Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 10 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Moderate avalanche danger exists throughout the forecast area due to deep slab and wind slab avalanches.  Dangerous avalanche conditions continue to be possible with many deep slab avalanches occurring throughout the forecast area within the last 48 hours including a skier triggered deep slab avalanche in the Mt. Rose area yesterday partially burying a skier and a car.  Large avalanches with severe consequences could be human triggered today.   Cautious route finding and conservative decision making are essential.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3

    Many large and destructive deep slab avalanches have occurred in the last 48 hours.  The recent storm snow is settling and consolidating quickly with the weak and developed facets above the Dec. 15 rain crust adjusting to this large new load.  A skier triggered deep slab avalanche yesterday, snowpack tests, informal observations, whumpfing sounds and widespread cracking all indicate that this layer is still reactive.  Large, destructive, human triggered deep slab avalanches remain possible today throughout the entire forecast area on W-NW-N-NE-E aspects at all elevations.  These slabs could measure anywhere from 4 to 10+ feet deep.

    Deep slabs are unpredictable.  Remote triggering with large propagation into any connected terrain remains possible.  Large to historic runout zones could occur if a deep slab avalanche was triggered.  Ski tracks on a slope will not be an indicator of stability and steep trees will not be a safe zone.  Avalanche avoidance and cautious route finding remain the best practice to deal with this deep slab avalanche problem.

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2

    Wind slabs will continue to be a problem on NW-N-NE-E-SE and in some areas S aspects in near treeline and above treeline terrain.  Winds shifted briefly overnight to the NE and were strong in speed for several hours at the highest elevations.  Any wind slab development that occurred from these NE winds is expected to be small and limited to the highest ridgetops and peaks.  Winds have shifted back to the SW and will be light throughout the day.  Recently formed wind slabs will need time to adjust and gain strength.

    Look for cornice formation, snow surface scouring, and wind pillows to help identify areas where wind slabs have formed.  Use caution in these areas to avoid wind loaded terrain.

Avalanche Discussion

Observations were made and received from Jakes Peak (West Shore area), Silver Peak (Pole Creek area), and Fireplug (Mt. Rose area).  Yesterday on Fireplug, a skier triggered deep slab avalanche partially buried a skier and an automobile on the highway.  Minor injuries were reported but the party of 2 was able to self evacuate from the scene.  This avalanche was triggered mid slope and propagated away from the skier with crown lines up to 6 feet deep.  Deep slabs, wind slabs, and storm slabs were observed on Jakes Peak and Silver Peak.  Snowpack tests and informal observations showed that triggering a deep slab avalanche continues to be possible.  Deep slabs on Jakes and Silver Peaks were mid slope below treeline terrain around 35 degrees in steepness. 

Limited information has come in of a natural avalanche on Polaris Bowl in the Carson Pass area.  Crown was thought to be 5 to 6 feet deep, released mid slope, with a long runout.  This avalanche has very similar characteristics and thought to also be a deep slab avalanche. 

The deep slab avalanche problem has been observed throughout the entire forecast area and continues to be an ongoing issue. 

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