Bollettino valanghe

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Mon
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

Triggering a 1-2 foot thick avalanche in wind-loaded terrain remains possible. Avalanches failing on deeper weak layers are less likely but can't be ruled out in rocky, wind-affected terrain. You can significantly reduce your risk by steering clear of slopes steeper than about 35 degrees.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Several weak layers are buried in the upper 1-2 feet of the snowpack. On slopes that face away from the sun, you'll find some surface hoar and facets at these interfaces. On slopes that face the sun, you'll find crusts with some small facets here. Moderate to strong winds this week created a batch of stiff wind drifts in terrain exposed to the wind, building slabs on top of these buried weak layers. Thursday, skiers on Titus Ridge found this combination of unstable slab+weak layer when they remotely triggered a small wind slab from 50 feet away (photo here).  Cracks shooting out from your machine or skis are clear indicators of an unstable slab. Even small slabs that knock you off your feet and send you downslope can carry high consequences in the wrong terrain.

    Further down in the snowpack, you'll find layers of weak snow near the ground. Triggering an avalanche on these layers is most likely in wind-affected alpine terrain where scouring has produced thinner areas of the snowpack (watch Ethan's video at right/above). Here, you'll have better access to this weak snow, and triggering a slide involving it remains a concerning possibility. I skied in the Boulder and the Pioneers this week and the presence of this weak snow dictated the terrain that I was comfortable entering. Any avalanche that fails on these deeply buried weak layers will be large and destructive.

    Avalanches failing on persistent weak layers can break well above you on the slope and may break wider than you expect. You can significantly reduce your risk by steering clear of wind-affected, rocky, alpine terrain steeper than about 35 degrees.

    ADDITIONAL DISCUSSION: Small loose snow avalanches will become possible as the sun warms up the snow surface and melts existing crusts. Pay attention to the snow you are traveling through and look for roller balls and pinwheels as indicators that the surface snow is heating up. These slides start small but may pick up speed and snow quickly as they travel downslope. The steep, rocky terrain of the Pioneers, Boulders, and White Clouds is great at producing these types of slides.

Avalanche Discussion

STAYING OUT OF TROUBLE

As we get further out from snowfall we are seeing the likelihood of triggering slides gradually decreasing. As a result, many of us find ourselves drawn to larger, more complex avalanche terrain. In this terrain, the result of being wrong in your stability assessment can carry high consequences. Sometimes the best way to avoid getting in trouble in the mountains is by knowing what might get you into trouble in the first place. There are two broad scenarios that you should be on the lookout for today in this zone, read on:

Slabs+Weak Layers: After a strong start to the season, snowfall in January largely missed this zone. Because of that, the snowpack has remained thinner here and the weak layers we buried in November, December, and January are all still "in play". Slides on weak layers that are closer to the surface are more likely, but large avalanches failing on weak snow deeper in the snowpack can't be ruled out. You're most likely to get into trouble in places where stiff wind slabs and drifts are resting on a weak, faceted snowpack in rocky, wind-affected, alpine terrain. There is a lot of terrain that looks like this in the Pioneer, Boulder, and White Cloud Mountains, which make up the majority of this zone.

Loose Snow: Temperatures in the mountains remained in the 20s F last night and are already slowly climbing in the pre-dawn hours this morning. Today will be mostly clear and winds will remain light. As the February sun heats up the snow surface, loose snow avalanches will become possible. We've seen a few rounds of these failing naturally in the past few days. Monitor the snow surface as the day heats up and be ready to move to a colder, shadier aspect as it becomes moist.

Enjoy the beautiful weather and the gradually improving stability, but remember that we aren't out of the proverbial woods yet. If you are stepping out into bigger, more complex avalanche terrain you'll be well served to  think about the consequences of being caught and carried in the terrain you've chosen.

For more info on what happened last week check out Scott's latest Weekend Update.

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