Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

A good overnight refreeze and cooler windy weather will mean firm snow surfaces this morning. As the day warms up and the refreeze melts, avalanches of loose wet snow may become possible on steep sunny slopes this afternoon. Cornice fall will also remain possible. This afternoon MODERATE avalanche danger will form at all elevations. This is the last avalanche forecast for the season.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Near-freezing temperatures combined with mostly clear skies during the night should have formed a thick layer of firm refrozen snow at the surface. Cooler temperatures and continued strong wind today will extend the time that this overnight refreeze remains supportable. "Cooler" in May still means daytime highs in the 50's above 7000 ft and long hours of intense sunshine on all aspects, so the supportable snow is unlikely to last all day. By this afternoon the overnight refreeze could melt away on some slopes exposing deep wet snow and loose wet avalanches may become possible on steep slopes. 

    Expect firm snow on all aspects this morning. Soft wet snow will form on E-SE-S aspects first and move to other aspects as the day warms up. Once the snow starts getting wet and deep, it is time to avoid avalanche terrain by recreating on lower angle terrain without steep slopes above.

    Photo: A recent loose wet avalanche in Polaris Bowl (south of Carson Pass).

  • Glide Cracks

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Falling cornices still represent a potential problem. Large pieces could break off of these overhanging waves of snow as they melt. These blocks of snow could injure a person and may entrain more wet snow or trigger a loose wet avalanche when they impact the slopes below them.

    Cornices often break farther back from their edges than expected or at unexpected times. Staying far away from the edges of cornices and not traveling underneath cornices can help avoid this problem.

     

    Photos: Debris from recent cornice failures on Red Lake Peak (Carson Pass area) and Mt. Judah (Donner Summit area).

Avalanche Discussion

* Spring melt-freeze conditions exist on all aspects and at elevations across the forecast area. Melting has also resulted in mostly bare slopes or patchy snow coverage on many southerly facing slopes and on all aspects below 7400 ft. 

* Observations from Red Lake Peak (Carson Pass area) and Mt. Judah (Donner Summit) yesterday found firm snow on most aspects in the morning. In both areas, the E-SE-S aspects had softened by mid-morning. On Red Lake Peak the NE aspects remained firm through mid-day at least, but those more northerly aspects did start to soften on Donner Summit around 11 am. In both of these areas, sun cups and runnels have formed on the snow surface. 

* Observers reported several recent cornice falls in both areas. Observers could also see a recent loose wet avalanche in Polaris Bowl (south of Carson Pass) from Red Lake Peak.

* Numerous glide cracks exist where the snowpack overlies steep slabs of rock. No glide avalanches have been reported.

Regions covered