Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 7 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Weeks of dry weather and recent wind erosion have reduced the threat of avalanches on many slopes.  Lingering concerns are most likely found on recently drifted slopes where you might trigger a thin, hard slab like this skier-triggered slab yesterday, or in rare cases, there's potential to be surprised by a deeper and wider avalanche that is large in size.  The safest and highest quality riding is in wind-protected terrain at lower elevations or wind eroded terrain as you gain elevation.  

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1.5–2.5

    Although instabilities are becoming increasingly harder to find, the most hazardous concern is the lingering threat of triggering a large slab that fails 2 to 4 feet deep on depth hoar, facets, and faceted crusts without obvious warning signs.  In the Northwest Mountains, these slabs are most likely to be triggered in terrain where slabs are thinner or variable in depth from past wind events. The most reliable way to manage this problem is by choosing slope angles less than 30 degrees.  Southerly aspects, low elevations, and heavily wind-eroded terrain typically offer safer snowpacks, where slabs are less common.  

    A persistent slab avalanche that likely failed during the recent wind event (1/16 to 1/17)

    Photo: Crested Butte Avalanche Center

  • Wind Slabs

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

    Strong to extreme northerly winds last week formed thin, hard slabs on features that collected drifting snow. The wind event mixed down to mid and low elevations, cross-drifting relatively small slabs onto weak, faceted snow surfaces - most commonly on the shady side of the compass where there was more snow available for transport and on higher southerly aspects.  These slabs will stand out as smooth, hard, lens-shaped snow formations, next to wind-eroded areas or softer, wind-rippled snow surfaces.  Although they are typically stubborn to trigger now, skirt around these harder drifts in consequential terrain to avoid the threat of getting pushed into trees, rocks, or gullies.  

    A skier triggered wind slab on Tuesday.  Previous crossloading formed a thin, hard slab over facets.  (1/20/2026) Photo: Crested Butte Avalanche Center

Avalanche Discussion

Last week's wind events scoured into existing snowpacks to find transportable snow and redistributed some of it into pockets of thin hard slabs on various aspects around the compass and at all elevations.  The dominant wind direction during the culmination of extreme winds on Friday and Saturday was out of the northwest, and we've trimmed the wind slab rose to highlight the aspects that most commonly caught drifting over weak snow surfaces.  You can certainly find these drifts on other aspects as well.  It's easiest to simply read the snow surface and look for the obvious hard lenses of snow in concavities or other catchments that collected the drifts to identify the problem.  Yesterday's skier-triggered wind slab demonstrates that even though most drifts are difficult to trigger now, they remain a threat in consequential terrain, especially where they formed over facets on the colder aspects.  

Persistent slabs breaking in old December and November weak layers have become unlikely.  The combination of nearly two weeks of dry weather, along with more recent wind erosion events, has made the issue increasingly isolated and stubborn.  The thinner snowpack in the Southeast Mountains is more prone to losing slabs from both faceting and wind erosion, and we have higher confidence that the danger is lower there.  This video demonstrates the typical situation.  The threat of a persistent slab is also diminishing in the Northwest Mountains, though the large potential size for isolated instabilities is currently dictating our travel advice.  This persistent slab that ran around Saturday demonstrates the type of features that are most concerning: slopes on shadier aspects with poor structure that saw loading (rather than erosion) during the weekend wind extravaganza.  If you look at the zoomed-out photo of the terrain, you can see that most slopes in that basin have raised tracks and sastrugi, an indication of wind erosion. Yet a few features behind tree fences and in concavities caught drifting instead.  Be careful of those types of slopes on larger, steeper terrain.  

Upcoming Outreach Events:  

Fireside Chat:  Jan 23, Dave Scheefer "Historical avalanches in Gunnison County."  Mallardi Theatre 5-7 pm.

Trailhead Day: Jan 24, Slate River, 10 am-2 pm.

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