Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Stiff, possibly unstable slabs of wind-blown snow still exist near ridges and in gullies. The sun and warmer air may also cause wet snow to slide down steep slopes at lower elevations. Watch for changing conditions and any signs of unstable snow, like recent avalanches, cracks in the snow, roller balls, or pinwheels. Be willing to move into gentler terrain if there is doubt about the snow's stability.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    The slabs of wind-drifted snow on SE-S-SW-W-NW-N aspects near and above treeline have gained strength and gotten more difficult for people to trigger. That being said, people triggered cracking in some wind-loaded areas yesterday. It may still be possible for a person to trigger an avalanche involving these dense, hard slabs if they hit a spot where the slab is thinner or softer (trigger points) today. Exposed slopes near ridges will hold wind slabs, with complex terrain around cliffs where an unsupported wind slab lurks or couloirs where conditions may be more variable, representing the most suspect terrain. 

    These slabs will look smooth and filled-in, feel firm on the surface, and may sound hollow underneath. Look for signs of instability like cracking or unstable test results on small test slopes or on the edges of these slabs where they might be thinner. If signs of instability or uncertainty about a slope exist, move away from that area. Traveling in terrain sheltered from the wind can help bypass potentially unstable wind slabs and locate more consistent snow conditions.  

    (1/31/2023)

    Hard wind slab up to 8'' deep. These did not extend very far downslope and were only reactive when the underside of slab was cut on Incline Lake Peak.

    Photo: SAC

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Sunshine and warmer weather today may create enough wet snow on sunny slopes for a wet loose avalanche to occur. Places near sunny rocks and trees will experience the most warming. Most of the wet loose avalanches would remain small due to the shallowness of the recent snow, but long steep slopes can produce larger wet loose avalanches since they gather more snow as they move downhill.

    Look for signs of unstable wet snow like rollerballs, pinwheels, or sticky wet snow. Once these start to happen, it is time to avoid steep slopes and move into lower-angle terrain.

Avalanche Discussion

  • Skier-triggered cracking and small wind slab failures occurred on small test slopes loaded by the NE and E winds yesterday. These were more stubborn than they were on Monday, and many of them only cracked after they were undercut and kicked several times. 
  • While buried surface hoar exists under the recent storm snow in some areas, very little snow exists above this surface hoar and observations have not found signs of storm slab instability. 
  • Widespread wind-affected snow exists in open areas near and above treeline. 
  • Warming temperatures today will change the snow surface, and some wet snow may form, especially on sunny slopes. 

Régions couvertes