Lawinenlagebericht

Central Sierra Nevada

Sierra Avalanche Center
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Lawinengefahr

Hochgebirge
1 · Gering
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 11 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

LOW avalanche danger exists on all elevations and aspects today. Some unstable snow could exist on isolated terrain features. As the next storm impacts the region tonight and tomorrow expect the avalanche danger to increase quickly.

Lawinenprobleme

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    0

    Even though the winds will increase today, wind slab formation should remain limited due to the lack of snow available for transport on the sun crusted and wind scoured windward aspects. Other than some minor wind transport, today's warm temperatures, increased cloud cover, and possible light rain could allow some small loose wet instabilities like sluffs, roller balls, or pinwheels to form as well.  Both the loose wet snow and the isolated wind slabs should remain small.

    Even though avalanche activity has become unlikely, backcountry travelers should still practice safe travel techniques like traveling one at a time in avalanche terrain, regrouping safe spots out of the avalanche paths, avoiding travel near terrain traps, and practicing good communication within your group. Small avalanches can still occur in isolated areas or extreme terrain during LOW avalanche danger. 

Avalanche Discussion

Observations from Donner Peak, Castle Peak, and Rubicon Peak found soft snow on northerly aspects yesterday. On Castle Peak observers reported some minor sluffing with no other signs of instability. Snowpit data and general observations from Donner Peak and Rubicon Peak also did not find any signs of instabilities. On Rubicon Peak snowpit work did identify the remains of a buried surface hoar layer, but this layer has rounded, become much stronger, and mostly assimilated into the snowpack. Tests targeting this layer also did not show any signs of lingering weakness.  

What happened to the deep persistent weak layer?

In early to mid January, up to 3 separate surface hoar layers formed and were buried by subsequent storms on N-NE-E aspects near treeline and below treeline.  These buried surface hoar layers are currently buried 1.5 to 4.5 feet deep in the snowpack.  A widespread persistent slab avalanche cycle occurred Jan 5 through Jan 19 on these weak layers.  Many slopes have been "cleaned out" by already avalanching, or the surface hoar has been collapsed or compressed and has gained strength.  Targeted observations and snowpack tests have shown that these layers, in the majority of locations, are no longer reactive and have assimilated into the snowpack.  No avalanche activity has been associated with these buried surface hoar layers since Jan. 19.

This deep persistent avalanche problem has become unlikely and has been removed as an avalanche problem.

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