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

Firm snow surfaces this morning should melt to soft wet snow in response to strong April sun despite today's cooler temperatures. Sluffs of wet snow could become possible on steep sunny slopes. In addition to these loose wet avalanches, wet slab avalanches also warrant consideration. The avalanche danger is LOW this morning and will increase to MODERATE this afternoon.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Clear weather and below-freezing temperatures during the night should have allowed for a better refreeze. The strong April sun should provide enough warming for the firm refrozen conditions to become wet and unsupportable by this afternoon even though the forecast calls for cooler temperatures today. Loose wet avalanches could become possible on steep sunny slopes. Some of these loose wet avalanches could involve enough wet snow to bury a person especially on larger slopes or in areas where the loose wet avalanche flows into a terrain trap like a gully. 

    Safety margins based on timing and terrain can help manage potential wet snow instabilities. Recreating while the snowpack remains supportable and returning before the refreeze melts into deep wet snow or avoiding steep slopes and using lower angle terrain both represent strategies to avoid wet snow instabilities.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Forecasting wet slab avalanches is notoriously difficult and too much uncertainty exists to put a likelihood on this problem. The current snowpack structure may allow for the possibility of wet slab avalanches when water percolates down to the surface hoar layer buried on March 24. If a wet slab avalanche does occur it could involve enough snow to bury or injure a person.

    Using timing and terrain to avoid wet snow and/or steep terrain can help avoid wet slabs. 

Avalanche Discussion

Observations indicated little to no refreeze occurred on Yuba Pass yesterday and wet snow existed on all aspects before 10 am. Ski kicks and cuts triggered roller balls and pinwheels on steep sunny slopes.

Snowpit data on Yuba Pass yesterday indicated that fractures may still be able to travel along the surface hoar layer buried on March 24 especially if water collects near that layer. 

Regions covered