Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Warm weather and strong March sunshine will create wet snow that could slide down sunny slopes today. Additionally, some unstable drifts of wind-blown snow may still linger on slopes near ridges. If you see signs that these problems might exist like recent avalanches, cracks in the snow, rollerballs, or pinwheels, moving out of avalanche terrain is a good idea.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    The NE winds continued to scour snow away from NE-E aspects and load N-NW-W-SW-S-SE aspects yesterday. Some of the wind slabs formed by these NE winds could remain unstable, and human-triggered wind slab avalanches may still be possible today. Wind slabs will most likely exist near ridgelines or on cross-loaded terrain features like gullies. Larger wind slabs will exist in areas that received the most new snow. In areas that received less new snow, the wind slabs will remain small and not extend very far from the ridges. Today's strong sunshine could also help to weaken some of the wind slabs, especially those on the SE-S-SW-W aspects. 

    Clues like blowing snow, ripples in the snow surface, and drifts of snow can help identify where wind slabs have formed. Snow surface cracking provides a good sign that the wind slabs remain unstable. Watch out for avalanche terrain on the downwind side of ridgelines that appears filled in and smooth compared to the surrounding terrain. Identify these areas and move around them with increased caution.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    The strong, late-March sunshine and daytime highs in the upper 40's to low 50's will allow wet snow to form on sunny slopes today. Wet loose avalanches will be possible and could entrain enough snow to cause problems for backcountry travelers. Long steep slopes and terrain traps like gullies, cliffs, and creeks can magnify the consequences of these avalanches. Areas around rocks and trees or in gullies will warm up first followed by open sunny slopes sheltered from the wind. Wet snow will be most prevalent on the E-SE-S-SW-W aspects, but some wet snow could also form on some northerly aspects due to the high sun angles at this time of year.  NE winds at the upper elevations may help limit warming on some upper elevation slopes. 

    Signs of potentially unstable wet snow include rollerballs, pinwheels, or simply boot-top deep wet snow. Traveling on lower-angle terrain that is not below avalanche terrain or moving to an area where the snow remains cold represent good strategies to avoid wet snow problems. 

Avalanche Discussion

  • Observers around the forecast area reported blowing snow along the upper elevation ridgelines yesterday. Ski kicks triggered small test slope failures in the Donner Summit area. Snowmobile cuts in the Blue Lakes area did not produce signs of wind slab instability. 
  • Some rollerballs occurred yesterday, and snow surfaces became heavy and wet on some sunny slopes. 
  • Snowmelt on SE-S-SW aspects has exposed bare ground in many areas. Over snow travel options are limited on these aspects.
  • The old facet layer that was buried on Feb 14 still exists on some NW-N-NE aspects. It is unlikely that the recent snow has added enough load to result in avalanche problems on this layer.

Regions covered