Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Hochgebirge
1 · Gering
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
Veraltet — dieser Lagebericht ist 13 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

MODERATE avalanche danger still exists near and below treeline on NW-N-NE aspects on slopes steeper than 32 degrees where consistent snow cover exists due to lingering persistent slab instability.

Human triggered avalanches remain possible.

Brandon will update the advisory again in 2014 on Jan. 2 at 7:00 am.

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2

    In general if a NW-N-NE aspect has enough snow to recreate on, then human triggered persistent slab avalanches remain possible. Even though these kind of avalanches have become unlikely on some slopes, most sheltered near and below treeline areas with consistent snow cover still hold a slab sitting on top of a fragile weak layer waiting for the right trigger to break it loose. Areas where a shallower snowpack exists or trigger points like shallowly buried rocks represent the most likely places to trigger an avalanche. Trying to find these trigger points on a snow covered open slope would be quite difficult without x-ray vision.

    The increase in variability and uncertainty associated with the persistent slabs makes accessing snowpack stability difficult. Even though most observations may point to a stable slope, it only takes finding that one hidden trigger point to start a failure that could take down the whole slope. Using the terrain to avoid the avalanche hazard by recreating on lower angle slopes that remain disconnected from steeper and deeper terrain represents a fun and safe plan when conditions like this exist.

    Between the lingering persistent slabs and the shallow snow cover over rocks, logs, and other objects, significant hazards exist in the backcountry.

Avalanche Discussion

Yesterday on Mt. Judah (more info, snowpit, photo) observations did not reveal any signs of instability. The Dec. 7th facets still remain in the lower half of the snowpack, but tests indicated that a fracture traveling through this persistent weak layer has become unlikely. No human-triggered collapsing or cracking occurred in this area either. Unfortunately, significant melting had also taken place here exposing many more rocks and patches of bare ground on all aspects. Finding a place with consistent and continuous snow cover large enough to make more than 5 turns has become challenging in this area.

Yesterday's observation from Mt. Judah represents one of the few showing no signs of instability since Dec. 7th. Since that time 25 out of 30 observations have shown unstable results. Since Dec. 25, 4 out of 6 observations have shown unstable results. Data does seem to indicate that the snowpack has begun to gain some strength, but this process is very slow. Overall observations show a snowpack whose stability or instability varies greatly from slope to slope or even across an individual slope, and that stability or instability has become difficult to access.

Abgedeckte Regionen