Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
1 · Debole
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A shallow and generally weak snowpack structure continues across the forecast region.  The persistent slab and wind slab avalanche problems have become unlikely on a regional scale.  LOW avalanche danger exists at all elevations.

Problemi valanghivi

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2

    The forecast area has a generally shallow, weak, and highly variable snowpack.  The Dec. 11 persistent weak layer has been gaining strength over time and adjusting to the recent storm snow load on top of it.  Overall, there has been a lack of avalanche activity associated with the Dec 11 weak layer with no reported avalanches in over 5 days.  Signs of instability and unstable snowpack test results have been on the decline for multiple days as well.  All of our data points to this avalanche problem becoming unlikely on a regional scale.  The process of this weak layer gaining strength and rounding will take time and may not occur at the same pace at all locations.   

    Whumpfing sounds, cracking, and/or unstable snowpack test results could indicate that this weak layer is still active in your specific area.  Limit exposure to avalanche terrain by having a trip plan, traveling 1 at a time through avalanche terrain, and regrouping well out of run out zones and avalanche terrain.     

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1

    Monday nights strong to gale force SW winds moved snow on to NW-N-NE-E-SE aspects creating small stiff wind slabs in near and above treeline areas.  Reports of minor cracking and a small natural wind slab avalanche were reported yesterday.  Winds shifted to the NE last night and increased into the strong to gale force range.  This will further scour exposed terrain and potentially transport some snow over to SE-S-SW-W aspects.  Limited available snow for transport exists in most areas with many firm and scoured areas potentially causing travel concerns and fall hazards.  Wind slabs are expected to continue to gain strength today with any avalanches expected to be small, D1 in size.  However, in complex terrain, even small avalanches could have increased consequences with secondary exposure and thin snowpack conditions. 

Avalanche Discussion

*  A small wind slab avalanche was reported from Stevens Peak, in the Carson Pass area.  3 to 4'' thick wind slabs were found in this area with some minor cracking.  Firm wind scoured  snow surfaces were found in near and above treeline areas.

*  Small stiff wind slabs 3 to 4'' thick were also found on Lincoln Ridge at Yuba Pass.  These wind slabs showed minor cracking but were not reactive with dropping cornice chunks on top.  

*  Signs of instability and unstable snowpack test results have been on the decrease for several days on the Dec 11 persistent weak layer.  Spatial variability continues throughout the forecast area with some areas still reporting unstable snowpack test results.   

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