Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 7 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You’re most likely to trigger a slab avalanche where wind and recent snow has combined to form fresh drifts. While less likely, it’s possible to trigger an avalanche on older weak layers buried 1-3 feet deep. These layers are widespread at middle and upper elevations and the resulting slide will be large enough to bury you. A powerful storm will increase the danger overnight and into the weekend.

Problemi valanghivi

  • Persistent Slabs

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

    While this zone has received less snow (both recently and throughout the season) than its neighbors to the north, it boasts similar widespread weak layers near the middle and base of the snowpack. Triggering an avalanche on these layers remains a possibility, especially in areas with stiff wind-blown snow at the surface (see video).

    An avalanche failing on one of these layers has the potential to break wider than expected, span multiple terrain features, and will include the majority of the snowpack. Slides may be triggered from a distance and have the potential to pull back into low-angle terrain near the top of a slope. 

    It’s a safe bet to assume one or more persistent weak layers sit beneath your boards or sled. To reduce my chances of triggering a slide I’ve been steering clear of obviously wind-loaded terrain and sticking to gentler, lower angle slopes. 

    Additional DiscussionIn exposed upper elevation terrain, expect to encounter fresh drifts and wind slabs–especially in the Soldiers and near Dollarhide Summit. These drifts can be particularly touchy where they lie above slick, hard, wind-buffed surfaces or the persistent weak layers described above. Fortunately, the drifting should be easy to spot and avoid.

Avalanche Discussion

Well, here we are again. If you’ve been around Central Idaho (or more generally the Intermountain West) long you’ve come to expect these stretches when we deal with persistent weak layers that linger for weeks or even months at a time. As a forecaster, it's a tough situation to be in. It’s much easier for us to tell you when it’s generally safe, or the opposite, when the mountains are coming crashing down. On average, however, we often bounce around in this middle ground where triggering a destructive avalanche isn’t likely but the possibility is certainly on the table. 

Our two primary weak layers are buried near the middle and base of the snowpack; surface hoar (or crust + facets in some areas) and depth hoar, crusts and facets near the ground. A recent Instagram comment asked how and when we can expect these weak layers to finally go away? In a nutshell, weak layers that are more deeply buried will tend to gain strength, in part due to the weight of the overlying slab and part due to the low temperature gradients that encourage rounding. In some areas, where these weak layers are buried 2-3’ deep, snowpack test scores have pointed to these layers gaining strength, but we’re not out of the woods yet. In shallower areas, we’re still experiencing collapsing, and these weak layers have improved very little.

Hopefully, we’ll have a larger body of evidence to pull from after the upcoming series of storms. I say “hopefully” because there’s an overarching “well, I guess we’ll wait and see” mentality to our conversations leading up to this storm. It’ll be interesting to see what slides and what doesn't, of course, a lot of this activity is tied to how much snow we get, where it falls, and how fast. Given the spatial variability of the current snow depths, slab properties, and weak layers, the outcomes may vary drastically over a short distance. While these weak layers are put to the test, take a big step back and record what you see—the next several days should be interesting.

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