Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
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Lawinengefahr

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

Kernpunkte

Large avalanches, 1-4 feet thick, are most likely to be triggered in areas where wind has formed drifts or stiffened the snow surface. In areas sheltered from the wind, avalanches are less likely, but they’re still possible. You could trigger avalanches remotely—from flat terrain below, above, and to the sides of steep slopes.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    What and where is it: You could trigger 1.5-4 foot thick slabs, especially where wind formed drifts or stiffened the snow surface. Triggering an avalanche is less likely—but not out of the question—on steep slopes that are completely sheltered from the wind. The slabs rest above a variety of weak layers (facets, surface hoar, crusts, and combinations). The widespread nature of these weak layers means avalanches are possible on many aspects. 

    How can you recognize it: Snowpack cracking, and collapsing or whumpfing, are clear signs of unstable conditions. Watch for snow pillows, dunes, and ripples, and feel for stiff snow under your feet or sled. These are signs the wind has been at work transporting snow. Persistent Slabs won't always present with obvious signs of instability, assume the weak layers exist on most slopes.

    How can you manage it: By avoiding steep, wind-loaded slopes, you can significantly reduce your chances of triggering an avalanche. Persistent Slabs can release in surprising ways, break wider than expected, and release above or hundreds of feet away from where they are triggered. Remotely triggering an avalanche from flat terrain near steep slopes is a real possibility. Keep a close eye on your partner and the terrain that's above you. Manage your group by riding or crossing steep slopes one at a time, and avoid areas where terrain features like gullies, cliffs, or dense trees could increase the consequences of even a small slide.

    Additional Discussion: You may be able to trigger wind slab avalanches that have formed near ridgelines and in cross-loaded areas on the sides of gullies. The size and chance of triggering these slides increase significantly as you climb into windier, alpine terrain at upper elevations. These avalanches could step down to the buried weak layers described above.

    (12/29/2024) This persistent slab avalanche was remotely triggered from gentle terrain above the crown. NW slope near 8600' in the Prairie Ck drainage of the Smoky Mtns. 

    Photo: Jon Preuss

Avalanche Discussion

Don’t let sunny skies fool you into a false sense of stability today. The recent storm deposited 2–3 feet of snow (2–3 inches of snow water equivalent) in this zone, and the snowpack will need time to adjust to the added weight. In the past few days, numerous natural and human-triggered avalanches have been reported across the forecast area:

These are just a few key observations. For more, visit the Observations Page.

Although the loading has stopped, recent reports of both natural and human-triggered avalanches make us wary of entering avalanche terrain. In the Banner Summit zone, the deeper snowpack may make it harder to collapse slopes or trigger avalanches. However, due to the limited number of recent observations, some uncertainty remains.

Assume that weak layers are present on most slopes. It's often said that weak layers are guilty until proven innocent, and recent observations show that mid-December weak layers are still proving to be a concern. Hedge your bets by skiing or riding slopes one at a time, and seeking non-wind loaded slopes. Choosing to ride in non-avalanche terrain is an appropriate way to manage today's avalanche problems. 

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