Boletín de aludes

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Sawtooth Avalanche Center
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Peligro de aludes

Sun
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You could trigger a 1-3 foot thick avalanche on slopes that are exposed to the wind. To significantly reduce your odds of triggering a slide, steer clear of steep terrain with evidence of recent wind loading such as cornices, pillows, and drifted snow. 

Problemas de aludes

  • Persistent Slabs

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

    A variety of weak layers exist in the upper 3' of the snowpack (observation). We've found these layers in several snowpits on a variety of aspects (video above/right). They appear to be most problematic on middle and upper elevation sunny slopes where they exist as a crust+facet combination. These layers also exist on shadier aspects where an obvious crust may not be present and where we're occasionally finding surface hoar (photo). 

    The exact location, makeup, and sensitivity of these layers vary and are difficult to pin down. The complexity and spatial variability of this problem make slope scale stability assessment a highly uncertain task. The safest bet is to assume one or more of these layers exist and are capable of producing a large avalanche. 

    These layers are slowly healing. Slopes steeper than about 35 degrees, and/or those with recent wind loading will take the longest to stabilize. Therefore, avoiding steep, wind-drifted terrain is an effective way to reduce your odds of triggering a large avalanche. 

    ADDITIONAL DISCUSSION: You may find sensitive wind drifts at upper elevations. Look for evidence of fresh windblown snow such as drifts, pillows, and new cornice growth. I'd expect these to be small, but given the weak snow surfaces they formed on, they could be sensitive to your weight. 

Avalanche Discussion

Today's fair weather won't affect the avalanche danger. The persistent weak layers in the upper 3' of the snowpack are slowly healing, but as the name "persistent" implies, the overall picture today is much the same as yesterday. Stability is improving, but as Chris pointed out yesterday, "conditions are still ripe for getting surprised". Why? The complex distribution of weak snow in our upper snowpack means stability could change dramatically from slope to slope. Today, you likely won't observe any obvious "red flag" warning signs that conditions are dangerous. When the danger is not "in your face" it can make choosing a safe place to play a much harder task. This is especially the case when we're dealing with overlapping and sporadically distributed persistent weak layers. 

Today, the complexity of the snowpack and therefore my terrain selection remains the same. When faced with uncertainty in the backcountry, choosing safer terrain is the only way to reliably reduce your risk. That means ruling out steep, upper elevation, wind-loaded slopes—a message we've hammered home over the last week, and one remains the best advice again today.

Be sure to check out JP's Weekend Update for a recap of the recent natural and human-triggered avalanches over the past week.

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