Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
Veraltet — dieser Lagebericht ist 12 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Human triggered avalanches remain possible today. Above 8,000 ft, MODERATE avalanche danger exists on all aspects on slopes 35 degrees and steeper due to the presence of dense wind slabs, storm slabs, and wet snow. If the dense slabs do break, they could break above the person who triggers them and result in avalanches large enough to bury a person. Don't let the new snow lead to careless decision making.

Lawinenprobleme

  • Wind Slabs

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

    Additional snow accompanied by strong SW winds should have created more wind slabs on wind loaded and cross loaded NW-N-NE-E-SE aspects. The largest of these wind slabs will exist above 8500 ft. in near and above treeline terrain where more new snow has accumulated. In these areas wind slabs could measure more than 3 to 4 ft. in depth. The new wind slabs have formed above previous wind slabs. On northerly aspects some of these now large wind slabs sit on top of old crusts that have a layer of softer snow below them. Some wind slabs could still linger in isolated areas in below treeline terrain or in more sheltered areas due to the strong winds during this series of storms.

    Human triggered avalanches involving these winds slabs remains possible. These dense and hard wind slabs can break above the person who triggers them or could be triggered by the 2nd, 3rd, 4th, or nth person on the slope. Typical obvious clues of instability and other tests may not provide reliable data as to whether or not these wind slabs will break. Wind loaded slopes steeper than 35 degrees above 8500 ft, represent the most likely places to find unstable wind slabs. Wind loaded slopes 38 degrees and steeper, couliors, unsupported slopes above cliffs, or slopes in complex or extreme terrain could be especially problematic today. Some of these slabs could fail on or just below the old snow surfaces and could propagate along those old snow layers.

  • Loose Dry

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

    Since yesterday's snowfall started off with a short period of slightly colder snow and then warmed up, a layer of softer new snow may still exist below the heavier new snow that fell later in the storm. This upside down storm snow layering means that some unstable storm slabs may exist in wind protected areas above 8,500 ft. Human triggered storm slab avalanches will be possible on slopes steeper than 35 degrees today in wind protected areas in both near and below treeline terrain. Due to the wet snow that exists in many areas some of these storm slabs may have wet snow characteristics as well. If these do fail, they should mostly just involve the new snow, but it is not impossible that some of these slabs could fail on or just below the old snow surfaces on some steep northerly aspects above 9000 ft.

  • Loose Wet

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

    Even though temperatures have gotten colder, wet snow will still remain just below the surface on all aspects below 8500 ft. due to the copious amounts of rain that have fallen over the last several days. It will take some time for this wet snow to refreeze, and some loose wet snow instabilities will remain possible until the snow does refreeze.

Avalanche Discussion

Yesterday on Tamarack Peak, 17 to 21 in. of dense recent snow existed above the old crusts with a layer of softer snow around the crusts in some areas on N-NE aspects. Snowpit tests targeting this layer on N-NE facing slopes between 9200 ft. and the summit of Tamarack (9875 ft.) indicated that it would be difficult to trigger a fracture in this softer layer below the new snow, but that if a fracture did start it may be able to travel through the layer. Some snowpit tests targeting the same layer near Carson Pass showed unstable results while other nearby tests showed stable results. Above these older snow layers, observations in both locations indicated that the new dense snow continues to consolidate. As temperatures warmed up during the afternoon, rain started falling on the snow up to at least 8800 ft. in both areas. On steep north facing slopes on Chickadee Ridge several roller balls started to occur as the day warmed up.

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