Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

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

Points saillants

You can easily trigger large avalanches on many slopes today. Slides can be triggered from long distances away from steeper slopes, breaking well above you and cascading down to the slopes below. Avalanches that break into deeper weak layers in the snowpack are likely to be unsurvivable. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–3

    You are likely to trigger large, destructive avalanches failing on weak snow in our snowpack. Importantly, these avalanches are pulling back into lower angled terrain above steeper slopes. These slides can be triggered from a distance away — giving you a reason to increase your travel margins. Two types of these slides can occur today:

    1) A 1-3 foot thick slab avalanche large enough to bury you will be easy to trigger on many slopes today. Avalanches will break hundreds to thousands of feet wide across entire slopes and span multiple aspects. These slides will be at their largest and most destructive in areas where the wind has deposited additional snow. But sheltered slopes are in no way safe: dozens of these avalanches have occurred in wind-sheltered terrain, and on smaller slopes at lower elevations such as road cuts. 

    2) Avalanches mentioned above can step down to a layer of weak snow near the base of the snowpack creating slides that are likely unsurvivable. These slides will move the entire snowpack downhill. This layer of weak snow exists on all upper and most shaded middle-elevation slopes (W-N-E). 

    The most important thing to know about these avalanches is that you can easily trigger them from long distances away. They can break well above you on the slope and can be triggered from flat terrain at the base of steeper slopes. 

    (1/14/2024)

    Many of the  avalanches that failed this week have pulled back onto relatively low angle terrain. The slides in this image are a great example. These avalanches failed on E-facing slopes at 8,100-8,300 feet near McDonald Peak in the Sawtooths. 

    Photo: Ben VandenBos

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–1.5

    Saturday night's storm brought 4-8 inches of low-density snow to this zone. Winds have generally been light here, but you may find some small, sensitive wind slabs if you head into upper elevation terrain. In sheltered areas, expect today's fresh snow to sluff readily on steeper slopes. These sluffs will happen naturally in steep terrain receiving direct sunshine. Small wind slabs and sluffs can be "great" triggers for the persistent slab problems described above. 

Avalanche Discussion

LARGE HUMAN-TRIGGERED AVALANCHES ARE LIKELY ON MANY SLOPES

In the past five days, we went from zero to three avalanche fatalities in the U.S. this season. Days like today are when avalanche accidents happen — and I don't want you to be part of that statistic. Sunshine, fresh powder, and friendly winter temperatures invite us into the mountains today, but don't be fooled by their snow-covered allure: large human-triggered avalanches are likely on many slopes. If you enter avalanche terrain today, you are accepting the possibility of being unlucky number four.

Peering into the mountains while driving to the trailhead, it might take a skilled eye to see the crowns of avalanches from our near-historic avalanche cycle that we are on the tail end of due to wind blowing new, low-density snow into these paths. Again, don't be fooled: local avalanche professionals reported seeing 100's of large natural avalanches in recent days. While many of these natural slides have run their course in the past few days, large human-triggered avalanches are still likely.

A series of storms brought feet of snow to the mountains, along with the biggest wind event of the season. All observations report widespread cracking and collapsing of the snowpack, which are clear indications of instability. While the likelihood of encountering large natural avalanches today is lower than it was during the storm, your likelihood of triggering one of these slides remains much too high for comfort today. Conditions are at their worst in areas where the wind built thicker slabs during this week's storms. Thanks to the low density snowfall from last night, it will be hard to visually determine if the wind has been at work on any given slope. Thanks to the strength of Friday's winds, it's safe to assume that most slopes have some wind stiffening. 

Today can hold either the recipe for disaster, or new lighthearted memories with your partner. A day of low angle powder ending in both you and your partner returning home at night is always better than the alternative. I encourage you to be conservative in your decision-making, and remain patient with our snowpack. 

Régions couvertes