Boletín de aludes

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Peligro de aludes

Tue
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’re most likely to encounter unstable snow on slopes with wind-drifted snow. This new snow is adding additional stress to the weak snow buried deeper in the snowpack. Even on slopes sheltered from the wind, these weak layers create conditions that make human-triggered avalanches a possibility today. Be aware of this possibility and plan accordingly as you travel in the mountains today.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    On Thursday a snowboarder remotely triggered an avalanche in Croy Canyon, and on Friday snowmobilers triggered a slide near Couch Summit in the Soldiers. In both of these cases, the snowpack consisted of recent or past wind transported snow atop a weak, faceted snowpack. In the portions of this zone with a deeper snowpack, the same layer of surface hoar that has produced much of the reported avalanche activity this season also exists.

    Persistent weak layers are difficult to deal with. They can produce avalanches many weeks after they are buried and they provide fewer and fewer obvious signs of instability as the days without a significant loading event pass. They can break wider than you might expect and may be triggered remotely, from gentle terrain adjacent to steeper slopes. 

    Additional Discussion

    Winds have played a significant role in the slab formation portion of the avalanche equation in the past week. As time passes without significant amounts of new snow, these aging drifts are bonding to the surfaces that they were deposited on. However, the possibility of triggering one of the slabs remains, particularly in heavily loaded upper elevation terrain. These slabs are also adding stress to the weak snow described above.

    While most of this zone didn't see significant precipitation, several inches of snow fell in the Soldier mountains last night. Winds have already picked up and moved this new snow into drifts that may be sensitive to the weight of a rider or skier today.

Avalanche Discussion

This year, we’ve spent a lot of time talking about the surface hoar that was buried in early December. There is a good reason for that — this layer has produced dozens of human-triggered and natural avalanches. However, the complexity of the snowpack is increasing as the season progresses.

In addition to adding new snow, each storm buries a new interface to think about. Depending on the character of the older snow, the bond at this interface can vary significantly in strength. As the complexity of the snowpack increases, it becomes more and more difficult to confidently assess the stability of a given slope. 

Yesterday, in the southern portion of the Sawtooths, I found that a subtle crust accompanied by a thin layer of weak, sugary snow (facets) produced unstable snowpack test scores. This layer was buried by the storm that began on New Year’s Eve. Another week, another weak layer. 

You can try to limit some of the uncertainty present when dealing with complex avalanche problems by keeping track of these layers in the areas that you frequent. However, it's very important to recognize when you are dealing with a problem that is more complex than you can safely deal with. Unfortunately, this seems to be where we are headed this year. In this scenario, your best bet is to step back a bit and pad your uncertainty by building healthy margins for error into your travel practices.

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