Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Winds will continue loading leeward start zones today. Very large human-triggered avalanches are likely, and if released could run to valley floors. If venturing out today, it is best to keep a wide margin between you and steep terrain and avoid the runouts of avalanche paths above you.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3.5

    West and Southwest winds will carry snow across ridgelines and drift it onto north-east facing terrain and other leeward terrain features at all elevations. Wind-transported snow can accumulate and overload the snowpack much more quickly than storm snow alone. Very large avalanches are possible today in leeward avalanche paths that sit just below ridgelines near and above treeline. It's important to avoid the runouts of large avalanche paths. With good coverage at lower elevations, very large natural avalanches could run down to valley floors and into low-angle below treeline terrain. Wind slabs may have formed below treeline and large human-triggered wind slabs are possible in more exposed areas at lower elevations as well. As winds pick up this afternoon look for blowing snow on ridgelines as a n indication that natural avalanches are becoming more likely.

    Large natural wind slab avalanche.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2.5–3.5

    From late January through late February, the Eastern Sierra saw mostly clear weather and very little snowfall. This extended dry spell saw faceting of the upper snowpack on a variety of aspects and elevation. This process weakened the upper 40cm of the snowpack. Intermittent avalanche activity in small storms and wind events during the dry period has been a good indication that the layer might produce larger avalanches with another round of heavy snowfall. Over 3 inches of water and up to 60" of storm snow this week may have pushed persistent weak layers to the breaking point. Continued wind loading today in areas where the persistent weak layer is likely found means the sensitivity of the persistent slab is increasing. Persistent slab avalanches can be remotely triggered from adjacent slopes and flat terrain below a steep slope. If triggered, persistent slabs can propagate across and around terrain features that would otherwise confine new snow instabilities. There is high uncertainty with this problem so the best management strategy is to put a wide margin between yourself and the terrain where the problem may exist.

    (2/20/2023)

    Small wind slab avalanche that stepped down into older faceted snow during the last wind event around 2/14/23.

  • Storm Slabs

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

    Multiple natural storm slab avalanches were reported yesterday in mountain communities and below treeline terrain.  Storm slabs generally result from density changes within the recent storm snow created by changes in temperature and rate of snowfall during the storm. Observations from ski touring parties yesterday confirmed the "upside down" layering of the storm snow. Storm slabs should become less sensitive throughout the day as the storm snow settles. However, with this much snow, recent avalanche activity, and multiple storm slab interfaces this is still a problem today. Even in wind-protected areas use extra caution around slopes over 30° in steepness today, especially above terrain traps. This may include exposed areas under rooflines in town.

    (2/24/2023)

    Intentionally triggered soft storm slab below treeline.

Avalanche Discussion

Multiple natural avalanches were reported yesterday. These were below treeline and mostly small. The failure planes seem to have been at the new/old interface or within the storm snow.

As skies clear this morning we may have a better idea of patterns in recent activity, or crowns and debris may be covered by subsequent snow and wind.

Avalanche danger will begin to increase again this afternoon with increasing winds and the beginning of another round of snowfall tonight. Keep the danger trend in mind. Widespread blowing snow on ridgelines may mean that avalanche danger is increasing earlier than anticipated.

Regions covered