Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 6 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You're most likely to trigger a large avalanche on slopes where the wind has formed drifts or stiffened the snow surface. Avalanches are also possible on steep slopes that are mostly sheltered from the wind. You may be able to trigger slides remotely—from flat terrain below, above, and to the sides of steep slopes. Small wet avalanches are possible in very steep terrain facing the sun. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–2.5

    You're most likely to trigger a persistent slab avalanche on steep slopes that tilt away from the afternoon sun (NW-N-NE-E). It's these aspects that produced the most widespread natural and human-triggered avalanches over the last two weeks, and where our buried weak layers remain the most concerning. 

    Triggered avalanches may be 2-4' thick and release in surprising ways. They can be much wider than expected and be triggered remotely—from flat terrain below, above, and to the sides of steep slopes.  

    Snowpack cracking and collapsing are clear signs of unstable conditions. The best way to avoid trouble is to give avalanche terrain a wide berth. This includes gentler terrain below steep slopes. 

    (2/25/2026) A large natural avalanche on a NW aspect at 8800' on Copper Mountain.

    Photo: Sawtooth Avalanche Center

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2

    Over a foot of snow and strong wind built 1-3' thick drifts and slabs at upper elevations. Expect these drifts to be the largest and most sensitive on slopes facing N-NE-E and SE. 

    Look for them near or below ridgelines, along mid-slope ribs, and on aprons beneath chutes. Obvious, recent, cornice growth, dunes, or drifts are all signs that the wind has been at work. If you suddenly feel the snow surface getting stiffer, you've found a wind slab. 

    This problem is formidable on its own, but may also serve to trigger the larger and more dangerous persistent slab avalanches described above.

    (2/25/2026) A pair of large natural avalanches on a NE aspect at 8800' along the ridgeline between the two Copper Mountain summits. Clear evidence of wind loading and cornice growth is obvious in this photo as well.

    Photo: Sawtooth Avalanche Center

Avalanche Discussion

Yesterday's clearing skies allowed a first look at the natural avalanches that occurred from Tuesday into Wednesday. The pattern matches what we've seen since a return to snowier weather this February (plot). Snowfall and moderate to strong WSW-W and NW winds triggered natural avalanches on NW-N-NE-E and SE-facing terrain.

Some of these slides appeared to involve just the storm snow since Tuesday, and others broke into deeper weak layers. Most released in heavily wind loaded areas, but some broke mid-slope, or were triggered from above by smaller avalanches, indicating the sensitivity of the Persistent Slab problem even on slopes that are not obviously wind loaded.

We're coming off an impressive stretch of human-triggered slides, and by all accounts, this storm has increased our odds of triggering a large and dangerous avalanche. Today is a great day to approach the mountains with curiosity rather than an objective. Decide ahead of time which terrain you'll avoid, and stick to it. Reevaluate as you go, and don't let the beautiful day cloud your judgment. 

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