Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanches continue to be human triggered on a daily basis.  Human triggered avalanches are expected again today. Areas where wind drifted snow has deposited as wind slabs are the most suspect. Persistent slab avalanches also remain a problem and could be surprisingly large when a failure occurs deep in the snowpack on old buried weak layers. CONSIDERABLE avalanche danger exists above treeline and near treeline. MODERATE avalanche danger continues below treeline.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Wind slab avalanches were triggered each of the last two days and this instability remains ongoing as blowing snow continues to drift and deposit onto leeward slopes. Wind slabs have become increasingly widespread over the last 24 hours. These wind slabs have formed mainly above treeline and near treeline on NW-N-NE-E-SE aspects, but maybe encountered anywhere wind drifted snow has deposited.

    Look for areas of blowing and drifting snow and identify where it has deposited as a wind slab.  This will be most prevalent on slopes adjacent to or below cornices and wind pillows. Move around these areas with an avoidance mindset.

    From yesterday, south of Carson Pass, CA.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Deeply buried weak layers are still an avalanche concern in the snowpack.  The most recent reported avalanche of this type was triggered Saturday on a NE aspect on the NE fringe of the forecast area. Unstable snowpit tests were identified yesterday on the eastern edge of the forecast area in Ophir Creek, NV. This particular avalanche problem is mainly an issue in areas where the snowpack was shallow prior to this last storm cycle such as along the eastern fringes of the forecast area. This includes portions of the Carson Range on the NE, E, and SE sides of Lake Tahoe and locations east of the Sierra Crest in the Luther Pass, Carson Pass, and Ebbetts Pass areas.

    This is a challenging avalanche problem to manage as signs of instability aside from avalanche activity do not often readily present themselves. Scale back terrain choices if you are traveling in an area with recent reported avalanche activity or any areas where the snowpack was shallow prior to the last storm cycle. The easy way to avoid this avalanche problem is by either avoiding NW-N-NE aspects and recreating on any of the other aspects or by utilizing only sub 30 degree angle slopes on NW-N-NE aspects without steeper terrain above or to the side.

    Avalanche the failed on old weak snow near the bottom of the snowpack on Saturday. Whites Creek Butte , NV.

Avalanche Discussion

* Wind slab avalanches were reported yesterday near Tragedy Springs (video) and Polaris Bowl (Carson Pass area) and on the N side of Castle Peak (Donner Summit area). Avalanche size ranged from D1 to D2.

* A slab avalanche of an uncertain weak layer type was skier triggered yesterday on a wind loaded portion of Waterhouse Peak (Luther Pass area) (link to report and photo).

* Evidence of widespread avalanche activity was reported from during the last storm cycle both above and below treeline in both upper and mid slope start zones on NW-N-NE-E aspects. Many filled in avalanche crowns with wide propagation consistent with persistent slab avalanches have been reported. 

Regions covered