Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

Wed
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Very dangerous avalanche conditions exist. The combination of heavy snowfall and strong wind is creating slabs that will be large and easy to trigger. This additional load is also adding stress to weak layers buried 2-3 feet deep in the snowpack. Large human-triggered and natural avalanches are likely today—travel in avalanche terrain is not recommended.

COVID-19: The medical system cannot spare the resources required to care for injured backcountry skiers and snowmobilers. Search and Rescue will be delayed or unavailable. Please recreate responsibly close to home and follow social distance requirements to protect yourself and others.  

Problèmes avalancheux

  • Storm Slabs

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

    Intense rates of precipitation can build soft slabs, even in areas sheltered from the wind. It has been snowing at a rate of one inch of snow per hour for the past ten hours in this zone and I expect that a number of these storm slabs may have failed naturally overnight. They will be much thicker and more reactive in upper elevation terrain where the wind has helped them to grow, but you can expect to find these slabs as soon as you leave your car. Be wary of even small terrain features and pay attention to terrain traps such as gullies and creek beds at the bottom of slopes. On slopes that directly face the sun, slabs are resting on stiff, icy crusts. Any slide you trigger in these areas will pick up speed quickly as it travels downslope. 

  • Persistent Slabs

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

    Weak layers of snow buried in the upper 2-3 feet of the snowpack produced two human-triggered avalanches this weekend (photo, photo). Both of these avalanches failed before the heavy load that was added last night. The culprit weak layers have been sugary facets that developed earlier this month during clear weather between storms. These layers exist across our advisory areas. The ongoing storm added a significant amount of weight to these layers last night, further destabilizing the snowpack. You'll be most likely to encounter this problem on slopes that face E-NE-N-NW.

    Triggering one of these slides is more likely in wind-loaded terrain, but is possible in sheltered terrain as well. Persistent slab avalanches fail in ways that catch even experienced backcountry travelers by surprise. They may break much wider than you expect, wrapping around terrain features that typically confine wind and storm slabs. These types of slides can be triggered remotely—from flatter terrain above, below, and to the sides of avalanche starting zones. Building a wide safety margin into your travel plans is essential. 

Avalanche Discussion

Today is the first day in two and half months that we have HIGH danger in our forecast area. The best way to overload a snowpack is to throw a rapid load of snow at it. Intense precipitation rates accomplish this well, as do strong winds. Right now we've got both of those things going on. The ongoing pandemic reminds us that the world can shift underneath your feet. The storm in progress should remind you of the same. Its been a weird winter to say the least, one marked by an overall lack of snowfall and long periods of relatively stable conditions. Today is different. If you choose to go into the backcountry, be prepared to deal with the full spectrum of mid-winter avalanche hazards. Dial back your ambitions and build a wide safety into the way you travel in the mountains. And remember that now, more than ever, your actions have consequences that affect the community around you.

 

Régions couvertes