Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Dangerous avalanche conditions exist—particularly on steep slopes with stiff deposits of wind-drifted snow. The danger will remain elevated as snowfall and wind-drifting continue through tomorrow. Avalanches can be triggered remotely—from below, above, and to the sides of steeper terrain.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    "Weak snow near the ground" is the mantra of the winter. Two months ago, we buried a widespread, thick layer of facets. This layer has been responsible for the vast majority of the avalanche activity we've seen since. Unfortunately, it's shown few signs of improvement. 

    However, one factor that's helping our cause is its burial depth. As this layer becomes more deeply buried it becomes harder to impact. You'll find this layer under a stout ~3' thick slab of snow. In many portions of the zone, we're headed toward a low-probability but high-consequence avalanche problem. Your odds of triggering an avalanche on this layer are low, but the resulting slide would be large and destructive. 

    These avalanches are most likely in very steep, rocky, wind-affected terrain where more "trigger points" exist. Trigger points are locations where the overlying slab is thinner and the weight of you and-or your sled can more easily impact the weak layer. 

    ADDITIONAL DISCUSSION:Recent storms produced many natural and human-triggered avalanches on a layer of facets and surface hoar, now buried 1-2' deep. Recent observations indicate that this layer has gained strength. However, I wouldn't discount it just yet, particularly where it presents as a standing stripe of surface hoar. 

    (2/4/2021) These very large slab avalanches at the head of the Eagle Creek drainage likely released early in the morning on February 3rd. The largest slab in the foreground is over 1,000' wide. A very large avalanche is also visible in the background (West Fk Trail Creek). It appears to be at least 1,000' wide.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    A few inches of snow fell yesterday accompanied by moderate wind from the W. An additional 1-4" of new snow is possible today favoring the White Clouds. Be on the lookout for thin, freshly formed wind slabs. This problem is most likely at upper elevations with greater snow amounts that are exposed to stronger wind. 

    Wind speeds will be light for a good portion of today but will increase this afternoon. Remember that fresh slabs can form in a surprisingly short amount of time. Look for active wind-loading and cracking in the snow surface. Small wind slab avalanches (see video to right/above) can be great triggers for more deeply buried weak layers. Any avalanche that steps down to these persistent weak layers will be large and destructive.

Avalanche Discussion

Snowfall has returned to the northern and western portions of the forecast area as a series of Pacific storms impact the region through tomorrow. You can see our updated storm table here, or check out your favorite weather station here. Snowfall amounts in this zone total 2-4" in the White Clouds, near Galena Summit, and along the Smoky Crest. An additional 1-4" is expected in these areas today as well as another 3-6" tonight through tomorrow. All said and done, we're looking at up to a foot of new snow in these areas by Saturday afternoon.

This amount of snow and some wind will likely be enough to create avalanche problems on its own. Yesterday, Ben could hear the wind at upper elevations around Banner Summit and observers noted moderate to strong wind along the high peaks of the Smokys. Although we'll see a little lull in the wind today, it's forecast to increase as the next shot of snow arrives this afternoon. 

We've kept the danger elevated in this zone due to the concerning snowpack structure. The persistent weak layers here are well-developed and close enough to the surface to allow ample opportunity for human-triggering. Of all zones, this is the one I'd expect to behave the worst in the face of a big storm. So, although storm totals aren't expected to reach those of the Sawtooths and Banner, in the race toward instability, this zone has a head start. 

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