Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

Thu
Alpin
3 · Marqué
Limite forestière
2 · Modéré
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

Large avalanches, 1-4 feet thick, are most likely to be triggered in areas where wind has formed drifts or stiffened the snow surface. In areas sheltered from the wind, avalanches are less likely, but they’re still possible. You could trigger avalanches remotely—from flat terrain below, above, and to the sides of steep slopes.

Problèmes avalancheux

  • Persistent Slabs

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

    What and where is it: You could trigger 1.5-4 foot thick slabs, especially where wind formed drifts or stiffened the snow surface. Triggering an avalanche is less likely—but not out of the question—on steep slopes that are completely sheltered from the wind. The slabs rest above a variety of weak layers (facets, surface hoar, crusts, and combinations). The widespread nature of these weak layers means avalanches are possible on many aspects. 

    How can you recognize it: Snowpack cracking, and collapsing or whumpfing, are clear signs of unstable conditions. Watch for snow pillows, dunes, and ripples, and feel for stiff snow under your feet or sled. These are signs the wind has been at work transporting snow. Persistent Slabs won't always present with obvious signs of instability, assume the weak layers exist on most slopes. 

    How can you manage it: By avoiding steep, wind-loaded slopes, you can significantly reduce your chances of triggering an avalanche. Persistent Slabs can release in surprising ways, break wider than expected, and release above or hundreds of feet away from where they are triggered. Remotely triggering an avalanche from flat terrain near steep slopes is a real possibility. Keep a close eye on your partner and the terrain that's above you. Manage your group by riding or crossing steep slopes one at a time, and avoid areas where terrain features like gullies, cliffs, or dense trees could increase the consequences of even a small slide.Additional Discussion: You may be able to trigger wind slab avalanches that have formed near ridgelines and in cross-loaded areas on the sides of gullies. The size and chance of triggering these slides increase significantly as you climb into windier, alpine terrain at upper elevations. These avalanches could step down to the buried weak layers described above.

    (12/30/2024)

    Skiers observed this natural avalanche near the Baker Ck. summer trailhead. Avalanches like this one are possible in the Banner Summit zone in both sheltered or wind affected terrain. 

     

    Photo: Jon Preuss

Avalanche Discussion

In the Banner Summit zone, weak layers are buried deeply in many areas, making avalanches more difficult to trigger. While there have been fewer reports of persistent slab avalanches here, that shouldn't be interpreted as a sign of stability. As we move further away from the post-Christmas loading event, the snowpack has started to adjust to the load. However, we're still cautious about entering or travelling below avalanche terrain due to widespread signs of instability over the past week. 

These are just a few key observations. For more, visit the Observations Page.

Continued snowfall and wind today will keep conditions on edge. You may encounter fresh, soft, and thin wind slabs near ridge tops, steep cliff faces, and chutes. While these slides are unlikely to be large enough to bury people, they could still carry you into dangerous terrain or trigger larger, more hazardous, Persistent Slab avalanches. To minimize risk, ski or ride slopes one at a time and seek out non-wind-loaded areas. Opting for non-avalanche terrain is a smart way to manage today’s avalanche risks and stay safe. You could trigger an avalanche remotely, keep a close eye on your partner, and the terrain that's above you.

Régions couvertes