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 avalanche danger exists throughout the forecast area due to persistent slab and wind slab avalanche problems.  Human triggered avalanches are possible today.  Persistent slab avalanches will be possible at all elevations and wind slab avalanches will be possible in near and above treeline terrain.  Heightened avalanche conditions exist on specific terrain features.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Persistent slab avalanches will continue to be possible on NW-N-NE-E aspects at all elevations.  A natural persistent slab avalanche occurred yesterday at 8400' on a North aspect in the Carson Pass area.  Widespread signs of instability also existed in the area with cracking, collapsing, and whumpfing of the snowpack.  Terrain near treeline and below treeline seem the most likely areas for the combination of weak faceted layer and overlying slab to exist.  These persistent slabs could exhibit wet slab characteristics in areas below 8500' to 9000' due to recent rain and warm temperatures.  In most areas, the facet layer is moist to wet and is expected to gain strength once the snowpack refreezes.  But at this point, the weak layer has a large load of heavy wet snow on top and is continuing to be reactive.

    Look for collapsing, cracking, or whumpfing of the snowpack.  Start zones could be low or mid slope in near treeline or below treeline terrain.  Practice safe travel protocols and avoid avalanche run out zones.  These avalanches are capable of injuring or burying a backcountry user.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Small wind slab development was observed yesterday.  West winds will increase today and will have the potential to form new wind slabs in near and above treeline terrain.  These wind slabs are expected to be small at elevations below 8500'.  Where more snow is available for wind transport, wind slabs could be larger and add to existing wind slabs that formed yesterday in areas above 9000'.

    Look for blowing snow, cornice formation, wind pillows, in areas along ridgelines and wind exposed terrain.  Avoid steep wind loaded terrain.

Avalanche Discussion

*  Natural triggered persistent slab avalanche on Elephants Hump in the Carson Pass area.  Widespread signs of instability with collapsing, cracking, and whumpfing of the snowpack.

*  Facet layer is moist to wet in most areas below 9000'. 

*  2 to 3'' of new snow in the Tamarack Peak (Mt. Rose area).  Wet snow conditions existed below 9300'.  Small wind slabs were triggered off of ridgeline.

* NW-N-NE aspects above 8,000' in the Mt. Rose area and along the Sierra Crest north of Emerald Bay hold the best snow coverage at 2 to 3+ feet. Overall less snow cover exists south of Emerald Bay. Areas of decent coverage exist above 8,500' on NW-N-NE aspects in the Carson Pass area.  Coverage decreases on all other aspects. Large areas of bare ground exist on the vast majority of southerly aspects at all elevations.

Regions covered