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

Human-triggered avalanches remain possible in areas of recently wind-hardened and drifted snow. Look for obvious signs of unstable snow, like cracks shooting from your boards or sled. Avalanches may be triggered remotely — from gentle terrain above, below, and to the sides of steeper slopes.

Problemas de aludes

  • Persistent Slabs

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

    You’re most likely to trigger a persistent slab avalanche where recently wind-drifted snow sits atop one of the buried persistent weak layers that plague the majority of the forecast area. These layers are most prevalent at upper elevations and on shadier middle elevation slopes. Wind-loaded slopes are more common in the Soldiers than in the mountains surrounding the Wood River Valley, so the chances of finding trouble are higher as you move west in this zone. 

    Although obvious signs of instability are becoming less common, this problem isn’t going away any time soon. When dealing with persistent weak layers there are a couple of things to keep in mind: 

    1. Triggering avalanches remotely — from above, below, and to the sides of slopes, is a real possibility. 
    2. 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. 

    Yesterday, the Sun Valley Ski Patrol intentionally released a sizeable slab avalanche on a north aspect while checking a closed area before opening the resort (see photo). The avalanche failed on weak, faceted snow near the base of the snowpack. While this slide is a “one-off” since the slab was deposited by snowmaking guns it foreshadows what may come when snow returns to the forecast.

Avalanche Discussion

The primary weak layers in our snowpack are easy to see, but obvious signs of instability are getting harder to come by. Triggering avalanches, cascading whumpfs and zippering shooting cracks can really drive home the message that the snowpack is unstable and dangerous. Even as these warning signs decrease, there are two primary weak layers warrant your respect and attention:

  1. We buried a widespread layer of surface hoar in early December. We’ve found these weak, feathery crystals from Banner Summit, down through the Sawtooths and western Smokys, across the valley into the White Clouds, south to Galena Pass, further south into the Boulders, and in the mountains east of Ketchum and Hailey. In short, we’ve found it almost everywhere we’ve been.
  2. In areas that harbor lingering snow from September and October, large, sugary depth hoar sits at the base of the snowpack. This layer is more common in the Sawtooths, Western Smokys, White Clouds, northern Boulders, and Banner Summit area.

Last night, we (the forecasters) had a meeting to discuss current conditions. We talked at length about the subtle differences in weak layers with changing aspect, elevation, and location. We also discussed the uncertainty of dealing with a widespread surface hoar problem – something that is rare in this area. Personally, I deal with complexity and uncertainty by dialing back the consequence of the terrain I choose to ride. Complex problems warrant simple terrain.

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