Bulletin d’avalanche

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Sat
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 7 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Dangerous avalanche conditions exist. Human-triggered avalanches are likely, especially in wind-loaded terrain. Cracks shooting from your boards or sled are a sure sign that you’ve found a sensitive slope. Recognize that you could trigger avalanches from above, to the side, or from below steeper terrain.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2

    Widespread weak layers exist throughout this zone. Last weekend’s storm produced natural avalanches and widespread signs of unstable snow such as rolling collapses and shooting cracks – we should expect no different today. This problem will be especially dangerous where active wind-loading is occurring. In these areas, natural avalanches are 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.

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Expect to find 1-3’ thick wind slabs at upper elevations. These slabs have to potential to fail naturally as moderate NW wind continues this morning. You’re most likely to find these slabs on the downwind side of prominent terrain features like exposed ridgelines, rock outcrops, and mid-slope gullies. Smaller wind slabs, once triggered, have the potential to break into the deeper, weak, faceted snow near the ground.

Avalanche Discussion

An inch of SWE and continued moderate NW wind will put the weak layers of the Galena Summit & Eastern Mountains Zone 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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