Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sat
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 7 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Very dangerous avalanche conditions exist. The combination of wind and 1-2 feet of new snow is pushing a weak snowpack to its breaking point. Natural avalanches are likely, especially in wind-loaded terrain. Avoid all steep slopes and the areas beneath them. Recognize that you could trigger avalanches from above, to the side, or from below steeper slopes.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2

    Widespread weak layers exist throughout this zone. Last weekend’s storm produced natural avalanches on these layers and we should expect no different today. This problem will be especially dangerous where active wind-loading is occurring. In these areas, natural avalanches are very likely.

    Today is not the day to try to thread the needle. Persistent slab avalanches may break wider than expected, spanning multiple terrain features. Slides may be triggered from a distance – including from the sides or below a slope. Travel in avalanche terrain is not recommended.

Avalanche Discussion

One to two inches of SWE and continued moderate NW wind will put the weak layers of the Sawtooth and western Smoky Mountains to the test. Here’s a quick rundown of the most prominent problem layers.

September and October Depth Hoar:This layer at the bottom of the snowpack has produced avalanches and obvious signs of instability since Thanksgiving. It's most widespread in upper elevation and middle elevation terrain, but you should assume it's present until proven otherwise.  You can dig quick holes to search for it, and it's easy to identify. Look for loose, sugary snow that appears as a grey layer near the ground.

Thanksgiving Storm Snow: This layer weakened significantly in the cold, clear weather that followed and tall crystals of surface hoar formed in many areas. Crusts developed on sunnier aspects and at lower elevations. This layer (buried on December 7th) was responsible for several small slab avalanches last weekend in the Sawtooths, Smokys and Boulder Mountains. 

To top it off,  the snow surface beneath the current storm snow harbored layers of facets and surface hoar. It's yet to be seen how this layer will react, but we'll certainly know more today. On Wednesday, Ben and I backed off our planned route in the Smiley Creek Drainage of the southern Sawtooths. Remotely triggering a persistent slab avalanche felt like a real possibility, and that was before this storm. Figuring out the relative strength and distribution of these weak layers is complicated, but the take-home point is simple. Our snowpack produced natural and human-triggered avalanches when it was loaded last weekend and today we should expect the same.

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