Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
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Danger d’avalanche

Mon
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

    Two prominent weak layers capable of producing destructive avalanches exist in our snowpack:

    1.  Large, 1-3 foot thick slab avalanches will be easy to trigger on many slopes today. These slides can break hundreds to thousands of feet wide and will produce piles of debris plenty large to bury you. Slabs will be at their largest, most destructive, and easiest to trigger in areas where the wind has been at work adding extra weight and strength to these slabs. However, enough snow accumulated this week that we are also worried about the possibility of triggering these avalanches in sheltered terrain. Prominent weak layers that formed during the December drought (surface hoar, facets, crust+facet combos) underlie these slabs. Avalanches involving these can be triggered from long distances away from steeper slopes.   Even smaller slopes at lower elevations can make avalanches with a snowpack like ours. Expect to see and to be able to trigger avalanches in unusual locations today. 

    2.  A layer of weak, early season snow forms the base of the snowpack in some locations. This layer exists on all upper elevation slopes and most shaded, middle elevation slopes (those facing W-N-E). Avalanches that fail on this layer will wipe out the entire season's snowpack and are likely to be unsurvivable. These will involve entire alpine bowls, with crowns spanning numerous aspects and wrapping around thousands of feet of terrain. These are the types of avalanches that can destroy vehicles and bury your house. You can trigger these enormous slides from the valley bottom. 

    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. 

    (1/11/2024) This large avalanche was remotely triggered in the Headwaters drainage. Ben and his partner on Thursday afternoon were over 100 feet away, on the opposite side of the ridge when they triggered this collapse and resulting avalanche.  This avalanche ran through some very hazardous terrain and was plenty large to bury a person.

  • Wind Slabs

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

    Last 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

These are the types of days when avalanche accidents happen. It will be beautiful out there and we are a pack of hungry dogs staring at a meal of deep powder. Unfortunately, the snowpack in our mountains is anything but friendly. We are on the heels of a widespread natural avalanche cycle. The mountains aren't falling down quite like they were earlier this week, but you are likely to trigger a large slab avalanche on many slopes today. If you are choosing to enter avalanche terrain, you are choosing to accept this risk.

A series of storms this week brought feet of snow to the mountains, accompanied by the biggest wind event of the season. Natural avalanche activity was widespread on Friday, and large human-triggered avalanches were reported yesterday. 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. 

I encourage you to take a conservative approach to the mountains today. If you are thinking about skiing or riding a steep slope, remind yourself that you are likely to trigger a large avalanche and then picture the consequences of that happening. There is a lot of great riding and skiing to be done on lower angle slopes that are free from overhead hazard today. Try to find a place like this to play while we let the snowpack adjust.

Régions couvertes