Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

MODERATE avalanche hazard exists for All Elevations on Northerly-Easterly aspects. Yesterday’s fresh snowfall (3-12inches) and increasing southwesterly winds today will build fresh wind slab adjacent to ridgeline and in complex terrain. With the clearing skies, take a good look at current snow conditions and associated terrain since our lengthy holiday storm cycle.

Avalanche problems

  • Wind Slabs

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

    3-12inches of low-density snow fell across the forecast zone yesterday with the deepest accumulations centered around the Mammoth area. Yesterday, SW winds blew their strongest in the Mammoth zone, with lighter velocities found elsewhere to the north and south. SW winds are expected to increase throughout the day, reaching the 50mph range at ridgetop by afternoon which will give ample opportunity to transport yesterday’s snowfall to the leeward aspects of NW-N-NE-E-SE. The Upper to Middle elevation bands are of most concern. The enerally light to moderate winds yesterday and overall cold temperatures will have kept the new snow relatively light and easily transportable. Be on the look out today for blowing snow, fresh, fat looking pillows of deposited snow, and uneven snow surfaces. Areas adjacent to ridgeline, cliff bands, rock outcroppings, and convex roll overs are all terrain features where wind slab will be possible.

  • Loose Dry

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

    Relative cold temperatures (single digits to teens Fahrenheit) and light to moderate winds yesterday/overnight will all contribute to Northerly-Easterly sheltered terrain potentially still harboring a light blanket of freshly fallen snow. These light powdery surface conditions are conducive to Dry Loose avalanches/sloughing so keep it in mind if you are venturing into steep and constricted terrain where a small point release may gain enough volume to push you over or drag you into terrain you don’t want to be in.  

Avalanche Discussion

A mighty 6-10+inches of water content and many feet of snow have built up our snowpack since last Wednesday the 22nd. This intense loading caused large to very large avalanches throughout the forecast zone that flushed out much of the weak faceted snow near the base of our snowpack, or buried it so deeply that it is no longer sensitive to a surface trigger. We have maintained the “Persistent Slab” avalanche problem on the avalanche bulletin throughout the Christmas storm cycle and at this point feel that there has been enough time, and significant settlement and adjustment of the snowpack to the new added weight that it is unlikely a skier trigger will initiate a deep persistent slab avalanche. Recent stability tests all suggest this. The dynamic nature of snow and the large forecast zone though calls for awareness of this condition and that it should still be kept in mind as we travel through the landscape. Steep slopes with snow coverage prior to December are where this concern lies (>~9,200feet, W-N-E-SE facing). The conservative call is to seriously evaluate whether you need to travel up or down on steep rocky terrain where a shallow spot may be more easily found.

For reference, Mammoth ski patrol triggered very large Deep Persistent Slab avalanches failing in weak facets near the ground this past Sunday with explosives. Additionally, some previous, very large natural avalanches in the backcountry were reported when there was enough visibility this past Sunday. While it’s not certain if these natural avalanches failed in old deeply buried weak layers, what is certain is that all these avalanches (natural and patrol triggered) required very intense new snow loading to release.

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