Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
View on map

Avalanche danger

Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
Open full map
Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

As the storm intensifies, heavy snow and gale-force winds will create very dangerous avalanche conditions in the backcountry today. Large unstable slabs of wind drifted snow and softer slabs of storm snow will exist on steep slopes in both exposed and sheltered terrain. During the day, the avalanche danger will increase to HIGH near and above treeline and CONSIDERABLE below treeline.

Travel in or below avalanche terrain is not recommended today.

Avalanche problems

  • Wind Slabs

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

    Gale force SW winds and new snow during the night have already formed fresh slabs of wind drifted snow on wind-loaded and cross-loaded NW-N-NE-E-SE aspects. Additional wind and more intense snowfall today will cause these already fragile wind slabs to grow in size and extent. As the day progresses, expect natural wind slab avalanches to occur. If people venture onto steep wind-loaded slopes, human-triggered wind slab avalanches are very likely. By this afternoon wind slabs could grow to several feet deep. Wind slab avalanches would easily entrain enough snow to bury a person or maybe a car. In some isolated areas, it is not impossible for wind slab avalanches to break below the old snow surface on older weak snow. 

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    Snowfall rates of 2-3 in/hr and other changes during the storm will create fragile slabs of storm snow in more sheltered terrain. The soft slabs of storm snow will grow larger and more widespread as more snow accumulates today. Human-triggered storm slab avalanches will become likely on steep slopes and some natural avalanches may also occur. These storm slabs could break on weaknesses within the storm snow or may fail on the old snow surfaces. In some isolated areas, they may overload weak layers below the old snow surface like the old surface hoar layer. Storm slab avalanches could entrain enough snow to bury a person.

Avalanche Discussion

Observations yesterday on Tamarack Peak revealed mostly firm or breakable crusts on the snow surface. In some areas the morning sun softened the surface snow and some less consolidated snow existed in a few isolated spots. Observations this week have shown these mostly firm surface conditions across the entire forecast area. 

The buried surface hoar layer still exists in some places but snowpit tests and data from this week indicated that it has gained strength.

Today's intense storm will cause conditions to grow increasingly worse. The snowpack will become increasingly unstable. On top of this, the storm makes terrain evaluation, over the snow travel, and group communication difficult due to high winds, blowing snow, and low visibility. If someone gets hurt, rescue would be delayed or impossible due to dangerous conditions. Today would be a good day to catch up on your favorite book or show. 

Regions covered