Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 7 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Triggering an avalanche on weak layers buried 3-5 feet deep is becoming less likely. Unfortunately, any slide that is triggered would be very large and take out most of the winter's snowpack. You can reduce most of the risk by sticking to lower slope angles and avoiding shallow areas in the snowpack.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2–3

    This zone has persistent weak layers buried 3 to more than 5 feet deep on most middle and upper elevation slopes. In the northern Sawtooths on Friday, I found these layers buried beneath a dense slab that was 4-5 feet thick (see snowpit). I didn't even bother to do a snowpack test because 1) they don't work well on layers this deep, and 2) the presence of these layers is the most important observation. Knowing these layers are buried deeply tells me that it's unlikely you would trigger a slide, but if you did, you probably wouldn't live to tell about it. That's what makes these "low probability, high consequence" situations so difficult.

    Today's forecasted 3-5 inches of new snow will not significantly impact these layers, and we remain in a holding pattern. With deeply buried weak layers, it's important to avoid thinner areas where you can more easily impact the weak layer. You can reduce your risk of triggering a monster by avoiding:

    • Wind-affected terrain: The wind can create thinner spots where the weak layer is closer to the surface. These are often connected to wind-loaded areas where there is more load on the weak layers.
    • Steep, rocky slopes: Rocky or "alpine-like" terrain typically has shallow areas where your weight can more easily affect buried weak layers.

Avalanche Discussion

There's nothing easy about making decisions when there are lingering concerns about buried persistent weak layers. To improve our approach to these situations, there is no way to avoid the concept of risk tolerance. Do you like to drive under the speed limit with your headlights on during the day, or do you tend to drive fast and take chances? 

The problem with applying risk tolerance to backcountry decision making is that we can rarely quantify the actual level of risk we are taking. This is especially true with lingering persistent slab problems. Instead, it can be more useful to evaluate your tolerance for uncertainty. When faced with an uncertain situation, we all respond in different ways, but many of us stick our heads in the sand and pretend there's no problem. That can be a very dangerous approach in avalanche terrain.

My recommendation is to embrace uncertainty and come up with a personal approach to manage it. Rather than getting hung up on assessing the risk ("maybe if we dig one more pit we'll have an answer") or pretending there's no risk, focus on the degree of uncertainty. With our current snowpack, trying to accurately quantify the level of risk is a largely fruitless pursuit. As we get further from significant loading events, it becomes harder and harder to assess the actual likelihood of triggering buried weak layers—especially when they're buried deeper than a few feet. So while I can't tell you exactly what the current risk is, I can tell you that the level of uncertainty is fairly high. Now we actually know something and have a valuable piece of data we can base our decisions on.

By definition, when the uncertainty is high, the level of risk could be low, high, or somewhere in between. It's better to assume the worst and make your decisions accordingly. For me personally, high uncertainty is the same as high risk. At times we may feel very confident (low uncertainty) that the risk is high—on those days, decisions are easy. When both our uncertainty is low and the risk is low—now those are the days we are waiting for. Those are the times to go big and feel good about it.

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