Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Hochgebirge
1 · Gering
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 13 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

MODERATE avalanche danger will continue on the near and below treeline NW-N-NE aspects on slopes 32 degrees and steeper due to lingering persistent slabs.

Human triggered avalanches remain possible. Due to the shallow snowpack any avalanches that do occur would drag people through and into obstacles like rocks, stumps, and other hard immobile obstacles.

Lawinenprobleme

  • Deep Persistent Slabs

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

    Persistent slabs remain widespread on the near and below treeline NW-N-NE aspects. The Dec. 7th facets represent the persistent weak layer. The layer of cohesive snow above them represents the slab layer. This combination remains unstable on the edge of failure waiting for some kind of trigger to break it. Human triggered avalanche activity remains possible on these slopes. People can trigger these kind of persistent slabs remotely while standing in low angle terrain or on ridgelines or anywhere that the snowpack under their feet connects to steeper and/or deeper terrain because fractures can travel through the persistent weak layer. 

    Any of these avalanches that do occur would drag a person through rocks, stumps, trees, and other obstacles because of the shallow snowpack and the fact that the near and below treeline terrain holds the most unstable snow as well as the greatest number of obstacles.

Avalanche Discussion

Yesterday observations in Deep Creek (video, photo, snowpit) and in the Wild Card (more info) area (Mt. Rose backcountry) showed a snowpack structure with a layer of well-consolidated snow sitting above a layer of weak sugary snow (Dec. 7th facets). In both of these areas snowpit data and tests indicated that the snowpack remains weak and that if it does break, the resulting fracture can travel along the persistent weak layer. In the Deep Creek area observations showed small improvements in the snowpack since 12/14 and no human triggered collapsing or whumpfing occurred. On the other hand, the additional weight of people on the snowpack in the Wildcard area triggered large whumpfs and collapses.

The meager amount of new snow that fell yesterday did little to change the state of the snowpack. No new wind slabs formed in either of these areas yesterday due to the lack of new snow combined with the fact that the strong winds remained limited to ridge crests above treeline.

Barely covered rocks, stumps, logs, and other hard, immobile, season-ending, equipment-breaking objects still exist on all slopes. The shallow snowpack does not have enough structure or strength to keep a person above all these things. It only camouflages their existence.

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