Bollettino valanghe

Central Sierra Nevada

Sierra Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Low avalanche danger will continue to exist throughout most of the day.  As the approaching winter storm impacts our region late this afternoon/evening, avalanche danger will begin to increase.  By this evening, considerable avalanche danger will exist.  Wind slab, storm slab, and persistent slab avalanche problems will become likely during the evening and overnight hours.  Natural avalanche activity is likely and dangerous avalanche conditions will exist.

Problemi valanghivi

  • Wind Slabs

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

    Strong to gale force SW winds along with rapid loading of new snow will quickly start building wind slabs late this afternoon.  Wind slabs will continue to build throughout the evening and overnight with natural wind slab avalanches likely.  These wind slabs are expected to be on NW-N-NE-E aspects in near and above treeline terrain.

    Look for blowing snow, new cornice formation, and wind pillows as clues to where wind slabs are forming.  Avoid steep wind loaded terrain.

  • Loose Dry

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

    Storm slabs will be likely on all aspects in near and below treeline terrain.  These storm slabs could have weakness within the new storm snow or at the old snow/new snow interface. 

    Look for cracking around skis, shooting cracks, or any signs of cohesion within the new storm snow.  Avoid areas that show signs of unstable snow.

  • Deep Persistent Slabs

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

    Persistent slabs will become possible on NW-N-NE aspects in isolated areas in near treeline and below treeline terrain.  This weak layer remains active in isolated areas throughout the forecast region.  Concern exists that this layer could fail with a large load of new snow.  Any avalanche due to this persistent slab avalanche problem would have elevated consequences due to increased slab size involved. 

    Look for collapsing, cracking, and whumpfing sounds.  Remote triggering is possible, along with failure mid to low slope.  Avoid steep avalanche terrain and runout zones where this problem may exist. 

Avalanche Discussion

* Unstable test results reported in near and below treeline terrain on the buried facet layer over the last week.  Other locations are showing this layer and the overall snowpack gaining strength including Slab Cliffs (Mt. Rose area) and Waterhouse Peak (Luthur Pass area) yesterday.

* 1 natural triggered persistent slab avalanche on Jan. 11 reported.  No human triggered avalanches reported on this weak layer.

* 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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