Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Alpin
1 · Faible
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 11 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Pockets of Moderate avalanche danger exists on N-NE-E-SE aspects near treeline and below treeline due to the Jan 5 buried surface hoar layer.  Persistant slabs are possible today in terrain where this weak layer occurs.  In areas where this weak layer is absent, Low avalanche danger exists.  Evaluate snow and terrain carefully, identify features of concern.

 

Problèmes avalancheux

  • Deep Persistent Slabs

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

    The Jan 5 buried surface hoar layer is down 1-1.5' deep in the snowpack and has been reactive since last Tuesday.  Snowpack tests continue to show that this layer has not stabilized and that propagation is possible.  The areas of concern are N-NE-E and possibly SE aspects near treeline and below treeline in open but protected terrain.

    The Jan 5 buried surface hoar layer does not exist everywhere and is not a common problem for our area.  This problem will be limited to near and below treeline terrain, not the upper elevation avalanche starts zones that we normally deal with.  Use careful terrain selection to avoid steep, open slopes near and below treeline.  Use proper travel techniques to help limit the risk for you and your group.

Avalanche Discussion

Observations from Deep Creek (Cabin Creek area) showed the presence of the 1/5 buried surface hoar layer.  In some places this layer was not reactive and in others it showed consistent results with snowpack tests that propagation is still possible.  Other observations from Carpenter Ridge (Independence Lake area) and Mt. Judah (Donner Summit area) did not find the 1/5 buried surface hoar layer present.  Where this layer is not found, the snowpack is well bonded and consolidated with no signs of instability.

The Jan 5 buried surface hoar layer is known to exist in various areas on Donner Summit, Deep Creek, and some areas on Carson Pass.  It has not been observed at Barker Pass (Blackwood Canyon area), Echo Peak (Echo Summit area), Jakes Peak (West Shore area), and Mt. Tallac (Desolation Wilderness area).

The last avalanche activity associated with this weak layer was last Thursday on Andesite Peak (Donner Summit area) and Thursday and Friday on Red Lake Peak (Carson Pass area).  These avalanches were human triggered, 1-1.5' deep, and occurred on NE-E aspects near treeline and below treeline.

 

Régions couvertes