Boletín de aludes

Banner Summit

Sawtooth Avalanche Center
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Peligro de aludes

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

Lo esencial

Avalanches large enough to bury a person are most likely at upper elevations and on shaded middle-elevation slopes facing W-N-E. You may not observe obvious warning signs like snowpack cracking or collapsing before triggering a slide.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2.5

    You could trigger 1.5-2.5 foot thick avalanches that fail on buried persistent weak layers—sugary facets or crust + facet combinations—near the bottom of the snowpack (see photos and videos below). These weak layers exist on most upper elevation slopes and on middle elevation slopes facing the northern half of the compass (W-N-E aspects). You can verify the presence of this layer by digging a quick hole. The weak facets will appear grey and feel loose and crumbly.

    Most folks are reporting some form of snowpack cracking or collapsing (orange dots here). These are clear indicators that the snow you're traveling on is unstable. However, a lack of this feedback is not your ticket to green-light a slope. The best way to avoid this problem is to steer clear of steep slopes where these old facets exist. Persistent Slab avalanches can break wider and higher on slopes than expected. You could remotely trigger avalanches from gentler terrain below, above, or to the sides of steep slopes. 

Avalanche Discussion

Is the risk worth the reward? This is the very personal question we all face when traveling through the mountains. Often, the reward is obvious: a powder-filled couloir or an un-tracked face. However, the risk needs assessing, and it's not always clear. When the mountains are falling down around us, the choice is obvious—come back another day. When the storm passes, we're left with clues. Recent avalanches and cracking and collapsing of the snowpack are nature's not-so-subtle reminder, "Hey, you better check yourself; it's spooky out here." But as these warning signs diminish, the thought arises again: is the risk worth the reward?

This is where our assessment of risk gets tricky. It's also where a persistent slab problem forks from a simpler storm slab or wind slab problem. Persistent slabs, as the name implies, can be triggered days and even weeks after a storm. While your odds of triggering a persistent slab decrease over time, the process is slow. Currently, we're entering a frustrating grey area that sits between obvious danger and safer conditions. A grey area that's led to many avalanche accidents, and understandably so. The snowpack structure is ugly on many slopes. Some of them will remind us of that fact, but others may not—until it's too late.

Areas of thin snow cover and recent sunny, warm weather will naturally nudge you to the colder, drier snow on shaded slopes and deeper snow cover of upper elevations. These are the exact slopes where this problem is at its worst. So, is it worth it? What are my odds of triggering this start zone? The answers to these questions are unknowable, but admitting that fact is a powerful motivator. Our uncertainty allows us to pivot to factors that remain in our control. Choosing slopes devoid of weak snow at the base of the snowpack is the best way to reduce our risk. Short of that, you can avoid inherently more dangerous terrain like big avalanche paths or slopes that end in terrain traps like trees or a creek bed. If you're considering skiing or riding steep terrain where this problem exists, take a moment to consider the consequence of being caught in a slide. 

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