Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

While a small slab of wind drifted snow or a soft slab above old weak snow may still lurk on an isolated piece of terrain, avalanches are unlikely overall. Icy scoured surfaces and variable uneven snow could make travel challenging. The avalanche danger will remain LOW for today and tomorrow. Expect an increase in avalanche danger Friday night and Saturday as new snow and wind impact the forecast area. This forecast will be updated at 7am on Saturday.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    The Dec 11 facets still exist in the snowpack. Data and observations indicate that avalanches on this layer have become unlikely on a regional scale for a variety of reasons. First, this persistent weak layer seems to have gained enough strength to support the snow above it, and second, the snow above it has gotten less slab-like in some areas. This respite from persistent slab avalanche problems may be short-lived. Observations also show that new snow loading could reactivate this layer. With snow forecast for Friday night and Saturday, this persistent slab problem will be back.

    While unlikely, it is not impossible that this weak layer may still remain active on some isolated terrain feature due to variability associated with this layer. Keep an eye out for whumpfing sounds, cracking, and/or unstable snowpack test results. Limit exposure to avalanche terrain by having a trip plan, traveling one at a time through avalanche terrain, and regrouping well out of runout zones and avalanche terrain.  

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Shifting winds have blown snow back and forth across ridgelines a few times this week. In many areas, the winds have left icy scoured surfaces or even dirt on exposed slopes creating treacherous travel conditions and the potential for long sliding falls. The slabs of wind drifted snow remaining are firm and difficult to break. Since very little snow remains available for transport, new wind slabs should have a hard time forming today and tomorrow. Wind slab avalanches should remain unlikely on a regional scale. Some small wind slabs may not be impossible in complex terrain where a small avalanche could have serious consequences. Once new snow and wind start to impact the area on Friday night into Saturday new wind slabs will start to form and wind slab avalanche will become problematic again.

Avalanche Discussion

* Small stiff wind slabs 3 to 4'' thick existed on some slopes on Silver Peak (North of Olympic Valley) and near Woods Lake (Carson Pass). Ski kicks did produce some minor cracking in these wind slabs. Firm, icy, scoured slopes and variable wind affected surfaces were reported in near and above treeline terrain on Incline Lake Peak, Silver Peak, Mt. Judah, and Carson Pass. Strong winds have also left firm wind scoured snow surfaces and wind-affected surfaces on many slopes at lower elevations.

* Signs of instability and unstable snowpack test results on the Dec 11 persistent weak layer continued to decrease. Spatial variability continues throughout the forecast area with some areas still reporting unstable snowpack test results. Data also indicates that additional snow load expected on Friday night into Saturday could reactivate this weak layer.

* Some areas of soft cold snow still exist on sheltered northerly facing slopes in near and below treeline terrain. 

Regions covered