Boletín de aludes

Banner Summit

Sawtooth Avalanche Center
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Peligro de aludes

Mon
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

While not likely, you can trigger avalanches involving very dense, 2-4+ foot thick slabs on a variety of slopes today. The first sign of instability may be the large avalanche you trigger. These slides can be triggered a distance away from the slope that avalanches. Choose simple terrain free of terrain traps to reduce your risk. Small slabs of wind-drifted snow may be reactive to your weight in upper elevation terrain today.

Problemas de aludes

  • Persistent Slabs

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

    Layers of weak snow are buried beneath very dense, 2-4+ foot thick slabs. Triggering an avalanche on these layers is not likely, but the outcome of doing so would be catastrophic. Watch the video to the right/above to get a better feel for this problem.

    These weak layers produced a set of historic avalanches in the past two weeks (map, list). Aside from the crowns and debris from these avalanches, you aren't likely to encounter signs of instability from these buried weak layers today. If you don't dig down, the snow will "feel good". If you want to see this weak snow for yourself, pull out your shovel. You'll find crust+facet combinations on sunny slopes and small facets on shaded slopes. But don't expect to gain a lot of information by digging; snowpack tests are unreliable for weak layers underneath thick, dense slabs of snow.

    Tracks on a slope are not an indication of stability. Avalanches may be triggered after many skiers or riders have traversed a slope. The first sign of instability may be the large, destructive avalanche you trigger. These slides may break much wider and much further above you on the slope than you expect. They can be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

    These types of avalanches are hard to deal with. The only way to eliminate your risk of encountering one of these beasts completely is to avoid avalanche terrain and terrain exposed to hazard from above. I know, that's not satisfying to hear. You can reduce your risk by avoiding slopes steeper than about 35 degrees—especially large avalanche paths and those with ugly consequences if you are caught in a slide. Remember that even small slopes can carry high consequences when we are dealing with very dense slabs.

    ADDITIONAL DISCUSSION: Be on the lookout for small, sensitive slabs of wind-drifted snow at upper elevations. A bump in wind speeds and additional snow falling this afternoon will help these slabs to grow in size and to remain sensitive to your weight. Look for signs of wind-transported snow (dunes, drifts, and ripples on the surface). Cracks shooting out from your skis or machine are indications that you've found a reactive slab.

Avalanche Discussion

You will be faced with two very different categories of avalanche hazards today. At the surface, you'll find fresh wind slabs that will be reactive to your weight and loose snow avalanches that will be easy to trigger. These types of problems are relatively easy to identify and manage. Further down in the snowpack, you'll find the weak layers that produced the impressive, widespread, and in places historic avalanche cycles earlier in the month.  Identifying which slopes may avalanche or where you need to be on a slope to produce an avalanche is essentially impossible. The only surefire management strategy for this type of problem is avoidance.

If you're feeling like you have to enter big, steep avalanche terrain today, I recommend spending some time contemplating the consequences of triggering an avalanche on the weak layers buried in our snowpack. It can be hard to wrap one's head around the destructive power of these meaty slab avalanches. Fortunately, mother nature has already done the work of imagining for us. Find a large crown and look at the debris below. There are large piles of debris littering our mountains, you probably won't have to look hard to find one. These are the types of avalanches that are on the table. The weak layers are deeply buried and impacting them with our weight is not an easy task. It's more likely than not that you won't trigger a massive avalanche on the slope you are planning on riding or skiing. Unfortunately, if the dice come up snake eyes and you do trigger one of these slides, there is a good chance that you won't survive. 

Dealing with low likelihood/high consequence problems is incredibly frustrating. It is late March and we are all ready for some bigger terrain, but that terrain isn't ready for us. Our travels in the mountains are driven by the snowpack, not the calendar. We've made it to spring, but the snowpack is still wearing her winter hat. When you head into the mountains today, you'll find a dry, cold snowpack complete with weak layers buried underneath meaty slabs of snow. With our snowpack behaving like winter we are well served to follow her lead, she is the boss.

Watch Ethan's Weekend Update to get caught up on what happened last week and for a sense of where we are headed this weekend.

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