Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Near and above treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper. Below treeline, avalanche danger is MODERATE on all aspects that held previous snow cover on slopes 35 degrees and steeper.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Wind slabs are expected as the most widespread avalanche problem today. Wind loaded areas near treeline and above treeline on NW-N-NE-E-SE aspects will hold the largest slabs which may be up to 2 to 3 feet thick. Snowpack failure is expected to occur at or above the old/new snow interface. Natural avalanche activity may have occured last night. Isolated natural avalanches remain possible this morning. Human triggered avalanches will remain possible to likely throughout the day today.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Unstable storm slabs may exist near treeline and below treeline on all aspects that held snow cover prior to last night's snowfall. N aspects below treeline that have dry near surface facets at or within an inch or so of the old/new snow interface will have a higher likelihood of instability. Snowpack failure is expected to occur just below, at, or above the old/new snow interface with slab thickness expected at around 10 to 18 inches. Human triggered avalanches will remain possible below treeline throughout the day today. 

Avalanche Discussion

In the vast majority of locations a strong and stable snowpack capped by melt-freeze crust existed prior to last night's snowfall. In most areas, crust will exist today at the old/new snow interface. A few exceptions have been noted on north aspects where weaker faceted snow exists at the old/new snow interface.

Observations made yesterday near Grouse Rocks (Ward Canyon area) revealed foggy conditions and above freezing air temperatures that allowed for moisture to wet near surface facets that existed below treeline on N aspects in this area. At 8,300', only the top 0.5 inch of near surface facets were wet with an additional 2 to 3 inches of dry weak faceted snow below. At 7,500' more wet snow existed with wet near surface facets up to 2 inches deep on N aspects.

Other recent observations on Round Top Peak (Carson Pass area) and on Powderhouse Peak (Luther Pass area) noted that northerly aspect bed surfaces from slab avalanche activity Feb 8-9 hold several layers of weak faceted snow. These areas are higher in elevation than the observed areas yesterday in Ward Canyon. These areas may have escaped snow surface wetting, allowing for a more significant weak layer to have been buried at the old/new snow interface.

Regions covered