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 9 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Avalanche danger is LOW for all elevations. On a regional scale, triggering an avalanche has become unlikely. Localized, isolated areas of instability may still exist where a human triggered persistent slab or wind slab avalanche could occur. Identify the specific avalanche problem that may exist in the desired area of travel and take appropriate steps to manage it.

Problemi valanghivi

  • Deep Persistent Slabs

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

    Below treeline and near treeline terrain that is above 8,200' on NW-N-NE-E aspects is where any lingering persistent slab instability is most likely to exist. Faceted snow that is generally found 6 inches to 2 feet below the snow surface has become wet in some areas but remains dry to moist in other areas, especially around 9,000' and above. Open areas below treeline and near treeline with good protection from NE winds is where the facets had become weakest prior to the last round of storms. These same areas are the focus of lingering concern for this avalanche problem.

    Keep in mind that triggering of a persistent slab avalanche could very well occur on the mid or lower portion of the slope, rather than near the top like a wind slab avalanche.  

  • Wind Slabs

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

    Ridgetop winds out of the SW were strong in speed yesterday afternoon and last night. Small wind slabs may exist near and above treeline today on NW-N-NE-E-SE aspects. As winds shift to the NE tonight, redistribution of snow on the ground could create more small wind slab formation on SE-S-SW-W-NW aspects.

    Look for clues such as recent cornice formation, wind pillows, and snow surface sculpting that identify areas of recently drifted snow and the potential location of this avalanche problem. Take appropriate steps to manage any areas of suspected wind slab.

Avalanche Discussion

* Observations made yesterday specifically targeting faceted snow layers of the persistent slab avalanche problem on Red lake Peak (Carson Pass area) and on Rubicon Peak and Peak 9,269' (West Shore Tahoe area) indicated improving strength of the snowpack in the areas traveled.

*  Consistent unstable snowpit test results were observed Wednesday on Tamarack Peak (Mt. Rose area) on a buried layer of facets.  These observations were made on NW-N aspects in near treeline and below treeline terrain.

*  On Tuesday, a naturally triggered persistent slab avalanche occurred on Elephants Hump in the Carson Pass area.  Widespread signs of instability with collapsing, cracking, and whumpfing of the snowpack were also observed near and below treeline on N-NE-E aspects on Elephants Hump that day.

* NW-N-NE aspects above 8,000' in the Mt. Rose area and along the Sierra Crest north of Emerald Bay hold the best coverage at 2 to 4+ feet. Overall less snow cover exists south of Emerald Bay. Areas of decent coverage exist above 8,300' on NW-N-NE aspects in the Carson Pass area.  Coverage decreases dramatically on all other aspects.

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