Boletín de aludes

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
Ver en el mapa

Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
Open full map
Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Watch for and avoid steep slopes with stiff, wind-drifted snow. You're most likely to find wind slabs in alpine and upper elevation terrain. Triggering a large avalanche on weak snow deep in the snowpack remains a possibility on very steep, rocky, wind-affected slopes. Large avalanches in terrain sheltered from the effects of the wind are unlikely. 

 

Problemas de aludes

  • Persistent Slabs

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

    Weak snow near the ground forms the base of the snowpack in many places in this zone. This remnant snow from October exists on shaded slopes (NW-N-NE-E) at middle elevations and most slopes at upper elevations. Although we are two weeks out from a significant loading event in this zone, many experienced backcountry travelers and local professionals continue to give slopes with this snow at the base of the snowpack a wide berth. Even though I love playing in the steep terrain that exists in much of this zone, I'm happy to count myself amongst that group.

    If I were to go out looking for this problem today, this is the type of terrain I'd head for:

    • Steep: slopes about 35 degrees and steeper
    • Rocky: slopes with variable snow cover due to the roughness of the terrain
    • Wind-affected: slopes where strong winds produced variable snow cover due to scouring and loading

    Dealing with problems like this is just plain hard. Not to mention frustrating. We don't have a lot of experience with these types of problems in other aspects of our life. If you go into terrain that looks like what I just described it isn't likely that you are going to trigger a large avalanche. But it is a very real possibility. The choice of what type of terrain you enter on any given day is up to you, but it is important that you are honest with yourself about the types of risks you are taking by doing so. For me personally, I'll be continuing to avoid the terrain where this problem exists.

Avalanche Discussion

FRESH WIND SLABS

This zone received less snow (3-5") late last week than the mountains to the north and west. There, multiple groups triggered wind slabs resting on weak snow surfaces.

On Saturday I intentionally triggered a 6-18" thick wind slab that broke about 100' wide on a SE-facing slope at upper elevation in the Sawtooths. That same day, a group triggered two wind slabs near Copper Mountain on steep, upper elevation, northerly aspects. The slides were 6-18" thick and broke 40-100' wide. They released near exposed ridgelines, and both slides broke wider than your "run of the mill" wind slab due to a weak layer of facets buried directly beneath the fresh wind-transported snow. 

If I headed out skiing or riding in this area today I'd still have my guard up. Here are a few reasons why:

  • These slabs are sitting on a few different weak snow surfaces such as facets, crusts with facets, and surface hoar. These types of weak snow are slow to heal and can cause avalanches days to weeks after they have been buried.
  • Continued wind loading this weekend, and another inch or two of snow overnight (accompanied by more wind) will form fresh drifts and help these older drifts to stay reactive to the weight of a skier or rider. 
  • Slabs that fail on these types of weak layers (called persistent weak layers) can do so in ways that surprise you. They may break wider than you expect and further above you than you might expect.

Your best bet for avoiding having a problem with these slabs today is to spend some time looking at the snow with an eye out for textures that indicate the wind has been at work (ripples on the surface of the snow, large pillowy dunes of snow, etc.). Pay attention to how the snow feels under your skis or your machine. If you are seeing signs of loading or feeling the slab stiffening, alter your course to somewhere with softer snow at the surface. You'll find better skiing and riding and much safer conditions, a real win-win.

Regiones cubiertas