Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Hochgebirge
Keine Stufe
Waldgrenze
Keine Stufe
Unterhalb
Keine Stufe
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Kernpunkte

Early season conditions update #4

A deep slab avalanche problem has formed with human triggered avalanche activity in the Mount Rose portion of the forecast area. Feet of new snow continue to accumulate in some portions of the forecast area above 8,000' as the current storm progresses. Wind slab avalanche problems remain a concern area wide. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Large destructive avalanches are possible.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    This avalanche problem is currently believed to be specific to the Mount Rose portion of the forecast area. This geographic limitation is based on the limited collective snowpit data from around the forecast area pre-storm. This avalanche problem is known to exist on N and NE aspects where a layer of basal facets around 1 foot thick is at the base of the snowpack. Uncertainly exists as to presence/absence of this avalanche problem on NW aspects due to a lack of data. The lower elevation boundary of this avalanche problem is also uncertain due to a lack of available data but might be limited to areas above 8,500' to 8,700'.

    A human triggered deep slab avalanche occurred today on Tamarack Pk in Hourglass Bowl, more info is available here. Numerous snowpit tests on other portions of Tamarack Peak today produced unstable results on the basal facet layer. Sensitivity to triggering for this avalanche problem is stubborn and it exists in specific areas. Signs of instability may not be readily observed prior to triggering an avalanche. Conservative terrain selection of slopes less than 30 degrees in steepness and/or avoidance of NW-N-NE aspects are sound mitigation techniques for this avalanche problem.

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1

    Additional snowfall and strong to gale force SW winds will keep the concern for a wind slab avalanche problem ongoing throughout the forecast area. This avalanche problem is likely to exist in near treeline and above treeline terrain on NW-N-NE-E-SE aspects. Identify and avoid areas of wind drifted snow, especially below cornice features.

Avalanche Discussion

-Human triggered deep slab avalanche reported in Hourglass Bowl on Tamarack Peak. NE aspect, 2 to 2.5 foot crown, failed on basal facets.

-SAC forecasters encountered numerous difficult to trigger (stubborn) but unstable snowpit tests on basal facets on N aspects on other portions of Tamarack Peak.

-Some signs of wind slab formation seen near treeline in wind loaded areas.

-Remote weather stations and manual observations in wind protected areas above 8,000' indicate 6 inches to 3 feet of new snow around the forecast area thus far from the current storm (as of 5 pm Thursday evening).

See specific observations below for more info.

Abgedeckte Regionen