Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

Another storm brings heavy rain and high elevation snow to our forecast region today.  Slabs of wind blown snow will form above the rain/snow line below ridgelines, in gully features, and in open areas.  Wet snow avalanches could occur where rain falls on snow.  Limited snow and terrain are available for recreation with early season hazards present.   

Avalanche problems

  • Wind Slabs

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

    Slabs of wind blown snow will form in near and above treeline areas today above the rain/snow line.  These wind slabs will continue to build in locations where snow is falling continuously, mainly near and above 9000' today before snow levels drop this afternoon.  Where wind slabs form above old faceted snow, potential exists for larger avalanches to break down into these older layers of weak snow especially as wind slabs get larger in size as the storm continues.

    Look for blowing snow, cornice development, and forming wind pillows as clues to where wind slabs are forming.  Identify where wind slabs will be in the terrain and plan to move around these areas of concern.  

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    This strong atmospheric river storm will bring multiple inches of precipitation to our mountains, much of that in the form of rain.  As rain falls on old snow and snow from the last 2 days, wet loose avalanches are expected to occur.  If snow levels fluctuate throughout the day, wet loose avalanches could happen quickly where any rain falls on new snow.  Most of these wet loose avalanches are expected to remain small in size, but some could some could be larger as the heavy rain weakens the snowpack.  Avoid steep slopes if it's raining or wet surface snow is forming. 

Avalanche Discussion

Our forecast region has been dealing with a shallow snowpack and limited terrain options for recreation.  One of the main hazards continues to be colliding with obstacles that are exposed or slightly buried under the recent snow.  Rocks, bushes, stumps, logs, and open water will be encountered if travelling in the backcountry currently.  An avalanche of any size would most likely involve hitting these obstacles and the chance for traumatic injuries.

Our shallow snowpack is highly variable with some complex layering at the higher elevations.  During the 3+ week dry spell in late November/early December the upper snowpack became weak and faceted.  Since then, recent storms have been warm and wet with high elevation rain.  Most of the snowpack below around 8500-9000' has been rained on with these faceted layers becoming wet and gaining strength.  At higher elevations above 9000', rain fell in most areas with thin rain crusts forming on the snow surface.  With less rain at some of these higher elevation areas, below the surface rain crust continues to exist weak dry faceted snow.  Due to our limited terrain available with snow, the same areas that folks will be going to recreate will be the same places where this weak snow exists.  This large current storm through Monday evening will test the weak layers in our snowpack.     

Regions covered