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Out of date — this forecast expired 8 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger remains LOW for all elevations. Avalanche activity is unlikely on a regional scale. Isolated areas of unstable snow may exist somewhere within the forecast area. Small and mostly inconsequential loose wet instability may occur today. Deep slab avalanches are very unlikely but not impossible.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    0

    The snowpack is generally stable. Some minor amounts loose wet instability may occur today on any aspect, especially at the mid and lower elevations. In general, areas of loose wet instability are not expected to present much of a hazard to backcountry travelers today. Keep an eye out for fresh roller ball activity as a sign of instability. If in doubt avoid steep slopes where any signs of wet snow instability, either new or old are present.

    Triggering a deep slab avalanche is very unlikely on a regional scale but cannot be ruled out entirely. Exercise normal caution such as exposing only one person at a time to avalanche terrain and moving from safe area to safe area. Keep in mind that in the unlikely event that a deep slab avalanche were to occur, avalanche size will be large (D3). Factor large avalanche size into safe area selection and do not rely on marginal quality safe areas. Anticipate potentially long avalanche runouts into treed terrain. If in doubt, increase the margin of safety by choosing less complex terrain and increasing the distance from areas of exposure to potential avalanches.  

Avalanche Discussion

* Snowpit data was collected yesterday at the site of the March 4th Negro Canyon deep slab avalanche (Donner Summit area). Significant rounding of the once faceted layer of concern was observed. Snowpit tests at this location showed a significant increase in stability.

* Snowpit data collected yesterday in two ridgetop locations on Becker Peak (Echo Sumit area) showed a lingering, difficult to trigger potential for deep slab instability.

* Other recent observations from around the forecast area targeting the recent deep slab problem have overall shown signs of increasing stability. General trends in snowpit data are that the once faceted weak layer of concern is located 3 to 6 feet deep in the snowpack, remains significantly less dense than the slab above it, and often presents as loose grains. Varying degrees of rounding of the once faceted snow have be observed. In some locations, faceted crystals are no longer visible under magnification. Snowpit tests indicate that it is difficult to trigger weak layer failure (ECT, CT). Tests specifically examining propagation potential (such as the PST) tend to indicate that propagation could still occur along the weak layer in the unlikely event that snowpack failure is triggered.

* Warm air temperatures and high humidity with snow levels around 6,800' to 7,500' were reported yesterday afternoon. Wet snow surfaces and minor amounts of loose wet instability were reported below 8,000'.

 

Regions covered