Bulletin d’avalanche

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
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

It remains possible to trigger large, 1-3 foot thick slab avalanches. Buried weak layers underneath these slabs produced natural avalanches in the past two days. To reduce your risk, choose gentler slopes and avoid terrain where the wind has built slabs and added stress to the weak snow below.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    It's been nearly five days since the snowpack in this area has been stressed by a significant loading event. Unfortunately, the type of weak snow that we’re dealing with this year isn’t the sort to heal quickly. Although very little snowfall has been recorded in the past days, the snowpack continues to give us clear signs that it is unstable.

    Yesterday, in the Baker Creek drainage, I observed a slab avalanche that appeared to have failed naturally that day (photo at right). Sun Valley Heli Ski staff reporting seeing a large avalanche that likely failed sometime on Saturday (photo here). Both of these avalanches are clear indicators that triggering slides on our buried persistent weak layers continues to be a worrisome possibility.

    You can reduce your exposure to the hazard posed by this problem by choosing gentler slopes and avoiding terrain where the wind created slabs during and following last weeks storms and added stress to the weak snow underneath.

    ADDITIONAL DISCUSSIONAging wind slabs in exposed upper elevation terrain are becoming less reactive as time passes. However, if you do trigger one of these smaller slabs it may be capable of triggering a more sizable slab as it travels downhill. This appears to be what happened with the avalanche that Sun Valley Heli Ski staff reported seeing yesterday (photo above).

Avalanche Discussion

If you are getting tired of reading about and dealing with persistent weak layers, you might want to think about relocating to an area with a different snow climate. Long-lived layers of weak snow are the name of the game around here and this season is no different.

Avalanches are more likely to occur when there is something to trigger them. This trigger can take many forms  — a falling cornice, a wayward herd of elk, and most importantly, you. Yesterday, multiple avalanches that failed within the past 24 hours were observed. These avalanches failed naturally, in the absence of any obvious trigger. These natural avalanches are a clear sign that the snowpack continues to be unstable. If it’s true that time heals all wounds, our snowpack is clearly in need of some more time.

Details from Wednesday's Avalanche Accident in Baker Creek:On Wednesday, January 15th, 2020, a snowmobiler was caught and killed in an avalanche in the Baker Creek drainage, approximately a half-mile northeast of Baker Lake. We visited the site Thursday to collect data on the avalanche. This video contains preliminary information collected during the site investigation; a full accident report will be published soon.

The avalanche released at an elevation of 9200 feet on a south-facing, wind-loaded slope. The slab broke 2-3 feet deep, 250-300 feet wide, and ran just over 600 vertical feet. The slope angle of the start zone was around 33 degrees, but the slope steepened significantly below the fracture line. The avalanche was triggered from lower on the slope, well below the crown line of the avalanche, and released on a persistent weak layer of faceted snow in the middle to lower snowpack. The avalanche debris range from 3-8 feet deep.

Régions couvertes