Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 10 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

LOW avalanche danger continues for all elevations and aspects. Isolated areas of instability are not impossible. Normal caution is advised. Early season conditions exist with numerous shallow buried and exposed obstacles in most areas.

Avalanche problems

  • Cornices

    • All elevations
    Likelihood
    Possible
    Size
    0

    Strong to gale force winds out of both the SW and NE over the past 7 to 10 days has created widespread areas of eroded snow surfaces and pockets of dense wind slab. Observations have indicated that these pockets of wind slab are generally stable, but isolated areas of instability are not impossible somewhere within the forecast area. Employing normal caution in the form of identifying and discussing potential areas of hazard with travel partners, one at a time travel in or below avalanche terrain, and moving from one well established island of safety to another will serve to keep the widest possible margin of safety.

    North aspects continue to hold faceted old snow near the base of the snowpack, usually on top of a ground level ice layer. This weak layer is found on N aspects along the Sierra Crest above about 8,300' and in the Mount Rose area above about 9,300'. Currently, triggering failure of this weak layer is very difficult and avalanche activity associated with it is unlikely. Day to day snowpit data continues to indicate that this weak layer could become problematic under future loading conditions. Normal caution is reasonable for managing this issue today, but it is well advised not to accept marginal islands of safety (ie using one or more large trees still within the runout zone as a stopping point) when dealing with this type of weak layer that is deeper in the snowpack.

Avalanche Discussion

Observations made yesterday in the upper portions of the Deep Creek Drainage (Pole Creek/Deep Creek area) revealed ongoing issues on N aspects above 8,300' where the faceted old snow layer existed in the lower portion of the snowpack. Snowpit tests repeatedly indicate that the weak layer and overlying slab hold properties that will allow for propagation following weak layer failure. Snowpit tests also repeatedly indicate that at the current time, triggering weak layer failure is very unlikely until significant new loading from snow/rain occurs.

Additional observations received from Mt. Judah (Donner Summit area) and Tamarack Peak (Mount Rose area) matched well with other recent observations from around the forecast area. The Mt. Judah observations further indicate that problematic faceted snow along the Sierra Crest is limited to N aspects above 8,300'. Both observations indicate that significant winds effects have occurred throughout the forecast area.

Regions covered