Boletín de aludes

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Peligro de aludes

Fri
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 7 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You are most likely to trigger an avalanche in areas where wind has drifted recent snowfall. You may be able to trigger avalanches remotely—from gentle or flat terrain above, below, or to the sides of steep slopes. Cliffs, trees, and creek bottoms can increase the consequence of being caught in a slide. Picture where an avalanche would carry you before skiing or riding steeper slopes.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Today, you’re most likely to trigger a persistent slab avalanche on slopes where newly fallen and wind-drifted snow is stressing buried weak layers. Just a few hours of wind can turn the recent 5-10” of fluff into a stiff, 1-2’ thick slab.

    Our most prominent weak layer, a stripe of facets and surface hoar buried 1-2’ deep, can be found on most upper-elevation and shaded middle-elevation slopes. This layer was responsible for the slide triggered in the western Smokys on Sunday (pictured at right) and should be at the front of your mind as you choose slopes to ride today. 

    Dealing with persistent weak layers is tricky business. They may fail weeks after burial and slides may be triggered remotely—from above, below, and to the sides of steeper slopes. Persistent slabs can fail in surprising ways, break wider than expected, and span multiple terrain features that may otherwise contain storm slabs or wind slabs.

Avalanche Discussion

Before chatting more about our favorite weak layers, we should talk briefly about avalanche concerns involving snow from our recent Christmas Eve storm.

  • Yesterday, in the Soldier mountains I saw several small, loose snow avalanches that failed naturally during the storm and also after the storm as the sun warmed the rocks on very steep, sunny slopes. I expect this activity to continue today as the midday sun hits similar rocky terrain.
  • I also observed small, wind slab avalanches, and experienced cracking in freshly formed drifts along exposed ridgelines. Although it’s been eerily calm in the last few days, be on the lookout for these small, sensitive wind slabs at upper elevations. 

Concerning Persistent Slabs:There’s a tendency for people to get complacent when dealing with a long-duration persistent slab problem like the one presented by our buried surface hoar layer. This is especially the case as the obvious signs of instability (avalanches, cracking, collapsing) are on the decline. To combat this complacency, Scott suggested focusing more on the consequences of being caught in an avalanche on a given slope. I like this technique because it takes a layer that seems like old news, and forces you to consider it today, in real-time, and in the context of the terrain you plan to ride.

I’d like to add another tactic to your mental toolbox. The likelihood of triggering a persistent slab ebbs and flows with periods of additional loading and dry weather. So rather than thinking of the weak layer as one, long, drawn-out event, I compartmentalize it into separate loading events. In a sense, I treat it as a new weak layer with each storm. Now the tracks, and snowpack tests and avalanches from the previous loading event take up much less space in my mind.

With each storm, however small, try hitting the “refresh” button on your mental snowpack model. Clear out some of the clutter and biases of the last loading event and make room for the new information of a fresh snowpack to consider. Approach each day following our Christmas Eve storm with an assessment mindset. Ask yourself, “how will this new snowpack behave?”

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