Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Heightened avalanche conditions exist at mid and upper elevations, where stubborn, persistent slabs are primarily found on previously wind-loaded slopes. A few human-triggered slab avalanches occurred yesterday, two in Upper Cement Creek and one to the north of our area near Aspen. Easterly and southerly-facing slopes received the most wind loading last week, while the avalanche problem has a more isolated distribution on other aspects. In wind-sheltered areas, northerly-facing slopes offer soft riding conditions, where small dry loose avalanches are the primary concern in steep terrain.

Problemi valanghivi

  • Loose Dry

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

    The upper snowpack is losing strength and has begun to sluff on steep slopes. This small avalanche problem is the most common at lower elevations, where the cold valley inversions have created the weakest snowpack. Most of these triggered avalanches will be relatively harmless, but where they run through sustained steep terrain, they can become larger in size and push you into more hazardous terrain features, such as trees, or pile deeply in terrain traps. 

    A small dry loose avalanche near Peanut Lake. 1/30.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Most avalanche concerns today involve slabs of drifted snow that formed over the facets and faceted crusts from our January drought.  These slabs, typically less than 2 feet thick, could remain sensitive to human triggers on some leeward terrain features, most commonly on east to south-facing aspects at higher elevations and on crossloaded features elsewhere.  Because these recent slabs formed on highly variable snow surfaces, expect hit-or-miss feedback as you move through the terrain.  Collapses and shooting cracks are clear red flags. There is isolated potential for a slab failing in the upper snowpack to step down and trigger a deeper, harder avalanche near the ground. Searching for wind-eroded and soft wind-dappled snow will help reduce your exposure to this avalanche problem, while the best way to avoid it is by riding in wind-sheltered areas. 

     

    A hard, persistent slab that was human-triggered in Upper Cement Creek on Saturday. This slab formed on the lee side of the ridgeline. 

     

Avalanche Discussion

The best riding and softest powder can be found on northerly facing wind-sheltered terrain at lower elevations. Given the reduced avalanche hazard here, this is a good time to get out and enjoy the backcountry in those areas. Small loose dry avalanches are starting to creep into the problem list as the snowpack loses strength in these wind-sheltered areas. These sluffs are the most common in the SE Mountain forecast area, where the snowpack is thinner. In the NW Mountain forecast area, the upper snowpack is still holding some cohesion, helping to hold back these sluffs. Exceptions exist in the NW Mountain forecast where the snowpack is below average in depth, like on an old avalanche bed surface. There, small sluffs will be more common, and conditions will be similar to the SE Mountain forecast area.

The persistent slab avalanche problem was primarily formed during a northwesterly wind event on Sunday, 1/25. The sensitivity of this avalanche problem trended down over the following week, and now it has become stubborn to trigger. Often requiring heavier loads, or light loads in just the right location. Weak layers are fairly common across the forecast area, while slabs above those weak layers are often more specifically located in previously wind-loaded terrain. The avalanche activity rose highlights this pattern of increased avalanche activity on wind-drifted easterly and southerly terrain.  You should expect to find drifted slabs on westerly and northerly aspects, but less frequently, and often due to crossloading. This video shares more information about the concerning structure Zach encountered in Rock Creek while investigating a natural avalanche.

If high temperatures are warm enough to produce wet loose avalanches on steep southerly facing slopes, that could lead to some interesting conditions where a small loose avalanche could trigger an old slab avalanche. This scenario has a very low likelihood, given that high temperatures at 11,000ft should only reach up to 36 to 41 degrees, and snow surfaces are often firm in exposed areas after last week's wind event. 

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