Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

You're likely to trigger avalanches on slopes loaded by the wind. Small natural avalanches and cornice failures could trigger much larger avalanches as they cascade downslope. Slides can be triggered remotely—from flat terrain below, above, and to the sides of steep slopes.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    You're likely to trigger wind slab avalanches in steep, wind-loaded terrain. Intense loading rates may cause natural hard and soft slab avalanches and cornice failures. These slides can be large on their own but also provide an effective trigger for a much larger persistent slab avalanche, as described below. Wind speeds and snow amounts are greatest at upper elevations, but stiffer slabs may extend to lower elevations. Look for freshly forming cornices, dunes, or snow drifts; these are clues that the wind has been at work. Cracks shooting from your skis or sled mean you've found a sensitive slab. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Triggering a very large persistent slab avalanche remains a concern. You're most likely to trigger one of these slides in steep terrain facing WNW-N-NE-SE terrain (plot). These hefty 3-6' thick slabs rest above weak snow formed during January's drought, including surface hoar, facets, and facet + crust combinations.

    Recent observations indicate that this slab + weak layer combination is improving, but last night's/today's storm will put this process on hold.  Wind slab avalanches and cornice failures that run into middle elevations may provide effective triggers that break down to this deeper weak layer, causing a wide and destructive slide. Snowpack collapsing or whumpfing is a clear sign of unstable conditions. However, a lack of obvious warning signs doesn't mean you're in the clear. Persistent Slabs can release in surprising ways, break wider than expected, and release above or hundreds of feet away from where they are triggered. 

    (2/6/2025) Multiple avalanche crowns on Copper Mountain's E ridgeline.

    Photo: Sawtooth Avalanche Center

Avalanche Discussion

Last night's/today's storm will cause natural avalanches and build sensitive slabs near the surface. If winds ease, the afternoon sun may also cause sluffing in steep, rocky terrain. These new snow avalanches will be the most obvious problems to look for and avoid, but we can't forget the baseline persistent slab problem on which this action unfolds. We're only 48-hrs out from a major loading event that built 2-6' thick slabs atop weak snow that formed over a nearly month-long drought. Brief windows of visibility revealed a widespread avalanche cycle (more here). Since then, obvious signs of instability have been a mixed bag. In areas with thicker slabs (~3' or more), instability is less obvious, while thinner slabs (<3' thick) are collapsing more often. Despite the apparent positive trend in stability, there's a lot of uncertainty. For now, this problem and the severe consequence of being wrong are enough to keep us out of large avalanche terrain.

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