Boletín de aludes

Banner Summit

Sawtooth Avalanche Center
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Peligro de aludes

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

Lo esencial

Triggering a large avalanche is unlikely. Continue to use extra caution on very steep, rocky, wind-affected slopes. Small but sensitive wind drifts formed during yesterday's storm and overnight. Be on the lookout for these along upper elevation ridgelines and be alert to the consequences of being caught in even a small slide in the terrain you are traveling in.

Problemas de aludes

  • Persistent Slabs

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

    Based on field observations and the pattern of avalanche activity, the weak layers in the snowpack have become dormant in this zone. Warm temperatures and dry conditions last week finally gave these weak layers some time to rest. They haven't disappeared, but triggering a slab on these weak layers is unlikely.  Snowfall yesterday has not significantly changed this equation.

    Even though triggering a persistent slab avalanche is unlikely, that's different from impossible. These weak layers exist on nearly all slopes and if you commit to entering avalanche terrain you should know that they are under your feet or sled. There's still a small chance of triggering a persistent slab avalanche on very steep (approaching 40 degrees), rocky, wind-affected slopes. Terrain like this is most common at upper elevations. Because these weak layers are deeply buried, any slide that fails on them will be large and destructive.

    ADDITIONAL DISCUSSION: Wind slabs formed during yesterday's storm and overnight. This zone is generally spared from the wind and I expect these slabs to be relatively small and isolated. You are most likely to find these slabs near exposed, upper elevation terrain, like ridgelines and in gullies. Though small, these slabs will be sensitive to your weight today. Be alert to the consequences of being caught in even a small slide in the terrain you are traveling in. 

    (3/5/2021) Persistent weak layers in the Banner Summit zone are unlikely to produce avalanches - but they're still there. Here, a layer of surface hoar 3' down didn't fail during a snowpack test, but sheared when the block was pried out of the column. N, 8400'.

Avalanche Discussion

AVALANCHE DANGER

The avalanche danger scale is an imperfect tool. There, I said it. But the shortcomings of the scale aren't necessarily a problem related to the danger scale itself, they are natural outgrowths of the problem at hand. When we rate the avalanche danger for a given zone we are trying to describe the wide range of snow and avalanche conditions you will encounter over a roughly 800 square mile area, using just a single word. When you think about it this way it should come as no surprise that the danger scale has its shortcomings.

As avalanche forecasters, we use the avalanche danger scale because it is a way to quickly convey information about the backcountry snowpack to our users. But, it isn't the only tool we use. The avalanche problems give you an idea what type of issue you should be thinking about, and the graphics next to the problem help you understand where the problem is most likely. Personally, I spend the great majority of my forecasting time writing text that is intended to help you understand what you might find out there. So, while the danger scale is a good starting point, it shouldn't be your end point. 

One thing that isn't communicated well with the danger scale is the element of uncertainty or unpredictability that exists in an area. This can be a very important piece of information for a person traveling in the backcountry. As we see danger dropping to LOW in almost our entire area it is easy to find yourself thinking that conditions are the same everywhere. But, this isn't the case. There are places in our forecast area where I just can't convince myself are a good idea to go right now. This isn't because I think triggering an avalanche is much more likely there, its because there is a level of unpredictability that I'm just not comfortable with. The thought of entering big, open bowls peppered with rocks in the alpine terrain of the Boulder, White Cloud, and Pioneer Mountains makes the hair on the back of my neck stand up.

What is it about this terrain that is so concerning? Thanks to a combination of wind and a lack of snowfall, the snowpack in these areas has stayed relatively thin all season long. A dense, stiff slab is sitting on top of the weak snow that has plagued us all season, and thin areas in the snowpack allow a skier or rider better access to this weak snow. These aren't the only places this combination exists, but they are the first that come to mind. If you find yourself looking down past your ski tips at this type of terrain today I challenge you to prove to yourself why entering that terrain is a good idea. If you feel comfortable with your knowledge of how the snowpack will behave, by all means, have at it. The early season snow in our area has behaved unpredictably all season long, creating large avalanches with small loads and producing slides many days after loading. For me, this unpredictably has me playing on the conservative side of things in areas with this sort of snowpack. 

 

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