Bollettino valanghe

Gunnison

Crested Butte Avalanche Center
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Pericolo valanghe

Sat
Alta quota
1 · Debole
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

In wind-sheltered areas, your primary avalanche concern is sluffing or loose dry avalanches. While in wind-affected areas you could find hard wind slabs 1 to 8 inches thick. Both of these avalanche problems are small in size and fairly harmless by themselves. Your terrain selection is what will magnify these avalanche problems. In long-running steep terrain, a small avalanche could accumulate additional mass. Or a small avalanche could be enough to push you into a tree or off a cliff, and lead to a higher consequence outcome. Yesterday a skier was taken off their feet by a thin wind slab, before arresting on the bed surface.  That avalanche continued to run 800ft through trees in steep terrain. 

Problemi valanghivi

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    Dry loose avalanches (sluffs) are a concern in wind-sheltered terrain on the north half of the compass.  Where the snow surface is weak and cohesionless, you can easily trigger sluffs that entrain the top 6" to 10" of loose snow on slopes steeper than 35 degrees. Ski cuts, moving across the fall-line while descending, or choosing lower-angled slopes are effective techniques to manage this problem. These point-release avalanches will accumulate more mass in long-running, steep terrain. Use caution above gullies where an avalanche can pile more deeply and above trees and cliffs where the consequences of getting caught in a small sluff will be magnified. This avalanche problem becomes isolated at near and above treeline elevations where snow surfaces are commonly affected by previous winds. 

    A great example of sluff management in terrain where a loose dry avalanche could be more problematic because it gets funneled down a gulley.  

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Northerly and westerly winds this week have been mixing into typically more sheltered locations and finding some snow to blow around. The result has been the formation of thin hard slabs, 1 to 8" thick on average, over weak faceted snow. The most common area to find this avalanche problem would be the near treeline elevation band. Some open below treeline slopes may also be suspect where you find wind-affected snow. This avalanche problem is the most isolated in distribution at above treeline elevations where there was little snow available to blow into new slabs. These hard wind slabs can primarily be identified by smooth, lens-shaped snow deposits behind tree fences and on the lee sides of ridged terrain features. 

    A small wind slab located in an uncommon forested area and below a stand of trees. Note how the skis are riding up onto this hard lens-shaped wind slab before it releases. 

Avalanche Discussion

We are seeing some interesting conditions this winter. There has been very little new snow since the start of January. The last avalanche that was large in size was explosively triggered on January 10th. With the lack of a large avalanche problem, backcountry riders have been pushing aggressive terrain options for some time now. In recent weeks, loose dry avalanches became a common avalanche problem at all elevations as the snow surface has become weak and faceted during this drought. Now the last several wind events have changed those conditions. The wind has been wrecking above treeline elevations for some time now. So it's difficult to find soft snow surfaces at above treeline elevations where sluffs could be a problem. Given the lack of soft snow surfaces in the alpine, there has also been little snow available for transport into wind slabs. Given that avalanche problems are very isolated at this elevation band, the avalanche danger has remained at level 1. 

This week we have seen wind events mix into the near and below treeline elevation bands. In those areas, we have started to see the elimination of the loose snow avalanche problem in many areas where snow surfaces have become wind affected. While in others we have observed those soft snow surfaces add fuel for new wind slab formation. The travel advice for both wind slabs and loose snow avalanches applies for both of these elevations bands, while it would be most common to encounter an old wind slab at near treeline elevations and a loose snow avalanche at below treeline elevations. 

For the record, I think I used the words "wind event" like 5 times in this discussion, and the words "snow storm" 0 times. 

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