Bulletin d’avalanche

Central Sierra Nevada

Sierra Avalanche Center
Voir sur la carte

Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
Open full map
Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Additional avalanches were reported yesterday. Areas of unstable snow are expected again today with another round of snow and wind. Consider avoiding slopes adjacent to recent avalanches, areas where wind drifted snow has been deposited,  slopes below cornice features, or any avalanche terrain where snow surface cracking is occurring.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Additional wind slab avalanches were reported yesterday in near treeline and above treeline areas.  A 180 degree wind shift along with additional snowfall will make it possible to encounter a wind slab on just about any aspect today. It could be a wind slab that formed under SW winds over the past two days or a new wind slab that formed after last night's wind shift to the NE and E. Wind slabs may also exist to a lesser extent in below treeline areas near ridgelines where drifting of snow has occurred.

    Identify and consider avoiding the avalanche terrain where wind drifted snow has deposited as a thick wind slab. Large avalanches could be triggered today, especially on open slopes below cornices and cliff bands. In addition to recent avalanches, snow surface cracking triggered while making new tracks in the snow is a sign of instability and a signal to pull back from avalanche terrain.

    (1/15/2023)

    Intentionally triggered wind slab avalanche, south of Webber Lake, near Little Truckee Summit, CA.

    Photo: Public

  • Storm Slabs

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

    Additional reports of storm slab avalanches were received yesterday from wind protected terrain below treeline.  Additional storm slabs and weak layers within the new snow may form today, especially in the southern half to third of the forecast area where the highest snowfall rates and overall accumulation are expected today. Lingering unstable storm slabs formed Saturday and Saturday night may remain in all portions of the forecast area.

    If there are signs of recent avalanches in the area, snow surface cracking is occurring, or test slopes are failing, pull back from avalanche terrain and onto sub 30 degree slopes without steeper terrain above.

    (1/15/2023)

    Natural avalanche on NE aspect terrain around 7,800', Mt. Tallac, CA.

    Photo: Public

Avalanche Discussion

There are numerous rain crusts buried in the snowpack that could have small amounts of faceting around them due to melt layer recrystallization. Some of these crusts are now buried 8 to 17 feet deep in the snowpack making them very difficult to assess with snowpit tests. The vast majority of avalanches at this time are expected to occur much higher in the snowpack. An isolated avalanche event up to D4 in size that fails on a crust deep in the snowpack would not be a major surprise during or immediately after this storm cycle. It would be impressive, but not a representation of the vast majority of expected avalanche activity.

Recent Observations

  • Size D1 and D2 wind slab and storm slab avalanches failing within the top 3 feet of the snowpack occurred both Saturday and Sunday along with other signs of instability including snow surface cracking.

Régions couvertes