Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Weak snow below the surface could still cause problems today in sheltered or exposed terrain. Areas where wind-blown snow has accumulated on typically cold shady slopes are especially concerning.  Watch out for places with signs of recent blowing snow or other signs of instability including snow surface cracking, audible collapse, or recent avalanches.

Avalanche problems

  • Persistent Slabs

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

    Could no avalanches occur today? Sure. Would someone triggering an avalanche in wind-loaded terrain that broke wider than expected or was triggered from below or to the side of the path be a huge surprise? Not really. The weak snow (facets) that formed during the month of dry weather on NW-N-NE aspects may not hold up to the additional load of a person in some places. Areas where wind-blown snow has accumulated on top of the weak layers are especially suspect since more of a slab may exist in those zones. In other places, the recent snow on top of the weak layers may not represent enough of a slab yet for a persistent slab problem. The persistent weak layers exist above about 8500 ft on the northerly aspects. Higher elevations and more shaded slopes hold weaker snow. Significant uncertainty surrounds both the buried weak layers and whether or not a slab exists above them.  What is certain is the consequences of even a small avalanche could be severe in this shallow early-season snowpack.   

    Due to this uncertainty and the potential consequences of getting caught in an avalanche, it is best to play it safe today. Carefully evaluate any slope before you commit to it especially in areas where wind slabs may have formed on top of the buried weak layers. Cornices above a slope, drifted snow, and wind-created surfaces textures can all help identify where wind-loading may exist. If this wind-loading occurred on a NW-N-NE aspect, then the persistent weak layer likely exists below the wind-drifted snow. It is also not impossible for a problem to exist in a sheltered area where more new snow accumulated. If any signs of instability like whumphing or cracking or collapsing exist, stick to lower angle simpler terrain. Those lower angle slopes will offer more supportable snow conditions and will be easier to avoid buried obstacles on.  

    If any avalanches do occur today, they would behave more like persistent slabs. Remote triggering from far away or from the bottom of the path could be possible. They could break wider and travel farther than expected.

Avalanche Discussion

* 6 to 12 inches of light, cold new snow exist on the snow surface across the forecast area. On NW-N-NE aspects above 8000 - 8500 ft. this new snow rests on top of 1-3 ft of old snow comprised of crusts and weak layers of surgery snow (facets).  Below about 7,800'-8,000' was a mix of patchy snow cover and bare ground. Almost all SE-S-SW-W aspects were snow-free with continuous bare ground exposed.

* Snowpit data from 2 areas (Tamarack Peak and Carson Pass) indicated that weak layers in the old snow remain weak. 

* Observers reported some small signs of wind slab instability including minor cracking on wind-loaded test slopes and small slides around cornice features.

Regions covered