Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

You could trigger a 1-3 foot thick avalanche in areas where the wind has formed drifts or stiffened the snow surface. While it’s less likely to trigger avalanches in wind-sheltered areas, it’s still possible in steep slopes. To reduce your risk today, stick to smaller terrain and avoid areas with thick trees, gullies, or cliffs, as these features can increase the consequences of even a small slide.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2

    What and where is it: Near ridgelines over about, 8500, you could trigger soft or stiff, 1-3 foot thick slabs where wind formed drifts or stiffened the snow surface. While triggering an avalanche is less likely on sheltered, wind-protected slopes, it is still possible in steep terrain. The widespread nature of various weak layers (facets, crust-facet combinations, and possibly surface hoar) means avalanches are possible on many aspects. 

    How can you recognize it: Signs of instability include cracking, and collapsing or whumfing, are clear signs of unstable conditions. Look 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.  

    How can you manage it: To reduce your chances of triggering an avalanche, avoid steep, wind-loaded slopes. 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 below steep slopes remains possible.

    (12/21/2024) Skier-triggered avalanche near 9800' on a NE aspect in the northern Boulder Mtns.

Avalanche Discussion

Large persistent slab avalanches have become less likely, without the addition of heavy snowfall or strong winds. It is unlikely that the few inches of snow that fell over the last 24–48 hours will drastically increase the chances of triggering an avalanche. With a brief increase in winds this morning, you may find fresh, soft, thin wind slabs near ridgetops and below steep cliff faces and chutes. The slabs could overlie graupel or other weak snow at the old-new snow interface, making them easy to trigger. While these slides should not be large enough to bury people, they could carry you where you don’t want to go.

Across the forecast area, we've received reports of cracking, collapsing, and a generally poor snowpack structure:

  • Yesterday, in the Sawtooth mountains, Scott saw a large natural avalanche on the SE face of Decker Peak that likely happened last week, but it serves as a good reminder of the potential size associated with the persistent slab problem.
  • Sunday, a forecaster experienced several snowpack collapses—some in excess of 100 feet—in wind-loaded terrain in the Headwaters of the Salmon/Frenchman Creek area. 
  • Saturday, a group reported a human-triggered avalanche in wind-affected terrain near 9800 feet on a NE aspect in the northern Boulder Mtns (Galena Summit & Eastern Mtns zone).
  • Saturday, professionals in the Banner Summit zone (NE aspect near 8800' on Copper Mountain) reported a large collapse that sounded like a shotgun.

The mountains have been relatively quiet, with only a few natural avalanches and one human-triggered avalanche reported over the last week. However, with a poor snowpack structure and ongoing signs of instability—cracking and collapsing—we know that the weak layers are still weak and could produce large, consequential avalanches. Manage your terrain today by avoiding areas with obvious signs of wind loading. You can further reduce your risk by choosing simpler terrain with clean run-outs, free of any terrain traps, and only exposing one person at a time to potential hazards. 

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