Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Wed
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Another strong winter storm will bring gale-force winds and heavy snow to the region today.  Expect widespread avalanche activity. Any slope steep enough for snow to avalanche on will be suspect today. Travel in, near, or below avalanche terrain is not recommended.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    More snow and strong winds today will continue to pile wind-blown snow on top of the wind slabs that have formed over the last few days. Wind slabs will become more significant and more extensive today. They should also be easier to trigger. Expect large natural wind slab avalanches to occur today. Human-triggered wind slab avalanches are very likely If a person ventures too close to a wind-loaded slope. NW-N-NE-E-SE aspects in near and above treeline terrain will hold the largest and most fragile wind slabs, but some of them may also exist below treeline due to the strength of the winds. Wind slab avalanches could be very large today and could run down into below-treeline terrain and areas of mature timber.

    Traveling in, near, or below avalanche terrain is not recommended. Blowing snow and poor visibility will make seeing and identifying avalanche terrain harder today.

    (1/9/2023)

    Skier triggered D1 R5 wind slab avalanche - Near treeline - NE facing.

    Photo: Brandon Schwartz

  • Storm Slabs

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

    Today's storm snow will pile up too fast to bond to the snow below or to itself. Traveling on a steep slope could easily trigger a storm slab avalanche today. In addition to the weaknesses that form during today's storm, some of yesterday's storm slabs may remain unstable. Slabs of unstable storm snow could exist on any aspect on slopes sheltered from the wind.

    If attempting to navigate in low-angle, non-avalanche terrain in wind-protected areas below treeline today, take great care not to wander into areas with steeper avalanche terrain above. Natural avalanches from above could easily travel down into lower-angle terrain today and into treed areas.

    (1/9/2023)

    Instability within new storm snow under wet heavy surface snow on Powderhouse Peak.

    Photo: Jason Bilek

  • Persistent Slabs

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

    Faceting along the thin Jan 4 rain crust and unstable snowpit test results have been reported from NW-N-NE aspects in the 7,500' to 8,500' elevation range in the Border Ruffian and Blue Lakes areas south of Carson Pass. The first avalanche on this layer may have occurred on 1/8. Observations targeting this layer at various elevations in the Independence Lake, Donner Summit, Pole Creek, Mount Rose, and West Shore Tahoe zones have not revealed any faceting or weakness on this specific layer. Substantial unknowns remain regarding the areas where this layer is weak and problematic.

    In areas where this layer is weak and problematic, it is currently receiving stress from the loading during these storms. An avalanche that fails on this crust/facet layer would fail at a minimum of 2 to 3 feet deep in the snowpack, likely have wide propagation, and could be triggered from low on a slope or the side. Traveling in, near, or below avalanche terrain is not recommended.

    (1/8/2023)

    Natural avalanche in Polaris Bowl on The Nipple, south of Carson Pass, CA. This avalanche occurred during a period of intense wind loading. Unconfirmed, but based on the wide propagation and areas of jagged crown, this may have been a persistent slab avalanche failing on the Jan 4 crust/facet layer.

    Photo: Public

Avalanche Discussion

Recent Observations

  • More avalanche activity was reported yesterday, including wind slab avalanches on NE-E aspects in near and above treeline terrain, storm slab avalanches on N-NE aspects, and wet loose avalanches on all aspects at lower elevations. They ranged in size, but some involved more than enough snow to bury or injure a person.
  • A very large avalanche (D2.5) that may have failed on the facets around the Jan 4 rain crust occurred naturally on 1/8 during intense wind loading in Polaris Bowl on The Nipple, south of Carson Pass.

Regions covered