Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 7 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Light snowfall and wind will continue the threat of triggering slab avalanches. You're most likely to find trouble where the wind has formed fresh drifts or stiffened the snow in the upper 6-12 inches of the snowpack. While less likely, avalanches could break 2-3 feet deep on older weak layers. Because these weak layers are both widespread and difficult to evaluate on a given slope, picture what would happen to you if an avalanche released before skiing or riding large, steep slopes. 

Problèmes avalancheux

  • Persistent Slabs

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

    The steady trickle of new snow is not giving the snowpack the "vacation" it deserves. While triggering a large slab avalanche that fails on surface hoar or depth hoar buried 12-30" deep is not likely, it remains a possibility. 

    To reduce the chances of triggering an avalanche, avoid areas where hard, "drummy" or hollow sounding snow exists. Before committing to skiing or riding steep, consequential slopes, dig a quick hole in the snow. Is there a slab (stiffer snow) in the upper foot of the snowpack? If so, you may be able to trigger shallow avalanches. Next, look for the telltale grey stripe (buried surface hoar) or crumbly, sugary snow near the ground (depth hoar). These layers could produce large avalanches you don't want to tangle with, and they behave unpredictably:

    • Tracks on the slope do not mean it's stable, the 3rd, 5th, or 10th person down the slope may be able to trigger it.
    • Slides could span wide distances.
    • You might be able to trigger avalanches remotely: from gentle terrain above, below, or to the sides of steep slopes. 

     

    Additional Discussion

    In exposed upper elevation terrain, expect to encounter fresh drifting and wind slabs. The slabs may grow large enough to pose a hazard by themselves, and many lie above the persistent weak layers described above.  Fortunately, the drifting should be easy to spot and avoid. 

Avalanche Discussion

It seems like we're stuck in a holding pattern, circling above the airport. Are we going to land (get to ride and ski in avalanche terrain without being scared of triggering large slides on the buried surface hoar or depth hoar layers), or are we going to be diverted to another airport where we don't want to be (snow and wind tips the scales and makes large avalanches likely)? Unfortunately, I don't think we'll get a definitive answer today.  

The light snowfall and wind will stress the old weak layers enough to keep the stability see-saw in limbo. A week of high pressure would tip us to the "stable" side, and a big storm would probably firmly ground us on the "unstable" side; we're stuck in "conditionally stable" purgatory. What does that mean? You could ski or ride many slopes without incident, and you could trigger an avalanche large enough to kill you or change your life on some slopes. 

What really stinks: it's almost impossible to say with any kind of certainty how far the see-saw is tipping on a given slope that has the buried surface hoar of depth hoar layers. Local ski guides and the SAC forecasters are leery of testing the see-saw (skiing large, steep avalanche prone slopes). I'd love to have a pack full of explosives to test the inviting-looking slopes I see every day I'm out, but that's not happening. Without explosives, I can't predict with enough certainty whether that pristine, 38-degree slope will slide or not. So, I'll keep enjoying great riding and sliding conditions on slopes less than about 30 degrees until mother nature craps or gets off the proverbial pot. Hopefully, the weekend storm delivers and gives us a clear signal where we stand.   

Régions couvertes