Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Varying amounts of snow surface refreeze occurred last night and were weakest in the southern half of the forecast area. For travel in avalanche terrain today, get an early start this morning and exit avalanche terrain before the snow surface becomes unsupportable. Deep wet snow or signs of unstable wet snow such as rollerballs or pinwheels indicate that wet loose avalanches could occur.

Avalanche problems

  • Loose Wet

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

    Some locations, mainly in the northern half of the forecast area received a decent snow surface refreeze last night for the first time in several days. Areas in the southern half of the forecast area where air temperatures remained above freezing last night are likely to have a thinner and more superficial snow surface refreeze that was heavily reliant on the nighttime radiational cooling of the snowpack. Regardless of location, once the snow surface refreeze from last night melts away, deeper residual wet snow from the last several days will be exposed. This will bring about the possibility of more wet loose avalanches. Some of these avalanches could be large enough to cause problems for backcountry travelers, especially on long slopes where a wet loose avalanche will entrain more snow as it travels downhill. 

    Once the snow surface becomes unsupportable it is time to think about avoiding slopes steeper than about 35 degrees. Pinwheels, rollerballs, sinking into ankle-deep wet snow when you step off your sled or skis, and wet loose avalanches are all signs of unstable wet snow. If your desire is to travel in avalanche terrain today, get an early start and exit avalanche terrain before signs of deep or unstable wet snow develop.

    (4/10/2023)

    A recent wet loose avalanche in Woodfords Canyon. The debris is on top of an older debris pile.

    Photo: SAC

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    More natural cornice failures were reported yesterday following several days of prolonged warm weather with little to no overnight refreeze. While some areas received a decent snow surface refreeze last night, cornice failures remain possible today once last nights refreeze melts away. Large to massive blocks of snow falling off of overhung sections along ridgetops could cause problems on their own or trigger wet snow avalanches on the slopes below.

    Most cornice fall accidents occur during ridgetop travel and take the party involved by surprise. Stay well back from cornice edges, keeping exposed rocks or trees between you and the cornice edge. Consider avoiding travel on slopes below cornices.

    (4/11/2023)

    Large cornice collapses in Johnson Canyon occurred sometime between the afternoon of Apr 10 and the morning of Apr 11. Cracks are visible on the ridge where the rest of the cornice is separating from the ridgeline.

    Photo: SAC

Avalanche Discussion

  • Observers reported another round of wet loose avalanches and recent cornice failures yesterday.
  • Some glide cracks have formed on steep slopes in rocky areas. Like cornices, the exact timing of glide crack avalanches is notoriously difficult to predict. Avoiding travel on or under slopes with glide cracks represents the best course of action.

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