Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Hochgebirge
1 · Gering
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 11 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The avalanche danger has decreased to LOW for all elevations and aspects. LOW avalanche danger means that while avalanche activity may be unlikely, it is not impossible. Unstable snow in the form of small isolated wind slabs or persistent slabs could still exist on isolated terrain features especially in complex or extreme terrain.

Lawinenprobleme

  • Deep Persistent Slabs

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

    Triggering a persistent slab avalanche has become unlikely. Data from around the forecast area indicates that the persistent weak layers present in the snowpack have adjusted to the load above them and that if they do break the resulting fractures would not travel very far along those buries layers. However, some variability and uncertainty surrounds persistent weak layers and persistent slab avalanches. If the right trigger found the right spot on a slope where a persistent weak layer exists around one of the buried rain crusts, a human triggered persistent slab avalanche is not impossible today. Large triggers like multiple people on a slope or large cornice failures would have better chances of triggering an unlikely but not impossible persistent slab.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1

    The wind slabs that linger on many aspects above treeline have grown difficult to trigger since they have bonded to the snowack below them in most areas. Even though avalanches involving these wind slabs have become unlikely, some unstable wind slabs may still linger on isolated, steep, wind-loaded terrain features like couliors, unsupported wind-loaded slopes above cliff bands, or other complex/extreme terrain.

Avalanche Discussion

Yesterday, observations from around the forecast area indicated a trend of settlement and consolidation in the snowpack. Snowpit tests and data from Rubicon (on the West Shore), Trestle Peak (near Donner Summit), Tamarack Peak (Mt. Rose backcountry), and Indian Valley (between Ebbetts Pass and Carson Pass) did not reveal any obvious signs of instability. Some of the data did indicate that the snow around the 12/13 rain crust has the potential to pose future problems when additional snow load arrives. In all of these areas the NE winds had scoured much of the recent snow away from the upper-elevation, exposed, N-NE-E aspects leaving behind firm wind pack surfaces and exposed crusts. On the more sheltered N-NE-E aspects the surface snow remained cold and soft. Observers also reported that sunshine and warm temperatures allowed some wet surface snow to form on sun-exposed southerly aspects by yesterday afternoon. Ski cuts in the Tamarack Peak area and snowmobile cuts in the Indian Valley area on some wind loaded test slopes caused some very small dinner-plate size cracking in small, shallow, isolated, and inconsequential wind slabs.  

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