Lawinenlagebericht

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

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. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2

    Several weak layers are buried in the upper 1-2.5 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).  Wednesday, a wind slab released naturally south of Della Mountain, west of Hailey (photo here). Cracks shooting out from your machine or skis are clear indicators of an unstable slab. Small slabs that knock you off your feet and send you downslope can have 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. Any avalanche that fails on these deeply buried weak layers will be large and destructive. In the mountains above the Wood River Valley, the majority of the snowpack has faceted and triggering an avalanche on deeper weak layers is unlikely. 

    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.

Avalanche Discussion

A TALE OF TWO SNOWPACKS

Snowpack depths and characteristics are highly variable in this zone. In the mountains above the Wood River Valley, the snowpack has remained relatively thin. Cold temperatures and a lack of snowfall over the past month have produced a highly faceted snowpack. The older slabs that existed in the snowpack have largely lost strength and faceted away. If you're traveling in this portion of the zone you are most likely to encounter problems near the snow surface. Recent thin wind slabs will be small, but may be reactive thanks to the weak snow they are resting on. On very steep slopes (steeper than about 35 degrees) that are sheltered from the wind you will find a thick stack of facets at the snow surface. Loose snow avalanches involving these surface facets ("facet-lanches") will be possible to trigger today. These can pack quite a punch, thanks to the density of the faceted snow. A group of skiers on Carbonate near Hailey experienced this on Wednesday when a member of their party was caught in one of these slides. Fortunately, she was able to ski out of it before the snow puller her through a cliff band.

On the western side of this zone (Dollarhide area and west to the Soldiers) the snowpack is deeper. Slabs in the snowpack have retained their strength and triggering an avalanche involving buried weak layers remains a possibility. Strong winds in the past week have built a few rounds of stiff, hard slabs on top of the snowpack. These slabs present a hazard in themselves and are adding weight to the buried weak layers in the snowpack. You'll find much safer conditions, and better skiing and riding, in terrain that is sheltered from the effects of the wind. 

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. These types of slides are possible across this zone.

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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