Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The combination of new snow and wind is building 1 foot thick slabs of wind-drifted snow. You are most likely to trigger an avalanche in terrain that has been affected by recent winds. There is a small chance that slides could break into buried weak layers, producing a more dangerous avalanche.

Problemi valanghivi

  • Wind Slabs

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

    Today's storm will bring 2-5" of new snow and a good dose of wind to this zone. This combination is building slabs that will be sensitive to your weight today. You are most likely to find these slabs in upper elevation terrain but they may extend down into middle elevation terrain as well, thanks to the strength of the wind. Similar slabs formed during a storm on Sunday. Today's snow will make these older slabs more difficult to identify visually, but they may still be reactive.

    Expect to find these slabs along ridgelines and adjacent to cross-loaded terrain features. Look for signs that the wind has been at work and avoid these areas. Pillows and dunes of snow are a great indicator of this. If you are traveling through the terrain here and you find that the snow depth is increasing or that the new snow is becoming denser you've likely found a wind slab. Cracking in these fresh drifts are clear signs of instability. Many of these slabs will be on the smaller side, but in the right terrain, some may be large enough to bury you. I was traveling in this zone yesterday on Horton Peak, where I found a new layer of surface hoar on upper elevation slopes. This layer is about to be buried and may make today's slabs a bit touchier.

    In addition to the surface hoar I just mentioned, several weak layers exist in the upper 1-2' of the snowpack. These layers formed during the dry periods between storms over the past two months. Avalanches that fail on these weak layers are much less likely than a typical wind slab, but would be larger and more destructive. You can significantly reduce the likelihood of encountering a slide that breaks on these weak layers by avoiding very steep terrain that has been affected by the wind (steeper than about 35 degrees). Read more about these weak layers in the Forecast Discussion below. 

    (3/11/2022) A heli-ski guide triggered this small wind slab on Friday while stomping cornices along a ridge. It broke 12" thick and 100' wide, running on a slick crust. Western Smokys, 9000', E aspect. Photo: Sun Valley Heli Ski

Avalanche Discussion

UPPER SNOWPACK COMPLEXITY

It has been a dry few months in our neck of the woods. Small storms have helped to break up this extended drought but have left us with a complexly-layered upper snowpack. The dry periods between storms allowed for a range of weak layers to form and these layers were subsequently buried by the next storm. With each new layer, the character varies significantly as you climb in elevation and wrap around to different aspects. This pattern has been repeated at least half a dozen times in the past 6 weeks. Sound complex? Perfect, I'm doing a good job painting the picture. Read on.

On slopes that face the sun, these weak layers are generally in the form of crusts with associated facets. On slopes that face away from the sun you'll find facets and surface hoar buried at many of these intervals. On the margins between sunny and shady aspects you will find all of these things. A warm storm at the beginning of March brought rain that fell above 9,000' in many areas, adding another weak layer to the mix. Thanks to the variability of these weak layers, assessing the slope-scale presence and stability of any one of these layers is challenging at best, and borderline impossible at worst.

So how do you deal with a problem like this? Well, the answer isn't a terribly satisfying one. The only way to guarantee these layers won't be an issue is to avoid the terrain where they exist. Unfortunately, that describes just about every slope out there. Fortunately, you can significantly reduce your exposure to the hazard posed by these weak layers by choosing gentler sheltered terrain. You're most likely to trigger a slide involving this weak snow on very steep slopes (steeper than about 35 degrees) where the wind has built slabs in recent days and weeks. 

Frustrating? Yes, no doubt about it. Don't worry, I'm right there with you. One of my favorite things to do is to ski in avalanche terrain. I spend hundreds of days each year with skis on my feet. When I can do it safely my preference is to be in steep avalanche terrain. But, my priority is always to come home in one piece at the end of the day. Because of the uncertainty associated with these weak layers, I've taken a step back from steep slopes where these weak layers exist, particularly in places that just had a bunch of snow piled up on top of them. There is lots of good skiing and riding to be found in gentler terrain that hasn't been affected by the wind. It may not be my first choice for this time of year, but it's the only way I can ensure I can head back out again tomorrow.

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