Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The likelihood of small wet slides—both natural and human-triggered—will increase as the day warms up. Avoid traveling beneath steep, rocky slopes that are receiving direct sun. You could trigger avalanches up to 2 feet thick where the wind has drifted snow. 

Lawinenprobleme

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–1.5

    Sunshine and warming temperatures today will increase the likelihood of both natural and triggered wet slides. The 4-8" of snow that fell last week is sitting atop slick crusts—an excellent recipe for wet snow avalanches once you add direct sun. The steep and craggy nature of the Sawtooth Mtns makes them especially adept at producing numerous wet slides. You could trigger a wet avalanche on steep slopes that face the sun (S-E-W). Although likely to be small, these slides can travel quickly on the slick surfaces beneath them. Natural wet sluffs are likely to occur as the day heats up—so pay attention to the terrain that's above you.

  • Wind Slabs

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

    Yesterday, a heli ski guide triggered a wind slab while stomping cornices along a ridge in the Western Smokys. It broke about 100' wide and 12" thick and ran on a slick crust (photo above/right). On Horton Peak, Ben reported shooting cracks running 15' in fresh wind drifts. On Wednesday in the Smoky Mtns, Ethan found small wind slabs up to 1' thick (photo).

    You could find "garden variety" fresh wind drifts and slabs—those that have formed in the past few days and may be poorly bonded to underlying crusts or lower density snow. While less likely, there is also a chance of triggering a larger wind slab avalanche breaking into persistent weak layers (photo) that have formed during the past 2 months of dry weather. 

    Pay attention to how the snow feels under your board(s) or machine. If the snow surface suddenly stiffens or becomes more supportable, you've likely found wind-drifted snow. Surface texture such as ripples and dunes can be indicative as well. While you're not likely to trigger a large wind slab avalanche, it could be big enough to take you for a ride—so think about the consequences of any slope you ski or ride.

    (3/11/2022)

    A heli ski guide triggered this small wind slab on Friday while stomping cornices along a ridge. It broke 12" thick and 100' wide, running on a slick crust. Western Smokys, 9000', E aspect. Photo: Sun Valley Heli Ski

Avalanche Discussion

Conditions aren't scary out there, or particularly dangerous, but there are enough smaller problems that you need to keep your head on a swivel. If I had one word to describe the avalanche conditions, I wouldn't use LOW or MODERATE...I'd use "annoying". 

Normally, wind slabs and wet slides are two of the more predictable avalanche problems we deal with. The elephants in the room are persistent weak layers that we've formed during the past two months of dry weather—facets, crusts + facets, and surface hoar. We've seen a few avalanches where wind slabs have broken thicker and wider than expected (example) when they fail on these weak layers. In the Banner Summit zone, the wet storm at the very end of February triggered a cycle of persistent slab avalanches breaking on facets, crusts, and surface hoar. 

The prolonged dry spell produced several weak layers, but the wind, sun, and warm temps also produced a high degree of variability. Persistent weak layers + variability leads = unpredictability. When conditions are more unpredictable, it leads to a degree of uncertainty that makes forecasters unhappy. We don't like rolling the dice. Despite the MODERATE danger and relatively low likelihood of triggering a large avalanche, many avalanche professionals remain wary of some slopes. Those of us at the avalanche center are tending to avoid steep slopes at upper elevations that are shaded (more likely to harbor weak layers) and wind loaded (adding more load to the weak layers).  

Catch up on what happened this past week in Ethan's latest Weekend Update.

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