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

MODERATE danger will quickly form on slopes steeper than 35 degrees on all aspects and elevations starting in the mid morning hours with the E-SE-S-SW aspects that receive morning sun. This warming should continue onto the W-NW-N-NE aspects during the day. Loose wet avalanches large enough to threaten backcountry travelers will be possible again today. Evaluate snow and terrain carefully. Identify and avoid the areas where wet snow deep enough for loose wet avalanches exists. 

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Warmer overnight lows that remained well above freezing in most areas and some scattered thin cloud cover will mean that any refreeze that did occur as a result of radiational cooling last night will be weak and thin at best. Today's warm temperatures and plentiful morning sunshine will quickly melt through this weak refreeze. In addition to these warming influences, some afternoon cloud cover may help distribute the warmth to all aspects. Once the refreeze melts, the ice bonds that give the snowpack strength will have melted away leaving deep loose weak wet snow in many areas. Loose wet avalanches will become possible on slopes steeper than 35 degrees wherever loose wet snow exists. Loose wet activity will become possible on the E-SE-S-SW-W aspects at all elevations first and then progress to the NW-N-NE aspects as they warm up a little later. Most of the wet snow instabilities should manifest as loose wet avalanches but other forms of wet snow instabilities like glide cracks or wet slabs are not impossible. 

    Once last night's melt-freeze crust starts to become unsupportable and the wet snow starts to deepen, it becomes unstable very quickly. In the last few days the snowpack has become unsupportable in many areas before noon. As soon as the snowpack starts becoming unsupportable, it is time to move to more frozen aspects, onto lower angle slopes away from anything steep, or to trade boots for flip-flops and head for an afternoon activity that does not involve snow.

    Stepping off your equipment and sinking into wet snow above your boot tops and small surface instabilities like roller balls, pinwheels, or point releases can provide clues that enough wet snow has formed for larger loose wet avalanches to become an issue. Terrain traps like gullies, creeks, and cliffs can greatly increase the risk of any size loose wet avalanches.

Avalanche Discussion

This week's observations have shown melt-freeze conditions on all aspects and elevations that start out frozen in the morning and quickly soften as the day warms up. The first slopes to soften in the mid morning hours are the E-SE-S aspects followed by the SW and W aspects. These slopes have held the most well developed melt-freeze crusts and corn snow conditions. The sun-exposed northerly aspects have soften slightly slower often waiting till late morning. On these northerly aspects transitional snow still exists below the melt freeze crusts. Several loose wet avalanches of various sizes have been reported this week as well as a few isolated larger wet snow instabilities like a wet slab and some glide cracks when the snow pack did not refreeze early in the week. 

Regions covered