Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
View on map

Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
Open full map
Out of date — this forecast expired 13 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger is MODERATE with pockets of CONSIDERABLE avalanche danger near and above treeline on NW-N-NE-E-SE aspects due to unstable wind slabs on slopes 35 degrees and steeper. In wind protected areas below treeline and in wind scoured areas near and above treeline, avalanche danger is LOW.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Strong to gale force ridgetop winds over the past 24 hours have redistributed recent new snow on the ground. Wind loading and subsequent wind slab formation has been observed near and above treeline on NW-N-NE-E-SE aspects. Areas above 8,400' that did not receive any rain on Feb 9 had significantly more snow available for wind transport. Wind slabs up to 3 feet thick are know to exist in lee areas above 9,000'. Human triggered avalanches are possible to likely today. Natural avalanches remain possible.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3

    Weak layers of well developed facets and depth hoar remain buried deep in the snowpack on near and below treeline NW-N-NE aspects above 9,000 ft. The strong thick layer of new snow above these weak layers has made collapsing these weak layers difficult. Deep persistent slab avalanche activity is now in the unlikely but not impossible category. Areas where a shallower slab exists and around trigger points such as exposed rocks are the most likely location to trigger this type of avalanche. Since near treeline and below treeline areas above 9,000 ft. represent only a small portion of the forecast area, this problem remains isolated in distribution.

Avalanche Discussion

Observations made yesterday revealed unstable wind slabs in near and above treeline terrain. On Stevens Peak (Carson Pass area), a natural avalanche was observed around 11:30 am in above treeline terrain on an E aspect at about 9,500' with an estimated slope angle of 45 degrees. Approximate measurements of the avalanche were 100' wide, 400' vertical run, and a 3' crown. See below for photos and more info.

On Lincoln Ridge (Yuba Pass area) smaller unstable wind slabs were observed on NE aspects in near and above treeline terrain above 7,700'. Small wind slabs up to 9 inches thick cracked easily and small cornice features easily collapsed in response to the weight of a skier. Shooting cracks up to 20' long were observed as wind slabs and small cornices failed. Dense wind slabs were noted to fail on the top of a 2 inch layer of low density recent storm snow sandwiched between the bottom of the wind slab and the top of the Feb 9 rain crust. See below for photos and more info.

Regions covered