Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Dangerous avalanche conditions exist and triggering a large avalanche remains likely on many slopes. Avalanches will fail on a layer of weak snow that is buried 2-3 feet below the snow surface. You can reduce your risk of encountering such a slide by sticking to lower-angled terrain that is not threatened by steeper slopes above. Avalanches may be triggered remotely—from below, above, and to the sides of steep slopes. 

Problemi valanghivi

  • Persistent Slabs

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

    Weak snow is buried beneath a 1.5-2.5' thick slab of snow in this zone. This layer of weak snow exists across our Forecast Area and has been the culprit in almost all of the avalanches we've observed in our region this season. In the past six weeks we've recorded nearly 400 avalanches—the vast majority broke on this persistent weak layer. Around 20 of these were human-caused. 

    Even though we are a week out from a major loading event the snowpack is continuing to give us clear evidence of instability, here is a quick look at some of the red flags from this weekend:

    • Riders in the White Clouds on Sunday experienced shooting cracks that shattered entire slopes.
    • Chris was in the Pole Creek drainage on Sunday and found an unstable snowpack structure and his snowpack tests returned unstable scores (video at right/above).
    • I was in the Owl Creek drainage on Sunday and found a similar snowpack, experienced cracking and collapsing, and got unstable snowpack test scores in my pit.
    • Numerous observers on Galena Summit continue to report unstable snowpack test scores.

    Well, why aren't people out there triggering avalanches then? Put simply, it is because most folks have been avoiding avalanche terrain. If you go out in this zone today, I'd recommend you continue this pattern. These ongoing signs of instability make it clear that the odds of triggering a slide are not decreasing significantly. You can reduce your chance of being caught in an avalanche by avoiding slopes over about 35 degrees, especially those that have been affected by the wind. Given the possibility of remote-triggering slides, avoid terrain with steep slopes above you. 

Avalanche Discussion

I've never returned home from a day of skiing or riding and thought to myself, "I'm satisfied, I never need to go into the backcountry again." Truth be told, every day I spend in the snow-covered mountains just leaves me looking forward to the next one! In order to ensure a long future filled with snowy summits, I know that I have to behave in accordance with the dictates of the snowpack. We don't make the rules, she does.

Fortunately, every season the snowpack provides us great opportunities to learn. In fact, the years with the worst stability (like this one) are usually the ones where we are offered the most learning opportunities. Even though conditions have been quite dangerous this year, the snowpack is relatively simple: weak, early season snow is buried beneath a 1-3+ foot thick slab of snow. As you travel around different areas in our region I'd recommend pulling out your shovel, digging a pit, and seeing if you can identify these layers. This simple set-up gives us a great natural laboratory for learning about the properties of slabs, weak layers, and the interplay between them. I'll spend a little time talking about slabs today, stay tuned for some insight into weak layers in tomorrow's discussion.

SLABS: The primary driver that is creating variable Avalanche Danger across our forecast area is the nature of the slab on top of the weak snow. Let's take a quick tour through our snowpacks, from thickest to thinnest:

  • Where the snowpack is deepest (Banner Summit Zone), this slab is 3+ feet thick and very dense. When you are digging here, expect to be digging a big hole through dense snow. This meaty slab makes it difficult to impact the weak snow below it, but also makes it so any resulting avalanche would be very large and destructive.
  • Traveling south from Banner into the White Clouds, the mountains above Smiley Creek, and the mountains around the headwaters of the Big Wood River you will find a 1.5-2.5 foot thick slab that isn't nearly as dense as the slab around Banner. This set up is where you are most likely to trigger an avalanche today. The slab is still plenty strong to be "communicating" fractures, but it isn't so strong that it is difficult to impact the weak layer.
  • As you continue south, into the mountains above the Wood River Valley and north of Carey in the Little Wood drainage, you will encounter areas where the total depth of the snowpack is less than 2 feet. In most of these areas the slab just isn't thick or strong enough to be causing widespread problems...yet. A notable exception to this is in areas where the wind has thickened the slab that rests on top of the weak snow beneath. 

Looking for a quick recap of what happened last week? Be sure to check out our latest edition of the Weekend Update, my man Chris will fill you in!

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