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Backcountry Avalanche Forecast
Issued
Friday, December 26, 2025 – 7:00AM
Author
Clancy Nelson
Eastside Region
Eastside RegionBottom Line
Very dangerous avalanche conditions persist as heavy snowfall and strong southwest winds continue into the afternoon. Even if things ease up later today, natural and human-triggered avalanches will remain likely. Give it time, give it space, and avoid being on or under slopes steeper than about 30 degrees.
Avalanche Problem #1
Problem Type
Aspect/Elevation
Likelihood
Size
Strong southwest winds continue, along with heavy snowfall this morning. Cohesive slabs of drifted snow will fill in the downwind side of ridges and gullies. They’ll be building faster than they can stabilize, and natural and human-triggered avalanches big enough to bury you remain likely on wind-loaded slopes. Poor visibility could make identifying that kind of terrain difficult. Avalanche debris could run into sheltered terrain. Avoid being on or under slopes steeper than about 30 degrees.
Avalanche Problem #2
Problem Type
Aspect/Elevation
Likelihood
Size
Storm instabilities, both slabs and sluffs, will be sensitive as loading continues into this afternoon. Large avalanches failing within the new snow remain likely in places like Mammoth and close to the Sierra Crest. Snowfall rates of up to 3 inches per hour are forecast throughout this morning. Fluctuations in snow density have created storm slabs failing on steep sheltered slopes, even within town limits. Avoid being on or under slopes steeper than about 30 degrees. As significant snowfall continues, be aware of overhead hazards from roofs and road cuts in mountain communities.
Forecast Discussion
The mountains are finally white. You got new powder skis in your stocking yesterday. But don’t put the sleigh before the reindeer. This storm isn’t over yet, and the new snow hasn’t had time to settle down.
In fact, Mammoth Mountain Ski Patrol reported 2-foot deep avalanches in the limited terrain they were able to access just yesterday. Other instabilities within the storm snow include: forecasters in Mammoth triggering storm slab avalanches and shooting cracks practically from their back door, and snow sliding off the roof, burying one of our trucks. Aside from Patrol mentioning some avalanches breaking on a buried rain crust, we have not had any observations from higher elevations where the new snow has stacked up on top of the old.
Besides bare ground, all this new snow has fallen onto a variety of old surfaces and snowpack structures. Slopes on the northern half of the compass, above about 9,000 to 10,000 feet, had more continuous coverage pre-storm. Rain last weekend left a slick crust on the old surface in the Mammoth and June areas. It goes up to at least 11,000 feet on all aspects that had snow. In portions of the forecast area that did not get rained on, there was stiff windboard in the alpine, and weak facets in sheltered areas. The old snowpack, in general, was thin and composed of large, loose facets interspersed with crusts.
Regardless of the situation near the ground, the mountains will continue to get pounded by new and drifted snow through at least midday. The new snow will take time to stabilize, and it’s deep. Avalanches and deep-snow immersion remain very real hazards. Avoiding avalanche terrain is the safest way to enjoy your holiday.
Mountain Weather
Issued
Friday, December 26, 2025 – 7:00AM
Author
Clancy Nelson
The National Weather Service in Reno has extended the Winter Storm Warning for our area to 4 pm this afternoon.
Precipitation has waned overnight, though winds remain strong at all elevations, blowing snow around on webcams. Snowfall favoring Mammoth and the Sierra Crest is expected to rally this morning, with precipitation rates reaching 3 inches of snow per hour before noon. Winds and snowfall diminish later today and overnight.
The weekend looks cool and calm with more sun than clouds.
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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