Bulletin d’avalanche

Southeast Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Dangerous avalanche conditions exist for areas that have received 10 inches or more of new snow which will be commonly found in the Northwest Mountains.  Additional snowfall today will increase the number of locations with enough new snow to cause a problem.  Anticipate avalanches to break at or just below the old snow surface.  You should expect an increase in avalanche size on leeward terrain features where west-northwest winds deposit snow.  Keep a close eye on snow totals in the terrain you are traveling to help clue you into the increased hazard for areas with 10 inches or more of new snow and leeward terrain features.

Problèmes avalancheux

  • Storm Slabs

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

    Small avalanches breaking in the new and recent snow will become more common as snow totals increase during the day.  Slabs will be most sensitive to human triggers in wind-loaded terrain or on shaded aspects.  Watch for cracking in the snow and use small test slopes to help identify the problem.  Be cautious above terrain traps where a small avalanche can push you into trees, rocks, or gullies.  This avalanche problem poses the greatest threat on drifted terrain features as avalanches will be larger.

    Shooting cracks, like this, are signs of unstable storm slabs.

  • Persistent Slabs

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

    Hard slabs that break 2 to 6 feet deep on weak layers near the ground remain a low likelihood concern.  The problem has become increasingly stubborn and isolated, and it has been several weeks since we have observed a persistent slab avalanche.  There is lingering uncertainty that skiers or riders can trigger a large avalanche from the margins of the slab where it thins out,  especially at higher elevations on northerly and easterly aspects.   Cornice falls can also trigger large avalanches.  You can reduce your risk by traveling where the snowpack is deeper and more uniform.  Regroup in safe zones that are clear of unusually wide and long-running avalanches.  

    An example of a thick, hard persistent slab that released naturally in mid-February.

Avalanche Discussion

The current storm has brought wide-ranging snowfall totals across the area with a 2 to 12-inch spread as of 4 AM.  Areas in the northwest mountains have done the best with snowfall continuing overnight from the northwest flow with totals pushing a foot so far with an additional 4 to 7 inches forecasted for today.  Areas in the Southeast mountains received less snowfall overnight and are generally in the 2 to 7-inch range with only a couple more inches expected today.  The avalanche hazard today will be dictated by storm totals.  Areas with larger storm totals will have a greater hazard, so keep a sharp eye on storm totals throughout the day as more snow stacks up.

In the Northwest Mountains, expect to find a foot or more of new snow with loading continuing throughout the day.  The potential avalanche size will steadily increase as more snow stacks up. On the north half of the compass, not far below the old snow surface, is a layer of weak Near Surface Facets, that will make human-triggered avalanches likely (Check out these two observations 1,2 for details or watch this video).  On the south half of the compass, the storm snow is commonly falling on slick melt/freeze crusts.  If the snowfall forecast for today verifies expect the avalanche hazard to increase throughout the day.  Both drifted features and sheltered terrain will present dangerous avalanche conditions.  Heed warning signs like cracking or collapsing as clear signs of instability.  Expect human-triggered avalanches and the possibility of some natural avalanches as well.  Your best line of defense in the Northwest Mountains will be choosing low-angled slopes and avoiding wind-drifted features.

In the Southeast Mountains, snow totals are a bit more subdued with wind-drifted terrain as the most concerning.  If you observe about 10 inches or more of new snow, expect that the danger rating has increased to CONSIDERABLE below treeline.  The greatest hazard will be on leeward terrain features where the wind has deposited snow and increased slab thickness.  Sheltered areas may produce thin, shallow slabs that are small in size, but remember that being pushed into a terrain trap like rocks, trees, or gullies can have serious consequences.  There is the potential for areas at the heads of Cement and Brush Creeks to pick up more snow than areas near Crested Butte, so if your travels plans put you in those areas be prepared for increased storm totals and increased avalanche hazard. 

Régions couvertes