Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

The avalanche danger will rise quickly as a strong winter storm brings new snow and continued gale-force winds. Slabs of wind-blown snow and storm snow will avalanche on steep slopes during this blizzard. Avalanches will be very likely by this afternoon, and traveling on, near, or below steep slopes is not recommended during this storm. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–3

    Wind slabs will continue to grow in size and extent as the gale-force SW winds keep piling wind-blown snow onto slopes near ridges, on open wind-exposed areas, and in gullies. The wind-blown snow will combine with the new snow that falls during this storm, making some of these wind slabs very thick, and the resulting avalanches could be deep. Triggering wind slabs will be very likely today, and natural wind slab avalanches will become very likely by this afternoon. The largest, most fragile wind slabs will form on NW-N-NE-E-SE aspects in near and above treeline terrain, but some wind slabs may also develop in open areas below treeline due to the strength of the wind. These avalanches could be very large and travel down into below-treeline areas. 

    During this storm, traveling in, around, or below avalanche terrain is not recommended.

    (2/26/2023)

    Skier-triggered wind slab on a small wind-loaded test slope near the summit of Hidden Peak.

    Photo: SAC

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    More storm slab avalanches were reported yesterday. One failed at the base of the storm snow 2 ft below the surface. Storm slab avalanches will become very likely this afternoon as new snow accumulates and snowfall intensity increases. The fresh snow will add more storm snow on top of last week's snow and could cause weaknesses in or below that previous storm snow to break. Some large storm slab avalanches that involve feet of snow could occur. 

    Traveling in, around, or below avalanche terrain is not recommended during this storm. Any steep slope could be dangerous, even in tree-covered areas. 

    (2/26/2023)

    Storm snow failing on the old snow interface in Cold Stream Canyon in below treeline terrain.

    Photo: Public

Avalanche Discussion

Recent Observations:

  • More human-triggered storm slab and wind slab avalanches were reported yesterday. 
  • Intense blowing snow occurred in near and above treeline areas yesterday. Some blowing snow was reported in open areas below treeline as well. 
  • Several weaknesses still exist in the recent storm snow, including graupel, density changes, and weakness at the new snow/old snow interface on softer old snow. In some areas, this interface also has a thin crust near it. 
  • Some layers of old graupel, facets, and buried surface hoar still exist in the old snow below all of the recent storm snow on some NW-N-NE aspects. So far, no avalanche activity or signs of instability has been reported on these deeply buried old layers. Still, it is not out of the question that one of them could break as the load on top of them continues to increase dramatically during this storm cycle. 

Regions covered