Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

On the heels of another period of HIGH avalanche danger last night, CONSIDERABLE avalanche danger will exist today near and above treeline on all aspects on slopes 35 degrees and steeper due to ongoing wind slab formation. In wind protected areas below treeline, MODERATE avalanche danger exists on slopes 35 degrees and steeper due to potential storm slabs. Large human triggered avalanches remain likely today. Natural avalanches are possible.

Lawinenprobleme

  • Wind Slabs

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

    Ongoing gale force SW winds this morning will continue to transport snow and build problematic wind slabs in near and above treeline areas. In some cases wind slabs may exist below treeline as well. The vast majority of wind slabs are expected on wind loaded NW-N-NE-E-SE aspects. Wind slabs may exist on S-SW-W aspects, especially after winds shift to the NW this afternoon and change the pattern of distribution. Human triggered avalanches are likely today and large avalanches could occur. In the areas of direct wind loading, natural avalanches remain possible.

    Identify and avoid steep wind loaded slopes. Use clues such as recent avalanche activity, blowing snow, cornice formation, wind pillows, and snow surface patterning to determine where wind loading is actively occurring or has occurred recently.

  • Loose Dry

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

    In wind protected areas below treeline, human triggered storm slabs are possible today. Short lived weak layers within the new snow from last night may remain reactive during the day today. Clues such as recent avalanche activity and cracking in wind protected areas are obvious indications of storm slab instability. Keep in mind that treed areas can protect from the wind and wind related avalanche problems but not from storm slabs. Seek out lower angle (sub 30 degree) slopes without steeper terrain above when signs of instability are present.

Avalanche Discussion

Observations made and received yesterday from Powderhouse Peak (Luther Pass area), Hidden Peak (West Shore Tahoe area), Tamarack Peak (Mount Rose area), and Andesite Peak (Donner Summit area) found a wide range of snowpack instability. Evidence of instability ranged from natural and human triggered wind slab avalanches to signs of instability limited to the presence of recent new snow and blowing snow. On Hidden Peak, the signs of a natural wind slab avalanche were observed along the summit ridge, with widespread skier triggered cracking noted in wind loaded areas near treeline within the top 300' to 400' of the peak. Similar conditions were observed on Powderhouse Peak with an intentionally snowboarder triggered wind slab on a small test slope. A trailhead report of a skier triggered avalanche involving 1 to 2 people in the Fireplug area near Tamarack Peak was received, but details are few. A second report of a very small skier triggered wind slab was also received from the Fireplug area. See below for more info, video, and photos.

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