cracking beneath your feet or machine is a sign you found the problem, and it is too late if it is in steep terrain. I suspect any wind slab to be relatively harmless in size. The primary concern would be getting caught in consequential terrain.

Recognizing the consequences of your terrain choices is vital regardless of whether it is Low Danger. More options exist for riding in steep terrain, but it does not mean getting caught in an avalanche is impossible. Recognizing the consequences of what is below you is good practice before committing to steep terrain. Ask yourself, “what if I am unlucky and this does slide?” and “what will I get dragged into or go over?” Terrain traps compound the consequences of a small or large slide. You can offer yourself a margin for error if the unforeseen happens in terrain with long, smooth runouts. Positioning a partner capable of performing an efficient rescue in a safe location adds another margin if things go wrong.

Régions couvertes