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Out of date — this forecast expired 11 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

LOW avalanche danger exists for all elevations and aspects. Small avalanches in isolated areas are quite possible given the current snowpack structure. Triggering is unlikely, but far from impossible. This fits the definition of LOW avalanche danger. It is a myth that LOW danger equals no danger. Exercise best practice backcountry travel techniques and manage terrain wisely.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Small avalanches in isolated areas remain an ongoing concern. Redistribution of snow on the ground has created small pockets of wind slab on all aspects near and above treeline. Any above treeline areas that look to have a nice swath of continuous snow cover are highly suspect for a wind slab problem. Some slabs are hard and may sound hollow. Consider consequences of a small avalanche in terms of secondary terrain hazards below such as rocks, trees, cliffs, and terrain traps.

    Near treeline and below treeline NW-N-NE aspects with protection from NE winds are harboring pockets of isolated instability in the form of storm and/or wind slab on top of faceted snow. The firmer snow over softer snow structure is easily identified and the faceted weak layer has been observed both mid height in the snowpack and at ground level. Poke, prod, and investigate the snowpack. Human triggered collapse, whumpfing sounds, or unstable snowpit tests results are all reasons to back away to lower angle terrain.  

Avalanche Discussion

Significant spacial variability exists across the forecast area. In some locations no evidence of instability is observed. Within other sections of the forecast area, slopes of similar aspect and elevation are revealing isolated skier triggered collapse/whumpfing and associated unstable snowpit test results. Stay on your game and anticipate isolated packets of instability that could lead to small human triggered avalanches. Just because you or your buddy did not see evidence of instability yesterday does not mean that you will not find it today in a different location.

Recent observations from around the forecast area have pointed to concerns with mid height and basal facets near treeline and below treeline on NW-N-NE aspects. During the warm period prior to the last storm cycle, these layers were observed to round and gain strength. With plummeting snowpack temperatures post storm, these layers have returned to a faceting regime. The shallow snowpack is allowing for strong snow temperature gradients and these weak layers are now becoming weaker. These faceted weak layers have been observed both at ground level and at mid height within the snowpack. In either case there is a slab resting on top of these weak layers. The basal layer often has a fair bit of anchoring, the mid height layer tends not to have any anchoring. Again, expected avalanche size is small and triggering is unlikely, but isolated areas of instability are out there.

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