Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Ongoing gale force winds combined with new snow will continue to create areas of blowing and drifting snow near ridgetops. This drifting snow will continue to deposit as unstable slabs of wind drifted snow in lee areas. Consider avoiding slopes below cornice features along with other areas where wind blown snow is depositing.

Avalanche problems

  • Wind Slabs

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

    Intense blowing snow and wind slab avalanches were reported yesterday. Ongoing winds today combined with new snowfall will continue to blow and drift substantial amounts of snow. Wind slabs will continue to form in lee areas near ridgelines today mainly near treeline and above treeline on NW-N-NE-E-SE aspects. Wind slabs may also form to a lesser extent in below treeline areas due to the strength of the winds.  Wind slab avalanches are expected to be large to very large in size today. Natural avalanches are possible, human triggered avalanches are likely.

    Use blowing snow, wind drifted pillows of snow, cornices above a slope, and wind textured snow surfaces as clues to indicate where unstable wind slabs may exist.  Plan routes that provide a buffer and margin for error when navigating around slopes below cornices or any other wind loaded terrain.

    (1/7/2023)

    Size D2 wind slab avalanche on Incline Peak, Mount Rose area, NV. Crown line below the rocks is difficult to see, but it's there.

    Photo: Public

  • Persistent Slabs

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

    There are some indications of an emerging persistent slab avalanche problem with localized distribution. 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 8,300' elevation range in the Border Ruffian and Blues Lakes areas south of Carson Pass. Observations targeting this layer at various elevations in the Independence Lake, Donner Summit, and Mount Rose zones have not revealed any faceting or weakness on this specific layer. Substantial unknowns remain in regard to the areas where this layer is weak and problematic.

    In any areas where this layer is weak and problematic, it currently is and will continue to receive stress from the load of new snow and possibly rain during the current storm cycle. An avalanche that fails on this crust/facet layer would fail at a minimum of 2 feet deep in the snowpack, likely have wide propagation, and could be triggered from low on a slope or from the side. If you trigger any snowpack collapses, whumpfing noises, or snow surface cracking, pull back into lower angle terrain and consider avoiding NW-N-NE aspect avalanche terrain in the area.

    (1/7/2023)

    Jan 4 rain cust in the snowpit wall. Mt. Lola, Independence Lake area, CA.

    Photo: SAC

Avalanche Discussion

Storm slab avalanches in wind protected below treeline areas are unlikely today but not impossible. For any localized areas that exceed the expected forecast snowfall amounts of less than 10 inches of new snow, watch for snow surface cracking and pull back into lower angle terrain if cracking is present.

Recent Observations

  • Size D1 and size D2 wind slab avalanches were reported yesterday on N-NE-E aspects.
  • Widespread areas of intense blowing and drifting snow have occurred near treeline and above treeline. Drifting snow has also been observed in some open areas below treeline.
  • Additional unstable snowpit test results were reported yesterday with propagation observed along a thin facet layer on top of the thin Jan 4 rain crust. So far this weak layer has only been observed in the Boarder Ruffian and Blues Lakes areas south of Carson Pass.
  • Some surface hoar buried under the current storm snow was observed yesterday in localized areas south of Carson Pass.

Regions covered