Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
1 · Low
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 13 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Pockets of MODERATE avalanche danger may still exist on near and below treeline NW-N-NE aspects steeper than 32 degrees where consistent snow cover exists. Persistent slabs continue to lurk in these areas. Human triggered avalanches remain possible in these places. Lack of snow in all other areas has made the avalanche danger LOW or non-existent.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Human triggered persistent slab avalanches remain possible on some NW-N-NE aspects in near and below treeline terrain. These slopes also represent the best places for snow travel because they have the most consistent snow cover. Areas where a shallower snowpack connected to deeper snow exists or trigger points like shallowly buried rocks represent the most likely places to trigger an avalanche on these slopes. Field observations since Dec. 7th have shown variability concerning where the snowpack may remain unstable and where more stable conditions exist. In general observations from the Yuba Pass, Mount Rose, Donner Summit, West Shore Tahoe, and Echo Summit areas have shown significantly less ongoing instability and in some cases stable conditions near and below treeline on NW-N-NE aspects.

    The increase in variability and uncertainty associated with the persistent slabs makes accessing snowpack stability difficult. Even though most observations may point to a stable slope, finding one hidden trigger point could start a failure and cause an avalanche. Traveling on slopes less steep than 30 degrees that remain disconnected from steeper and deeper terrain represents a fun and safe plan when persistent slabs like this exist.

    These kind of avalanches should remain small due to the lack of snow; however, getting caught in one of them will result in collisions with rocks, logs, or trees due to that same shallow snowpack.

Avalanche Discussion

Variable snow conditions and inconsistent data concerning stability existed in the Deep Creek drainage (more info, snowpit) yesterday. Snow surfaces ranged from breakable crusts to soft unconsolidated snow to hard icy surfaces to dirt. In areas where consistent snow cover did exist (mostly northerly aspects near the creast above 7800 ft.) the Dec. 7th facet layer remains buried in the bottom third of the snowpack. Some tests on this layer indicated that fractures can still travel along the persistent weak layer, and other tests pointed to a more stable snowpack. For the first time since Dec. 7th, no human triggered collapsing or cracking occurred in the Deep Creek area.

Observations have shown similar inconsistent results and variable conditions across the forecast area. In some areas the Dec. 7th facet layer remains active and in other areas no signs of instability exist. Overall observations show a snowpack whose stability or instability varies greatly from slope to slope or even across an individual slope. Stability or instability has become difficult to access.

Recently, the Carson Pass and Pole Creek areas have shown continued obvious signs of instability. The West Shore and and Deep Creek areas have shown a mix stable and unstable results. The Yuba Pass, Donner Summit, and Mount Rose areas have shown better overall snowpack stability with few or no signs of instability. Of course these more stable areas areas also have the most shallow snowpack with more exposed rocks, ground, trees, bushes, logs, stumps, and other obstacles.

Regions covered