Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A weak and problematic snowpack exists in portions of the forecast area.  Evidence of snowpack instability is often not obvious at this time. Thoroughly assess the snowpack before committing to avalanche terrain on shaded slopes. Opt for lower angle, non-avalanche terrain if any indications of instability are present.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Faceted, weak sugary layers of snow mostly within the lower half of the snowpack remain problematic. The snowpack structure changes with elevation, with a high level of variability in the degree of layer weakness and overlying slab strength depending on location. Currently, the areas with the most frequent signs of instability are found on NW-N-NE aspects above about 8,000' to 8,300'. Snowpit tests continue to show weakness and unstable results on these well developed weak layers.  Any avalanche involvement with this persistent slab problem could have high consequences from trauma due to our rocky, shallow snowpack.

    Unless you are specifically looking, signs of instability associated with the current avalanche problem are often not obvious. Utilizing non-avalanche terrain under 30 degrees in steepness without steeper connected terrain above is a good strategy to minimize exposure and manage the associated uncertainty with this persistent slab avalanche problem. 

Avalanche Discussion

A weak faceted (sugary) snowpack exists on most NW-N-NE aspects above about 7,400'.  Near and below about 8,500', faceted snow exists around and in between rain crusts. Gaining elevation above 8,500', rain crusts gradually disappear or decompose and the lower half of the snowpack becomes nearly all weak faceted snow. Generally speaking, the higher up you go on wind protected NW-N-NE aspects, the weaker the snowpack. These weak layers are well developed, with depth hoar found at the base of the snowpack in many areas. Low sun angles that leave northerly aspect slopes in the shade all day combined with long nights have kept weakness in our shallow snowpack ongoing.

There is still the potential to hit many obstacles (rocks, logs, open water, bushes, etc.) that are barely covered (or not) by the shallow snowpack. This is especially true in areas below 7,500' and in very rocky areas up to at least 8,000'. Anticipate encountering a different snowpack structure and a different set of travel conditions if you are moving from one place to another around the forecast area.

Regions covered