Lawinenlagebericht

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

You could trigger avalanches large enough to bury you on slopes with old, weak snow at the base of the snowpack (upper elevation slopes and shaded middle-elevation slopes facing W-N-E). Avalanches can be triggered by the first, third, or tenth rider on a slope, and may break well above you. Pockets of recently wind-drifted snow will be small but may be easy to trigger.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    You can trigger large avalanches involving dense, 1.5-2.5 foot thick slabs that fail on weak, early-season snow. You'll find this unstable combination on all upper elevation slopes and on middle elevation slopes that face away from the sun (W-N-E). On shaded slopes, a thick stack of facets sits underneath this slab. On slopes that face the sun, you'll find a thin, less obvious layer of facets on top of a crust. 

    As days pass without significant loading, obvious signs of instability such as collapsing of the snowpack have decreased. Don't interpret this as an indication that the problem has gone away. The first sign of instability involving this weak snow may be the large slab avalanche you and your friends trigger. Tracks on a slope are not indicators of stability — avalanches can be triggered by the first, third, or tenth rider on a slope, and may break well above you. 

    ADDITIONAL DISCUSSION:  A minor storm brought 3-5 inches of snow early yesterday morning. Moderate, gusty N winds pushed this snow around in exposed terrain, building small slabs that remain reactive to your weight today. In the steep terrain of the Sawtooths, slabs also commonly form on the aprons below cliffs and couloirs. These will be small, but can knock you off your feet and run downslope quickly thanks to the stiff surfaces underneath.  Small loose snow avalanches involving this new snow will be easy to trigger on steep slopes. Small avalanches can be effective triggers for slabs failing on the weak snow near the ground. 

Avalanche Discussion

Lingering persistent slab instabilities are both challenging and frustrating to deal with. They test our patience and our imagination. As time stretches on since the last major loading event, the obvious signs of instability that the snowpack gives us decrease. The evidence of previous natural avalanche activity has been masked by recent, small storms. While you might be forgiven for letting the presence of weak snow at the base of the snowpack slip from your mind, the large avalanches that fail on this weak snow will not be forgiving. 

You'll head out into a beautiful, cold, snowy world today. Pay attention to the minor instabilities involving yesterday's snowfall — small, sensitive wind slabs and small, easy-to-trigger loose snow avalanches. These issues will be easy to identify, and are unlikely to produce large avalanches on their own. But don't get distracted. The weak base of our snowpack should continue to be your primary concern. In this zone, a very dense, 1.5-2.5 foot thick slab is resting on top of these facets. This makes it more difficult to impact the weak snow underneath but also means that any triggered slides will be large and destructive. You're most likely to trigger these avalanches on steep, wind affected slopes where the overlying slab has thin spots that make it easier to impact the weak layer. 

Entering avalanche terrain is a choice we make. When we do so, we accept the potential outcomes of our choices. Triggering large, destructive avalanches remains an uncomfortable possibility today. The really hard part about this is that the flip side of the coin is also true — there is a possibility that you don't trigger an avalanche on the slope you choose to ski or ride. The important thing to keep in mind is that regardless of the outcome, you are entering a dangerous lottery on slopes with old, weak snow at the base of the snowpack. There are very few places in our forecast area where I'm even entertaining the idea of playing this game. 

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