Bulletin d’avalanche

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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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 are most likely to trigger a large avalanche on shadier middle and upper elevation slopes where the wind has stiffened the snow near the surface. Slides can be triggered 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
    Unlikely
    Taille
    1–2

    This problem is most concerning where wind-stiffened slabs formed atop weak snow surfaces (facets, crust + facet combos, and isolated surface hoar) that developed during a month-long drought. These weak layers are ugliest on shadier NW-N-NE-E aspects at middle and upper elevations.

    Yesterday's remotely triggered avalanche in the White Cloud Mountains is a reminder that persistent slab avalanche problems are slow to heal. Snowpack cracking, collapsing, or whumpfing are clear signs of unstable conditions. However, a lack of these obvious warning signs doesn't mean you're in the clear.

    Persistent Slabs can release in surprising ways, break wider than expected, and be triggered from a distance. Your best way to play it safe today is by avoiding steep slopes facing the shady side of the compass where you suspect or feel that a slab has formed.

    Additional Discussion - Wind Slab: Be on the lookout for large dunes or drifts in upper elevation terrain. Given the variety of pre-existing slick surfaces and faceted snow, some of these recently formed wind slabs may remain sensitive to your weight. Although likely to be small, these slides can have outsized consequences in big terrain. 

    (2/10/2026)

    Slab avalanches on McDonald Pk in the southern Sawtooth Mountains. There are crowns under the cornices at the top of the photo, as well as under the cliffs. E and SE aspects 9,500-9,700'.

    Photo: Sawtooth Avalanche Center

Avalanche Discussion

Yesterday, Nick and I visited the White Clouds to gather information on the Persistent Slab problem. We targeted an area where we suspected we'd find both a slab and underlying weak snow. Finding the weak snow was easy. The recent month-long drought had significantly faceted the snow surface on steep, wind-sheltered slopes facing away from the sun. We knew these aspects were the most suspect, as evidenced by recent natural and human-triggered avalanches. 

Finding the slab was more difficult. The 6-8" of settled storm snow in our location was very low-density and seemed to lack the strength to propagate a fracture. The "slab" was thin and soft. Any very small collapses we observed extended no more than a ski pole's reach away. We anticipated finding a slightly stiffer slab and the "strong snow over weak snow" setup we were looking for as we continued to climb into more wind-exposed terrain. Although we observed evidence of recent wind loading on nearby slopes, the snow we traveled through remained soft. 

On the descent, we paused above a small, steep roll. Although to that point, we had not found the concerning "strong snow over weak snow" we were looking for, we opted to steer around the roll. After several turns down the slope, I swung wide left, inadvertently drifting beneath the steeper pocket I intended to avoid, triggering a collapse that traveled back up slope, releasing a small slab. 

The ability of this thin, soft slab to propagate as far as it did (~50') was surprising and demonstrated just how weak the underlying facets were on that particular slope. While I was not involved in the slide, it was unnerving and a reminder of how easily problems like these can catch us off guard. Although the slab is thin and weak in many areas, it wouldn't have taken much wind to turn this small slide into one with real consequences in large terrain. 

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