Bulletin d’avalanche

Galena Summit & Eastern Mtns

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 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You may be able to trigger avalanches in both wind-affected and sheltered terrain. In areas exposed to the wind, you could trigger hard or soft drifts or slabs that formed over the past several days. In areas more protected from the wind, 1.5-2 foot thick avalanches are possible on shady slopes. Loose snow avalanches are possible as the sun peels snow from warm, rocky, extreme terrain. Even small slides can have big consequences on slopes with cliffs, trees, and terrain traps.

Problèmes avalancheux

  • Persistent Slabs

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

    Multiple weak layers exist in the snowpack, and triggering a persistent slab avalanche remains possible. The distribution, sensitivity, and depth of these layers vary across the zone. Here are two distinct scenarios:

    1. Surface hoar: A skier triggered a slide near Galena Summit Sunday (view report). The 1-2' thick avalanche failed on a layer of buried surface hoar. This layer is responsible for several skier and rider triggered avalanches over the past two weeks. This layer is most problematic on slopes facing NW-N-NE that are steeper than about 35 degrees.
    2. Older weak layers: Crusts and/or facets, and occasionally surface hoar, exist deeper in the snowpack. These are buried beneath dense, 2-4' thick slabs—making them difficult to trigger but capable of producing very dangerous avalanches. While triggering them is unlikely, it can't be ruled out in rocky, wind-affected, alpine terrain (example). Slopes like these have variable snow depths, with thinner areas of the snowpack that allow us to impact deeper weak layers.

    Overlapping, variable weak layers make avalanche conditions hard to predict. The single best way to reduce your risk is by avoiding slopes greater than about 35 degrees. Consider the consequences of going for a ride. Even small slides can have bad outcomes if they lead to trees, cliffs, or a creek bed.

     

    (1/30/2023) This 1-2 foot thick, skier-triggered avalanche failed on a layer of buried surface hoar. Surface hoar is frequently found in shady, partially treed locations like this. N-NE aspect near 9100' in the Salmon River drainage near Galena Summit.

  • Wind Slabs

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

    Last weekend's snow and northerly wind formed soft 1-1.5' thick slabs in exposed terrain. A handful of small natural wind slab avalanches occurred over the weekend (Galena Pass, Banner). Monday, we spotted a large wind slab in the Soldier Mtns (photo). 

    This problem is most dangerous at upper elevations where slabs are larger and more widespread. Look for them near ridgelines, on the sides of gullies and chutes, and near prominent terrain features. In some steep rocky terrain, you'll also find slabs where snow has cascaded down and accumulated below cliffs (example).

    Cracks shooting out from your skis or sled are an obvious sign of instability (example). Watch for drifts, dunes, and ripples on the snow surface. Older hard slabs can have a smooth, chalky appearance and feel and sound hollow, like a drum. Wind-deposited snow will be stiffer and keep your skis or snowmobile closer to the surface.

    (1/29/2023) This recent small wind slab released naturally on Titus Ridge near Galena Summit. It failed on a E/NE-facing slope at 9,600'.

Avalanche Discussion

Here's a quick top-down overview of the snowpack and associated avalanche concerns:

Near the Surface

  • Loose Snow Avalanches: Today's warm temperatures and direct sun may peel soft snow from wind-sheltered, rocky, extreme terrain. Although mostly small, some of these slides will collect enough snow to sweep you off your feet or bury you in a depression. Keep this problem in mind if you're traveling on or beneath large, rocky slopes this afternoon. 

Upper Snowpack

  • Wind Slabs: A few generations of wind slabs formed in the past week. The most recently formed slabs are softer and may be more reactive to your weight. However, the large, recent slide in the Soldier Mtns probably involved rock-hard snow that drifted onto the slope last week; triggering beasts like that is not entirely out of the question. Triggered wind slabs can be effective triggers for deeper weak layers in the snowpack.
  • The layer of surface hoar that was buried in early January hasn't seen as much of a load in this area and lacks a slab on many slopes. In most locations, you need the additional stiffness and weight from wind-loading for this layer to be a problem. However, Sunday's triggered avalanche near Galena Summit failed on a slope that is typically sheltered from the wind.

Middle and Lower Snowpack

  • Three to five feet of snow are on the ground in this zone. Weak layers buried in November and December are closer to the surface here, and triggering a slide involving these weak layers remains a possibility on slopes steeper than about 35 degrees where the wind has created a variably thick snowpack.

The consequences of triggering avalanches can vary significantly. Triggering a small slide in terrain free of rocks, trees, and terrain traps is much less dangerous than triggering a slide in extreme, rocky, treed terrain with a terrain trap at the bottom. Think about the consequences of being caught in a slide before committing to skiing or riding in sizeable avalanche paths. 

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