Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Snow showers and winds may add small slabs to upper-elevation, leeward terrain today. You can trigger a bigger avalanche in isolated pockets where stiff wind-drifted snow rests on a weak sugary base. Thin coverage remains the primary backcountry hazard with rocks, trees, and other exposed terrain increasing the potential consequence of avalanche involvements or slips and falls.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    In isolated areas wind-drifted snow sits on weak layers of facets and depth hoar at the base of the snowpack. Though small accumulations of new snow are unlikely to overload the fragile snowpack, they could incrementally increase the likelihood of human-triggered avalanches. If triggered, the resulting avalanche could break unexpectedly and involve the full depth of the snowpack. Collisions with rocks, trees, and shallowly buried objects are likely if you get caught. Persistent slabs are slow to gain strength and can remain a concern over an extended period. Managing this problem may be more difficult for backcountry riders because poor snow coverage means that the few areas attractive for riding are generally the same slopes where the avalanche problem may exist. The best strategy is to remain patient and stick to lower-angle terrain.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    Strong winds began to build thin new slabs in north-facing terrain features at upper elevations overnight. A few inches of fresh snow today may drift into leeward slopes as well. While mostly not large enough to bury you these slabs could be a concern in steep or exposed terrain where a short ride or a tumbling fall may have serious consequences. Look out for stiff hollow feeling snow and shooting cracks in the upper snowpack, especially if you are transitioning to steep terrain around ridges at upper elevations.

    (1/6/2023) Photo: Cracking in wind slabs

Avalanche Discussion

Today's main source of uncertainty is the weather forecast for the next 12 hours. There is a winter weather advisory in effect for the forecast area, but we are unlikely to see enough wind and precipitation to substantially increase avalanche hazard. Most weather models show 2" or less of snowfall even in the most favored areas within the region. Winds are expected to decrease as the snowfall arrives meaning that wind deposition should be limited as well. If you are out in the backcountry today it will be important to confirm that actual snowfall does not outperform the forecast and to watch wind transport carefully to confirm that new slab development falls within the small size range.

More generally, the season is out to an inherently uncertain start. In many areas of the forecast region, ground anchors are still exposed and the snowpack has yet to reach minimum depth for avalanche formation. In other areas, such as the Mammoth Lakes Basin, large natural avalanches have occurred where wind-loaded slopes failed on depth hoar layers at the ground. While the persistent slab problem is isolated within the mountain range, the areas with the most ridable conditions (high elevation, and prone to wind loading) are the same ones where you are most likely to trigger an avalanche. Low snow has also affected our confidence in "how we know what we know about the snowpack". Without consistent snow coverage, travel in the mountains has been difficult. As a result, there are fewer observations to base assessments on.

In the big picture, it is difficult and potentially frustrating to operate confidently when uncertainty undermines our ability to assess hazards. In these situations, remaining patient and erring conservative may be the best strategies for managing risk. 

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