Avalanche forecast

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Layers of weak snow are buried in the upper 1-3' of the snowpack and near the ground. Triggering an avalanche involving this weak snow is possible, particularly in steep, rocky terrain and during the heat of the day. Make your terrain selection accordingly and be alert to the consequences of being caught in a slide where you are traveling. You can significantly decrease your likelihood of triggering an avalanche by sticking to lower-angle terrain and exiting the mountains when the day heats up.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Over the weekend, the combination of new snow and wind built slabs in terrain where the wind blows. Continued wind transport was observed yesterday. These wind slabs are becoming less sensitive to the weight of a skier or rider, but some are sitting atop weak snow surfaces (facets and/or crusts) and remain touchy.  Recognize that wind-loading also adds stress to the weak layers buried in the snowpack (described in Problem 1 above). Any wind slab you trigger could step down to these deeper layers, producing a much larger, more dangerous avalanche. You are most likely to trigger a wind slab in steep, rocky terrain (photo at right). Even small slabs can have high consequences in this type of terrain.

    (3/1/2021) Natural wind slab in steep, rocky terrain at the head of Blind Canyon (near the head of Big Smoky Creek). NE aspect at 9,500'.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Warm temperatures and intense sunshine are causing significant settling in the upper portion of the snowpack. As we move into a period of climbing temperatures we focus our attention on our buried persistent weak layers. There are two broad categories:

    1. Weak layers that formed at the end of January and during the month of February are now buried 1-3' deep. These layers have produced avalanches across most of our forecast area in the past two weeks (Dollarhide, Galena Summit, Smiley Creek, Beaver Creek, Sawtooths, Banner Summit). The pattern of activity outlined by these avalanches points to these layers being most unstable on slopes that face the sun, where they are accompanied by crusts. Watch the video at right where Chris shows some of these layers in the White Clouds. Watch this video I took yesterday that shows how these layers looked near the crest of the Smoky Mountains.
    2. A pile of large-grained, weak snow (depth hoar) exists near the ground in this zone. You are more likely to trigger slides on the weak layers higher up in the snowpack, but any slide triggered on this deeply buried weak snow is likely to be unsurvivable.

    If I were to go and try to make an avalanche today I'd be looking in steep, rocky terrain where the snowpack is thinner and where it is being heated by the sun. As days pass without loading, the snowpack is getting some time to rest, which will gradually decrease the likelihood of triggering an avalanche on these weak layers. However, the possibility of triggering a slide here will be on the table for some time to come. If you choose to enter avalanche terrain, be alert that at least one of these weak layers almost certainly exists in the snowpack underneath you. Even as the danger decreases we still advise cautious and conservative terrain selection. Be alert to the consequence of being caught in a large avalanche in the terrain you are recreating in.

    ADDITIONAL DISCUSSION:Today's warm temperatures and bright sunshine are a perfect combination for loose snow avalanches. These sluffs can be dangerous on their own and may trigger larger slab avalanches as they travel downhill. Scott observed this exact combination yesterday in the Boulder Mountains (observation here, photo here). The heat is also affecting the large cornices that have formed throughout the season. These beasts sag during the heat of the day, eventually tumbling off the ridges they are attached to. This makes for a "great" trigger for the persistent weak layers described above.

Avalanche Discussion

PERSISTENT WEAK LAYERS AND DECISION MAKING

Everything is much easier at the far ends of the danger scale. When conditions are either clearly stable or clearly unstable it is quite simple to make decisions in the mountains. In the gray area in between safe and dangerous things get tricky very quickly. When we add persistent weak layers (PWL) into the mix this trickiness is multiplied. And that's exactly where we are now.

As stability gradually improves and the likelihood of triggering avalanches gradually decreases, I find myself drawn towards avalanche terrain. After all, I became an avalanche forecaster because I truly love spending my time in steep, snow-covered mountains. But only when I can do so safely. As I think about the terrain that I might be able to safely enter on any given day, the presence of PWLs in the snowpack significantly limits the terrain that is available. In order to feel comfortable that a given slope is reasonably safe to play on, I have to be able to prove to myself that the PWLs are either absent or entirely unreactive. For each slope, I re-create the seasonal weather history that formed the different PWLs, think about the loading events that have stressed these layers and the patterns of natural avalanche activity that those loading events have caused.

If that all sounds complex then I think I am doing a good job of describing the process. However, the complexity doesn't end there. At the moment, we find ourselves in a gradual warming trend, with each day slightly warmer than the last. Those warming temperatures are causing wet snow issues in the upper snowpack and adding stress to buried weak layers as the snowpack creeps downhill. So, in addition to the PWL problems we are seeing a diurnal pattern of fluctuating hazard overprinted on top. At the Sawtooth Avalanche Center, we forecast for an area of over 3,000' square miles. Within that area, I can think of very few pieces of avalanche terrain that I would confidently enter right now. Is that frustrating and unsatisfying? Absolutely. But trust me, I'm right there in the same boat with you.

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