Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

New wind slabs that form today may be sensitive on leeward terrain features. Watch for blowing snow or cracking in rounded rippled drifts. Though signs of instability have decreased, weak snow at the base of the snowpack is still a concern. In areas with a shallower or variable snowpack, you are more likely to trigger a destructive avalanche. When in doubt, default to sheltered terrain with low slope angles and deep snow cover. 

Avalanche problems

  • Wind Slabs

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

    On some shady slopes, older wind slabs can still crack around you where they rest on weaker, faceted snow. In areas with soft snow at the surface, new drifts can form as southwest winds increase throughout the day. Look for snow blowing onto steep open slopes. Use caution around terrain features that encourage drifting. You’re most likely to trigger a stiffened slab of wind-textured snow on the leeward sides of ridgelines or the sidewalls of couloirs and gullies. You can look for shooting cracks on small test slopes to understand how slabs may behave in bigger terrain. You can avoid the problem by riding softer snow on sheltered slopes. A relatively small avalanche breaking in the upper snowpack has the potential to step down to weak layers at the base of the snowpack and may result in a much larger and more destructive avalanche.

    (2/11/2024)

    Cracking on steep W test slopes NTL. Failure plane is down 20 to 30cm - grains at interface are stellar precip. particles.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3

    You are more likely to trigger a large persistent slab avalanche in areas with a generally shallow snowpack. The most recent signs of instability - shooting cracks and collapsing - from buried weak layers have been in the mountains around Bishop. In areas with a deeper snowpack, shallowly buried rocks, trees, and convex rollovers can act as trigger points. Persistent slab avalanches can be triggered remotely from flat terrain below or adjacent to steeper slopes. They can propagate widely, connecting multiple start zones. If triggered the resulting avalanche may involve the full depth and weight of the snowpack. If you decide to step out into more consequential terrain, you can stack the deck in your favor by riding planar or concave slopes with a deep, uniform snowpack. Traveling on slopes less than 30º without overhead hazards is the most effective strategy for reducing risk.

Avalanche Discussion

More on the persistent slab problem:

The likelihood of triggering an avalanche at the base of the snowpack varies between drainages and, in some cases, across the same slope. In wind-battered alpine terrain, there is a high amount of uncertainty over the distribution of weak layers. However, steep rocky start zones have produced the largest avalanches this season. At lower elevations, weak snow under a slab is most likely on shady, open slopes with smooth ground cover. On some low-elevation slopes, it has been covered by melt-freeze crusts. On others, the weak layer is broken up by ground anchors and is less consistent. The persistent slab structure is most widespread near treeline and mid-slope. 

In many areas, weak sugary depth hoar near the base of the snowpack has been showing signs of improvement. Between Mammoth and June, these grains are buried deeply under hard slabs. In these areas, triggering a persistent slab may be less likely, but if you find a shallow trigger point, the resulting avalanche would be quite large.

Coverage since early February has increased, and so has access to avalanche terrain from Convict Lake to Bishop Creek. Initial reports from these areas describe a shallow snowpack layered over early-season weak layers. Following the last storm widespread signs of instability were reported, such as slope scale collapses and long shooting cracks. While signs of instability have decreased, human-triggered persistent slab avalanches are more likely in these areas.

Regions covered