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

Blowing and drifting snow will deposit in lee areas forming unstable wind slabs above treeline and near treeline. Areas of unstable snow may form in wind protected areas near treeline and below treeline during the late day hours, possibly sooner. MODERATE avalanche danger exists above treeline and near treeline. LOW avalanche danger below treeline early this morning will increase to MODERATE danger as the day progresses.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Strong to gale force SW winds blowing and drifting new and old snow in above treeline and near treeline terrain is expected to form cohesive slabs in lee areas. These wind slabs will be most prominent on wind loaded and cross loaded NW-N-NE-E-SE aspects. The depth of wind slabs and the potential size of avalanches will increase today and tonight. The expected avalanche size will increase from D1 to D2 during the day today.

    Areas where drifting snow is depositing below cornices and cliff bands or where depositing into drifted pillows are suspect. Identify where wind slabs likely exist and move around them with caution.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Storm slabs failing at the old/new snow interface in wind protected areas near and below treeline will become possible either late this afternoon or tonight. Graupel and on some northerly aspects surface hoar at the old/new snow interface may allow for storm slab instability to begin to show once new snow amounts exceed about 4 inches. As new snow amounts increase more rapidly after 4 pm, storm slabs will become more of an issue. If the upper end of forecast snowfall amounts is reached earlier today, this avalanche problem will develop sooner. Expected avalanche size will start at D1 today, potentially increasing to D2 near sunset or later on tonight depending on snowfall rates.

    Snow surface cracking created while breaking trail in wind protected areas below treeline is a sign of unstable storm slabs in the area.

Avalanche Discussion

* No new deep slab avalanches have been reported in the past two days with snowpit data showing significant strength gains at the weak layer interface.

* Breakable to semi-supportable sun crusts at the old snow surface are widespread across most aspects with the exception being northerly aspects above about 7,600'.

* Graupel has been observed at the old/new snow interface for the start of this storm and may contribute to instability. On some northerly aspects, this graupel is also mixed with surface hoar creating the potential for an even more problematic weak layer at the old/new snow interface.

Regions covered