Boletín de aludes

San Francisco Peaks / Kachina Peaks Wilderness

Kachina Peaks Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Backcountry travelers may trigger wind slab avalanches on all elevations near and above treeline especially where newly deposited windpockets have developed.  The San Francisco Peaks were battered last week by high winds with wind board, wind stripped areas, hardened wind slabs and sun crusts dominating most upper elevations.  Moderate to high winds on Sunday and in addition to small amounts of snow transported yesterday  could create soft wind pockets releasing with the weight of a single skier/rider.  The potential to trigger a large deep persistent slab avalanche in loaded areas on north and northeast slopes remains a possibility.  

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    On many east, south and west aspects a sun crust has developed.  Transported snow from yesterday's winds and today's small amount of new snow could create soft wind slabs that may not adhere to the new sun and wind effected surface.  In these newly wind loaded areas small avalanches could be triggered by skiers and riders.  These wind slabs will likely be small but could carry an individual over steep or rocky terrain.  Be able to identify these locations if you choose to travel in complex wind effected areas, such as steep chutes and at the top of avalanche paths.  In isolated locations hard wind slabs from last week's wind event will continue to be incrementally loaded.  

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1–2.5

    Some starting zones on north and northeast slopes will be additionally loaded by the incoming storm and wind transport.  In wind loaded locations, basal facets may be stressed by this added weight.  Recent observations indicate that the presence of this weak layer, found deep below the snowpack at ground level, is diminishing.  However, the distrubition of this problem may vary significantly, even in adjacent locations.  While triggering a slide of this type will be unlikely, the consequences will be severe.  An added issue is that in some circumstances a wind slab release could step down and trigger this persistent weak layer.  The only way to determine the presence of this problem is to examine the snowpack, and in many loaded areas this could create a dangerous situation.  Do not assume that avalanches will not occur under the weight of single skier.  Use caution and continue to avoid these heavily loaded starting zones.

Avalanche Discussion

Light winds yesterday transported additional snow.  This in combination with the newly developed sun crust creates the possibility of increased soft wind slab.  These newly formed wind slabs will be more reactive, and although they are likely to be isolated and small, they need to be noted and avoided.  If triggered above terrain traps, such as rocks and cliffs, they could carry a skier over consequential features.  Be on the look out for cracking and whumphing, obvious signs of instability.

High velocity winds from nearly all directions hammered  the upper elevations of the San Francisco Peaks last Monday thru Thursday.  Friday and Saturday afforded a respite from this large-scale wind event, but the upper elevation terrain has been highly wind effected.  Wind board and scoured slopes were present on almost all aspects and elevations, and the current storm has deposited light snow on this new surface or on sun crusts that developed over the weekend.

A few slopes received additional loading by west and southwest winds.  These winds continued to load common starting zones.  The extent of the deep slab problem remains hard to assess due to access and the number of slide paths, but the possibility of this further loading producing ideal conditions for a deep slab avalanche continues.

With a myriad of snow surfaces across the San Francisco peaks the extent of bonding on these new layers is uncertain.  Bring additional awareness when traveling deep into the backcountry due to the wide range of conditions.

On west, north, and east slopes a buried layer of near surface facets exists between the old and new storm layers.  This layer produced fracture planes in compression tests in multiple locations over the last few days; however, the upper layer of snow remains unconsolidated, meaning that propagation is unlikely.  This weak layer could become problematic if loaded by snow from yesterday and today's storm. 

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