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Out of date — this forecast expired 13 years ago.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

Some pockets of MODERATE avalanche danger still exist on near treeline 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 where these pockets MODERATE avalanche danger still exist. 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 to recreate on snow 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 from the past 3+ weeks have shown the greatest amount of continued instability in the Carson Pass and Pole Creek/Deep Creek areas. 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, it only takes finding that one hidden trigger point to start a failure that could take down the whole slope. Using the terrain to avoid the avalanche hazard by recreating on lower angle slopes that remain disconnected from steeper and deeper terrain represents a fun and safe plan when conditions like this exist.

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

Avalanche Discussion

Yesterday on Rubicon Peak, observations yielded inconsistent results. Some tests pointed to a more stable snowpack and other tests indicated that fractures can still travel along the persistent weak layer. Observations have shown similar inconsistent results 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, and that stability or instability has become difficult to access.

Recently, the Carson Pass, Pole Creek, and Deep Creek areas have shown continued obvious signs of instability. The West Shore 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 areas also have the most shallow snowpack with more exposed rocks, ground, trees, bushes, logs, stumps, and other obstacles.

Regions covered