Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
1 · Debole
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 13 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Pockets of  MODERATE avalanche danger remain near and below treeline on NW-N-NE aspects on slopes steeper than 32 degrees where consistent snow cover exists. Lingering persistent slabs are keeping the possibility of human triggered avalanches ongoing in certain areas near treeline and below treeline on NW-N-NE aspects. For all other areas avalanche danger is either LOW or non-existent due to the lack of snow cover.

Problemi valanghivi

  • Deep Persistent Slabs

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

    Variability in avalanche danger exists around the forecast area. Persistent slabs linger in some areas near treeline and below treeline on NW-N-NE aspects due to the presence of the faceted Dec 7 persistent weak layer. Field observations of the past 3+ weeks have shown the greatest amount of ongoing instability with little to no week to week stability improvement in the Carson Pass and Pole Creek/Deep Creek areas. Observations from the Mount Rose, Donner Summit, West Shore Tahoe, and Echo Summit areas have shown significantly less ongiong instability and in some cases stable conditions near treeline and below treeline on NW-N-NE aspects.

    Triggering and going for a short ride in even a small avalanche at this time will almost certainly have significantly elevated consequences due to the almost guaranteed impact with rocks, logs, or trees due to the shallow snowpack. Becoming caught in the same size avalanche above a more typical deep Sierra snowpack could very well have minimal consequences.

Avalanche Discussion

Observations made just two days ago on Dec 31 showed significant ongoing snowpack instability in the Carson Pass area. Travel on near treeline and below treeline N-NE aspects in the area south of Red Lake produced cracking and collapsing of the snowpack. Some of the collapses occurred on the same slopes and areas previously collapsed by the same forecaster traveling through the area on Dec 12. Click here and watch the video showing very impressive collapse and propagation of the faceted Dec 7 persistent weak layer along a 2 meter (6.6ft) wide extended column test in this area just two days ago. It is an excellent illustrator of the ongoing snowpack instability.

Avalanche danger on SE-S-SW-W aspects has been mostly eliminated due to melt. Some snow cover exists on E aspects, but the Dec 7 facet layer has not been observed at any elevation on E aspects. The Dec 7 facet layer is also absent above treeline on NW-N-NE aspects. This is allowing for LOW avalanche danger in these areas. Near treeline and below treeline on NW-N-NE aspects, continued snowpack settlement has reduced the overall snowpack height and allowed rocks, logs, and stumps to show through the snowpack in places that were previously covered.

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