Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Sun and warm weather today could cause wet snow to slide downhill, weaken cornices, and make it easier to trigger slab avalanches where piles of wind-blown snow linger. Small areas of newly wind-drifted snow may start to form at higher elevations as the winds increase this afternoon. Watch for changing conditions to inform your travel plans and make plans to avoid being under cornices today. 

Avalanche problems

  • Wind Slabs

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

    As winds increase this afternoon, some blowing snow may pile up on the leeward sides of ridges and create small wind slabs at the upper elevations where some soft snow still lingers. Signs of instability on older wind slabs have decreased over the last few days, but some may remain unstable, especially in gullies or in complex or extreme terrain. Today's warmer weather and intense sunshine will weaken wind slabs on slopes that get direct sun, like cross-loaded SE aspects. This warmth and sun could also weaken the massive cornices lurking along many ridgelines and cause them to fail. Falling cornices or wind slabs could involve enough snow to bury or injure a person. 

    Watch out for slopes with cornices above them and slopes where blowing snow has piled up.

    (4/4/2023)

    Large cornices above NE and N facing slopes on Tamarack Peak

    Photo: SAC

  • Loose Wet

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

    Warmer weather and intense April sunshine should provide enough warming for areas of unstable wet snow to form on sunny slopes. Wet snow instabilities will start as rollerballs and pinwheels. They could progress to sluffs of wet loose snow large enough to cause problems for backcountry travelers. The largest wet loose avalanches would occur on long slopes steeper than about 35° since these avalanches entrain more wet snow as they slide downhill. Sunny E-SE-S-SW-W aspects will experience the most warming, but smaller amounts of wet snow could form on NE and NW aspects due to the high sun angles this time of year. 

    Once rollerballs and pinwheels start occurring, the snow is wet enough to slide downhill. Consider moving to slopes less steep than 35 ° or to different aspects where the snow has not warmed to reduce the risk of encountering a wet loose avalanche. 

    (4/5/2023)

    Cornice pieces falling on this SE-facing slope caused a small sluff of wet snow on Castle Peak.

    Photo: SAC

Avalanche Discussion

  • Cornice pieces dropped on a sunny SE-facing test slope did produce small wind-slab failure mixed with a sluff of wet snow. Snowpit tests and ski cuts on other wind-loaded test slopes did not produce unstable results. Most of the sunny days in March have seen human-triggered wind slabs, and several close calls have occurred this spring.
  • Some rollerballs and pinwheels occurred around rocks and cliffs yesterday, but no larger wet loose avalanches were reported.
  • Massive cornices exist along many ridgelines. Some of them have deep cracks behind them. 
  • Surface hoar existed in many open areas yesterday morning, but it had started to melt and flatten due to daytime warming by yesterday afternoon.
  • Areas of soft cold snow still existed on some N-facing slopes yesterday. 

Regions covered