Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Windslabs ranging in size and sensitivity exist near and above treeline, and fresh slab development is expected to continue throughout the day. Expect avalanche hazard to rise quickly this evening as a powerful winter storm enters the region.  When in doubt, choosing travel routes with lower slope angles in sheltered terrain will limit your exposure.

Avalanche problems

  • Wind Slabs

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

    Strong winds and moderate amounts of fresh snow over the past 24 hrs have created unstable slabs on leeward terrain features near and above treeline. Expect continued slab development today as strong winds continue out of the southwest.  A powerful winter storm is expected to move into the area this afternoon, with increasing precipitation rates after 4 pm. You can expect slabs of unstable snow to increase in size and sensitivity quickly as this storm moves into the region. Blowing snow, recent drifting, hollow drum-like snow surfaces, and shooting cracks in surface snow are all signs that indicate nearby wind deposits. Strong winds can transport snow in surprising ways. It may be possible to find isolated areas with fresh windslab development below treeline. Be suspect of terrain features that encourage drifting, such as the leeward sides of ridgelines, alpine couloirs, gully features, and cross-loaded depressions. Sheltered terrain with lower slope angles will offer safer riding opportunities.

    (2/17/2024)

    Recent wind slab avalanche. 2/17 - D1 Sherwin Ridge - Mammoth Area

    Photo: Steve Mace

  • Persistent Slabs

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

    While triggering a persistent slab avalanche has become unlikely, it will not be impossible. In areas with a deeper snowpack (near the crest from Mammoth to June), basal facets are buried more deeply, and human triggers are less likely. In areas both to the north and south, basal facets are more shallowly buried and have shown more recent signs of instability, but the distribution of concerning areas is more isolated in nature. If triggered, a resulting avalanche is likely to involve the full depth of the snowpack and may be unsurvivable. Areas of greatest concern can be found in regions with a generally shallow snowpack, and on slopes with shallowly buried rocks, trees, and convex rollovers that will act as good trigger points. We are expecting a substantial amount of snow over the next few days. This load of water weight will further test these buried weak layers, increasing the size potential and reactivity. Choosing lower-angle terrain with uniform snow coverage will limit your exposure.

    (1/17/2024)

    Profile of a trigger point for a slope scale collapse at 9,600' on a N aspect, in the Mammoth Lakes Basin. The persistent weak layer of Faceted grains bured on 1/2/24 is near the surface above the rock slab and drops deeper where the height of snow is over a meter. The snow was weaker in this area than on the wind-loaded slope I had just crossed. My weight broke into the weak layer and caused the whole slope to collapse.

    Photo: Everett Phillips

Avalanche Discussion

The focus remains on windslab instabilities during daylight hours today. This concern is greatest in the northern half of the forecast area and along the Sierra Crest, which has received significantly more snow over the past 24 hours.

Avalanche hazards will rise quickly this afternoon and into the evening as a potent winter storm impacts the region. Storm instabilities, both slabs and sluffs will become increasingly likely at all elevations. It will be important to monitor precipitation rates closely if you venture into the backcountry today.  Leave room to adjust your plans accordingly if the storm arrives earlier than expected.

Regions covered