Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Human-triggered wind slab avalanches will be possible today on wind-loaded slopes and some human-triggered storm slab avalanches may be possible on sheltered slopes. MODERATE avalanche danger exists at all elevations. If more snow falls than forecasted, the avalanche danger could rise to CONSIDERABLE. Evaluate the snowpack and terrain carefully to identify where problematic storm slabs and wind slabs may exist and plan travel routes to avoid areas with these avalanche problems.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    Gale force southwest winds and new snow will form wind slabs on leeward aspects today. These wind slabs will build quickly and human-triggering of these wind slabs will be possible today and may be likely in some of the most heavily wind-loaded areas. Depending on the amount of snow this fast moving storm deposits, some wind slabs could reach 2 to 3 ft in depth in heavily wind-loaded areas. If the lower end of predicted snowfall occurs, the wind slabs will remain smaller. If the upper end of forecasted snow or more snow than forecasted falls, wind slab avalanches will grow larger and more problematic. Wind-loaded N-NE-E aspects and cross-loaded NW and SE aspects in near and above treeline areas above 7500 ft. will hold the largest and most fragile wind slabs, but some smaller wind slabs could also exist in wind-loaded below treeline areas due to the strength of the wind.

    Identify where wind slabs may exist using clues like blowing snow, cornices, wind pillows, ripples across a slope, and other wind created textures and use this information to plan a route that avoids the wind slabs.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Changing snow levels and snowfall rates that may reach or exceed 2 inches per hour could allow human-triggered storm slab avalanches to become possible on steep open slopes in sheltered areas this morning. The actual amount of snow accumulation we receive will determine the potential size of this avalanche problem. Snowfall amounts on the lower end of the forecasted range will mean smaller storm slabs, while snowfall amounts on the higher end of the forecasted range will mean larger more problematic storm slabs. 

    Human-triggered cracking, recent avalanche activity, feeling softer layers below harder layers as you probe can all indicate storm slab instabilities. Make careful observations while traveling in the backcountry to identify where storm slabs may exist. 

Avalanche Discussion

Observations from Rubicon Peak and Incline Lake Peak yesterday showed a snowpack with a thick, strong rain crust buried about 25 to 30 inches below the surface. The layers of snow around this crust appear to have bonded well to the crust. Above the crust, the snowpack showed good bonding within and between the layers of snow all the way to the surface. Variable snow surfaces existed ranging from soft unconsolidated snow on sheltered N-NE aspects to firm scoured surfaces and sastrugi on exposed N-NE-E aspects to breakable refrozen sun crusts on open E-SE-S aspects to wet sticky surface snow below 7800 ft. on N aspects. 

Regions covered