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Backcountry Avalanche Forecast
Issued
Monday, December 29, 2025 – 7:00AM
Author
Steve Mace
Eastside Region
Eastside RegionBottom Line
Use caution on wind-loaded slopes near and above treeline. Watch for signs of instability such as recent cornice formation, shooting cracks in drifted snow, and recent avalanche activity. When in doubt, stick to protected areas with lower slope angles to limit your exposure.
Avalanche Problem #1
Winds continue at moderate to strong speeds out of the north today before shifting back to a southerly flow tonight. Over the last two days, field observations have highlighted large wind deposits on polar aspects as well as bannering in the alpine resulting from our northerly winds. This means you may be able to find wind slabs on all aspects. Larger deposits on northerly and easterly aspects have been gaining strength since our last loading event, but are large in size. More recent deposits on solar aspects are likely to be smaller and more reactive. In either scenario, the areas of most significant concern will be the leeward sides of ridgelines, confined alpine couloirs, and cross-loaded gullies. Blowing snow, growing cornices, and recent avalanches will point to the most dangerous slopes. Shooting cracks in stiffer, textured surface snow means you’ve found unstable wind slabs. Stick to lower-angled slopes and sheltered terrain to limit your exposure.
Forecast Discussion
Winter sure showed up all at once over the Christmas holiday. Over the past few days, we have been able to take stock. A few days of quiet weather have allowed surface instabilities to settle relatively quickly, and field observations suggest settlement in the upper snowpack has allowed for more efficient movement. Evidence of several large avalanches failing during the last loading event can be seen throughout the range, and recent human-triggered activity on Sonora Pass to the north of the forecast area underscores the need to consider what lies at the base of the snowpack.
In northerly terrain near and above 10,000′, old snow lingered before this storm cycle. In these areas, a robust slab of new snow rests on a facet crust combo near the ground. It is unlikely that the weight of a skier will be enough to initiate failure near the ground; however, a wind slab avalanche failing in the upper snowpack may be large enough to step down to this deeply buried weak layer. If initiated, the result will be a very large and destructive avalanche. To help manage the uncertainty around this structure, limit your exposure to avalanche terrain and avoid steep wind-loaded slopes near and above treeline.
The ESAC team extends our sincere condolences to the Mammoth Mountain Ski Patrol and the greater Mammoth community. It is hard to find the words to express our sorrow for the loss of a member of the ski community. Please keep Cole in your hearts as you move in the mountains and take a moment to share your love with those close to you.
Mountain Weather
Issued
Monday, December 29, 2025 – 7:00AM
Author
Steve Mace
Mostly clear skies and relatively quiet weather continue to dominate as we close out 2025. Temperatures are expected to remain chilly with overnight lows in the single digits and daytime highs in the upper 30°s or low 40°s. Winds have been out of the northeast for the last couple of days and are expected to return to a southerly flow by tomorrow.
Unsettled weather is expected to return on New Year’s Day as a Pacific storm system approaches the West Coast. This could bring increasing winds and moderate precipitation back to the eastern Sierra as soon as Wednesday night and lasting through the weekend.
This information is provided by the Eastern Sierra Avalanche Center and describes general backcountry avalanche hazard and conditions. It does not apply to ski areas and highways where avalanche mitigation is conducted.
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