Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Wed
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Out of date — this forecast expired 3 years ago.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 shallow snowpack exists below the recent storm snow we received last week.  Where strong wind blown or consolidated snow sits on top of this weak snow, avalanches remain possible.  Early season conditions with rocky and shallow snowpack areas continue throughout the forecast region.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    A weak faceted snowpack exists on many NW-N-NE aspects throughout the forecast region.  The most recent storm snow has not been enough load to cause avalanches on this weak layer up to this point, with a high level of variability in the weak layer and overlying slab strength depending on location.  Snowpack tests still continue to show unstable results on multiple layers in our snowpack at some locations.  Areas with wind blown snow or consolidated recent storm snow on top of this weak snowpack structure, are the most concerning areas for a persistent slab avalanche to occur.  

    If a persistent slab avalanche did occur, it could break wider than expected and be remotely triggered.  Any signs of instability encountered (shooting cracks, whumpfing sounds, snowpack collapses) would mean that you are in a location that has all the ingredients for a persistent slab avalanche to occur.  If an avalanche did occur, it could result in serious trauma from all the exposed rocks and current shallow snowpack. 

    (12/11/2023)

    Weak faceted snow below the recent storm snow.  Northern side of Hourglass Bowl.  Tamarack Peak, Mt. Rose area.

    Photo: SAC

Avalanche Discussion

A weak faceted (sugary) snowpack exists on most NW-N-NE aspects. As elevation increases expect to find layers of faceted snow in between rain crusts. Above about 8,500', rain crusts disappear and 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.  Early season NE wind events previously scoured some exposed slopes down to dirt, rock, or ice.  The distribution and strength of the faceted snowpack varies greatly throughout the forecast region.

Cold temperatures, clear skies, low sun angles, and long nights will continue the faceting process in our shallow snowpack further decreasing the snowpack structure.

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. Areas with a supportable mid snowpack rain crust in the 7,500’ to 8,500’ elevation range provide the most usable snowpack. 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