Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

MODERATE avalanche danger exists for all elevations and all aspects on slopes 35 degrees and steeper. New wind slabs formed near treeline and above treeline last night under gale force NE wind conditions. In wind protected areas below treeline, loose dry avalanche activity remains likely and small storm slabs remain possible. Don't let an absence of obvious clues of instability lull your party into a sense of security today.  

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    A 4 to 6 hour period of gale force NE winds occurred last night and winds remain moderate in speed out of the NE this morning. This wind redistributed snow on the ground from yesterday. Areas of significant wind scouring and wind loading are expected today in near and above treeline areas. The majority of new wind slab formation is expected on SE-S-SW-W-NW aspects. In complex terrain a mix of scoured snow surfaces and pockets of wind slab will likely coexist on N-NE-E aspects. Areas of wind scouring, cornice formation, wind pillows, and snow surface texture will provide clues for identifying suspect slopes in near and above treeline terrain.

    Areas of exposed rain crust on the snow surface are likely on windward aspects above treeline. The potential exists for long sliding falls with very difficult self arrest conditions.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    In wind protected areas below treeline loose dry avalanches will be likely in steep terrain. If choosing to venture onto slopes steeper than 35 degrees, evaluate the terrain for secondary hazards such as terrain traps, rocks, trees, and cliffs below that could greatly magnify the consequences of being pushed off line by a loose dry avalanche.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    New snow yesterday evening and last night produced one more opportunity for potential storm slabs to form in wind protected areas below treeline. Any subtle weak layers that exist within the upper portion of the recent new snow are likely to present as human triggered cracking in lower angle terrain. The depth of any storm slabs that might exist is expected to be less than 6 inches. Human triggered storm slab avalanche activity is unlikely to be large enough to bury a person unless occurring above a terrain trap such as a cliff or creek bed. This is where deeper burials can occur from small avalanches.

Avalanche Discussion

A report was received yesterday of a skier triggered wind slab avalanche that occurred near the summit of Jakes Peak (West Shore Tahoe area). Details are few, but the avalanche was reported to have occurred on an E to NE aspect around 9,100' in near treeline terrain. The size of the avalanche was estimated at 100 feet wide with a 100 foot down slope run. No one was caught in the avalanche. Crown height was not reported.

Observations received yesterday from the north side of Carson Pass in above treeline terrain on an ENE aspect around 8,800' indicated that just over a foot of new snow had accumulated in the area late yesterday afternoon under calm wind conditions. This far exceeded the forecast expectations of 3 to 5 inches. Unstable snowpit test results with propagating characteristics were noted 2.5 to 3 feet below the snow surface within the recent storm snow.

Observations made yesterday on Castle Peak and Andesite Ridge (Donner Summit area) as well as on Tamarack Peak (Mount Rose area) saw little evidence of snowpack instability. Numerous ski cuts and intentional cornice collapses in these locations produced loose dry results on the slopes below with no signs of unstable wind slabs. On Tamarack Peak shallow storm slab instabilities were noted, but did not present a significant hazard to backcountry travelers during the mid day hours.

Regions covered