Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Two human-triggered avalanches occurred near Galena Summit yesterday. Both involved wind drifted snow in terrain exposed to the wind, and similar slides are likely again today. Larger avalanches involving layers of weak snow buried 1-3' beneath the surface are most likely in steep, wind-affected terrain, but are possible in sheltered terrain as well. These types of slides can be triggered from long distances away from steeper slopes. You can significantly reduce your risk of triggering avalanches today by sticking to gentler terrain sheltered from the effects of the wind.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Several weak layers exist in the upper few feet of the snowpack. Yesterday's remotely triggered slide  (pictured at right/above, details here) likely failed on one of these weak layers. Triggering an avalanche involving these layers remains a real possibility today. You're most likely to do this in steep terrain that has been recently wind-loaded, but this problem exists in sheltered terrain as well. These weak layers involve either a crust+facet combination, small facets without a crust, or surface hoar. You'll need a slope that faces the sun in order to have the crust, but the facets and surface hoar can be found around the compass. 

    We've looked for and found these layers across our forecast area, but they don't exist on all slopes. In places, the sun and the wind helped to mute the effects of some of these layers, but in others they are well preserved and quite concerning. Avalanches on persistent weak layers can be triggered from long distances away from steeper slopes ("remote triggering"). They can break wider than you might expect and pull back into gentler terrain above steeper slopes. 

    Want to significantly decrease your risk of triggering a large avalanche today? You can do so by sticking to gentler terrain, free of overhead hazards, that is sheltered from the effects of the wind. As a bonus, you'll also find the best skiing and riding here.

    ADDITIONAL DISCUSSION - WEAK SNOW NEAR THE GROUND: A layer of weak, faceted snow exists near the base of the snowpack. This layer has produced hundreds of avalanches this season. The most recent triggered avalanche involving this weak snow happened Friday in the Baker Creek drainage (photo at right/above, details here). An even larger slide was remotely triggered 6 days ago (before the recent storms) by riders in the White Clouds (photos and details here). In this zone, this weak snow is now buried 2-4 feet down, beneath a dense slab of snow. Impacting deeply buried weak layers with your weight isn't easy, but the consequences are grave. You're most likely to trigger this layer in steep, wind-affected alpine terrain where snowpack depths are variable. Here, you'll have better access to this weak snow. This is exactly the type of terrain where I triggered the avalanche in Baker Creek on Friday. Digging down to this weak snow with the track of your sled is another "great" way to impact this deep weak layer.

    (12/31/2022) This large avalanche was remotely triggered from hundreds of feet away. It failed on a S-facing slope at 9,500' near Mushroom Ridge, which is near Galena Summit. It failed in upper elevation wind affected terrain, and likely involved a persistent weak layer in the upper snowpack.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–2.5

    Two human-triggered avalanches occurred near Galena Summit yesterday (view details and photos in our avalanche database). They both failed near the boundary between middle and upper elevations, in terrain that is exposed to the effects of the wind. In the past week, 24-40" of snow (2.5-3.5" snow-water equivalent) fell here. Snowfall was accompanied by winds blowing from varying directions and at varying speeds. This combination built both hard and soft slabs in many different locations. Some of these have had time to bond to the surfaces they sit on, while others remain unstable, as yesterday's triggered avalanches prove. 

    Look and feel for evidence that the wind has been at work as you travel. Are you seeing textures on the surface, like drifts and dunes and ripples? Is the snow you are traveling through becoming denser or deeper? These are all signs the wind has been transporting snow. Remember that these indicators of wind transport may be masked by new snow on top of older slabs. Expect to find wind-affected snow in upper elevation terrain and in exposed middle elevations. Cracking and collapsing in fresh drifts are sure signs you're traveling on a sensitive slab. Slabs are most likely near and along ridgelines, and near terrain features like gullies that get cross-loaded by the wind.

    Triggered slabs have the possibility to step-down to the deeper weak layers described above. The result would be a much larger and more destructive avalanche.

Avalanche Discussion

New Year, New You. Same Snowpack, Same Game.

Yesterday, two human-triggered avalanches near Galena Summit were reported. One caught and carried a very experienced skier. The other was remotely triggered from hundreds of feet away, likely by a skier and rider above, though details are murky. This second slide wiped out fresh ski tracks and came close to a large party that was ascending the slope below. When I hear about these types of events I find myself thinking, how much worse could this have been? Close calls like this are vivid reminders that this game we are playing is a serious one.

We head into 2023 with a snowpack that is marked by complexity. A widespread layer of weak snow at the base of the snowpack has kept the Avalanche Danger elevated throughout the season. Big storms pushed this weak snow to its breaking point and produced widespread avalanche activity. These storms also buried new weak layers that are now located in the upper few feet of the snowpack. Unlike the weak snow near the ground, which is ugly just about everywhere, the more recent weak layers are much more variable. They seem to be at their worst on slopes that face the sun, where small facets are sitting on top of a crust. However, they have also produced avalanches, collapses, and unstable snowpack test scores on shaded slopes. The overlapping instabilities and hazards posed by this patchwork of weak layers are challenging even for professionals to keep track of. 

I think of entering avalanche terrain as "playing the game." When we choose to enter terrain where triggering avalanches is possible, it is important that we do so consciously, and that we are honest with ourselves about the potential outcomes. I'm not telling you not to enter avalanche terrain, that isn't my job. I'm trying to help you understand what type of game you are playing when you choose to do so. It is a game with odds that are impossible to calculate, and with outcomes that can range from the best run of your life to the life-shattering loss of your partner. I have experienced both ends of this scale. 

Think about yesterday's near-misses when you are in the mountains today. Have an honest conversation with your partner on the drive to the trailhead about the game that you are planning to play. Spend some time imagining what would happen if you or your partners were caught in a large slide in the terrain you are choosing. If you choose to enter avalanche terrain you are choosing to accept the full range of outcomes. Be honest with yourself about what that looks like. 

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