Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

Fri
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Avalanches large enough to bury a person are most likely at upper elevations and on shaded middle-elevation slopes facing W-N-E. You may not observe obvious warning signs like snowpack cracking or collapsing before triggering a slide.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    You could trigger 1.5-2.5 foot thick avalanches that fail on buried persistent weak layers near the bottom of the snowpack. These weak layers exist on upper elevation slopes and most middle elevation slopes facing W-N-E. You'll find a stack of weak, sugary facets on shadier slopes. On sunnier slopes, the weak layers present as a variable series of crusts and facets. 

    Obvious signs of instability, like cracking and collapsing of the snowpack, have decreased. This doesn't mean the problem has gone away. Tracks on a slope are not indicators of stability — Several skiers or riders can descend a slope only to have the next person trigger an avalanche.

    The best way to manage this problem is to avoid avalanche terrain where denser slabs rest above weak, older facets and crusts. Short of that, you can reduce your risk by avoiding recently wind-loaded slopes, large avalanche paths, and those with ugly consequences if you are caught in a slide. 

Avalanche Discussion

When discussing the complexity of lingering persistent slab problems, a mentor of mine was fond of the adage, "The danger is quick to rise and slow to drop." Then he'd smirk and shrug his shoulders with an air of that's just how it is. Personally, I've found this simple saying helpful. It snaps me out of trying to find the "answer" (is this slope safe?) and reminds me to sit with and accept the uncertainty of travel in avalanche terrain.

Persistent slab problems gradually stabilize over time following a loading event. The chance of triggering large avalanches slowly decreases each day without significant snowfall or wind-loading. Persistent weak layers, like the ones we have this season, can produce avalanches for weeks after a storm. 

It's been several days since the last large reported avalanche, and obvious signs of instability like snowpack collapsing are on the decline. We are firmly in the mentally challenging slow-to-drop realm, and shortcutting the process can be tempting. We know conditions are improving, and our tendency to look for information that's consistent with this belief (like previous tracks on a slope) can be overwhelming.

Don't rush the process. Some folks are selectively dipping their toes into some smaller avalanche terrain with clean runouts, but we're far from diving head-first into complex terrain. 

Régions couvertes