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Backcountry Avalanche Forecast
Issued
Wednesday, December 31, 2025 – 7:00AM
Author
Greg Cunningham
Eastside Region
Eastside RegionBottom Line
Moderate southwest winds and light snowfall above 9000 feet may form small wind slabs above treeline on leeward slopes this afternoon. Rain on snow and warm temperatures may cause wet loose avalanches near and below treeline. Although unlikely, avalanches breaking deeply on old snow are at the back of our minds.
Avalanche Problem #1
After several days of strong wind from varying directions, you could still find old stubborn wind slabs at higher elevations. A few inches of snow may accumulate by this afternoon above 9000 feet. Light to moderate southwest winds at ridgetops can be enough to form soft, shallow wind slabs. If you travel above treeline today, look for stiff old snow that cracks below your feet. This afternoon, look out for blowing snow, cornices and new drifts on downwind slopes, gullies and couloir features.
Avalanche Problem #2
After several days of strong wind from varying directions, you could still find old stubborn wind slabs at higher elevations. A few inches of snow may accumulate by this afternoon above 9000 feet. Light to moderate southwest winds at ridgetops can be enough to form soft, shallow wind slabs. If you travel above treeline today, look for stiff old snow that cracks below your feet. This afternoon, look out for blowing snow, cornices and new drifts on downwind slopes, gullies and couloir features.
Avalanche Problem #3
Our current persistent slab avalanche problem falls in the low-likelihood, high-consequence category. It is unlikely that a human will be able to affect the old, rotten snow now buried 2 to 3+ feet down. If one did find a shallow trigger point, or a big enough trigger was involved, a resulting avalanche would be large to very large.
This is a difficult problem to manage, as one will often not receive feedback or signs of instability prior to an avalanche. The only real way to limit exposure to this problem is to avoid slopes where old snow is buried. Remember that persistent slab avalanches can be remotely triggered from adjacent slopes and from flat terrain below a steep slope. If triggered, they can propagate across and around terrain features that would otherwise confine new snow instabilities.
With new snow in the forecast, today will be a good day to step back and consider how the incoming weather will affect the existing snowpack going forward.
Forecast Discussion
The snow has been on a stabilizing trend, people have been getting out, and conditions have been excellent.
Today marks a change to an extended, unsettled weather pattern. We have three avalanche problems to consider, and you can plan on the snow surfaces changing. Today is a good day to check in and reevaluate how changing weather will impact surfaces and buried avalanche problems.
Old, weak snow exists near the base of the snowpack above 9500 feet on E, N and NW aspects. In places near the Sierra Crest, it may exist even lower. In the northern half of the forecast area, weak sugary snow is capped by a rain crust up to 11000 feet that can be identified with a probe. South of Mammoth, the rain crust is hard to find or does not exist. The elevation line for old faceted snow is also higher in the southern end of the forecast area.
In the last week, persistent slab avalanches have failed near the base of the snowpack in the forecast region and to the north. Most of these failed during the Christmas storm cycle, but several failed in the days immediately after. We have not recorded a persistent slab avalanche since 12/28.
Consider all of these changes, and adjust your mindset accordingly as we move into a week of active weather.
Mountain Weather
Issued
Wednesday, December 31, 2025 – 7:00AM
Author
Greg Cunningham
Today will be cloudy with chances of snow and rain by mid-day. Snow levels will be 9000 feet or higher. Winds have switched from northeast to southwest in the last 24 hours and will continue in the light to moderate range. By Thursday morning, expect 1 to 4 inches of wet snow above 8000 feet, and several inches above 10000 feet. The forecast calls for a lull in precipitation on Thursday night into Friday morning before winds and snowfall chances ramp back up going into 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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