Bollettino valanghe

Gunnison

Crested Butte Avalanche Center
Vedi sulla mappa

Pericolo valanghe

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

In sintesi

There have been three people caught in wind slab avalanches in the past two days (Incident 1, Incident 2).  Even though we haven't seen measurable snowfall in a long time, conditions have changed since the green light jailbreak in January.  You are most likely to get surprised today by a thin but hard wind drift because wind slabs can break above you and may not give obvious warning signs.  In wind-sheltered northerly terrain where the snow surface is soft and sugary, expect to trigger sluffs or loose dry avalanches in steep terrain.   Both of these avalanche problems are small in size and fairly harmless by themselves unless they carry you into consequential terrain such as trees, over cliffs, or into gullies.   

Problemi valanghivi

  • 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 hard slabs up to 10" thick over weak faceted snow. The most common area to find this avalanche problem is near treeline on north to east facing slopes, where we saw the most widespread drifting on top of facet layers.  Drifted hard slabs can be lurking on some below treeline slopes where you find wind-affected snow.  Although drifting in the past week has been less common above treeline due to a lack of soft snow available for transport, expect to find isolated pockets of old hard drifts or some very shallow soft drifts involving last night's inch of new snow.    The problem appears on the surface as smooth, dense, lens-shaped snow deposits behind tree fences and on the lee sides of ridged terrain features. In some cases, multiple generations of wind slabs have formed, so reading textures may not be as reliable as simply recognizing suspect terrain features.     Collapses and shooting cracks are warning signs of the problem.

  • 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 problem is most common in sheltered terrain below treeline, but you can also trigger sluffs on some near treeline slopes and a few above treeline slopes.     

Avalanche Discussion

We have gone the entire winter season so far without any reported near misses or avalanche incidents.  Now, in the past two days, three people have been caught and carried in wind slab avalanches.    Conditions aren't especially dangerous, but they are clearly capable of producing surprises, especially because we are transitioning out of a prolonged period of Low danger.  

Our snow surfaces and shallow avalanche problems are caught in a battle between soft, recycled powder and firm, wind drifted slabs.  Wind has been gaining the upper hand in recent days.  The loose snow that was causing widespread sluffing on northerlies near and below treeline earlier this week has seen increasing amounts of wind mixing into those more protected slopes. This has made for a not-so-fun mix of stiff wind slabs scattered amongst loose or eroded snow surfaces.  We've painted the distribution roses to highlight where you are most likely to find each of the problems, but you can certainly expect to find a mix of both issues at all elevations, with problems more commonly found near and below treeline.   Instabilities appear to be more isolated above treeline where there has been less soft snow available for sluffing or wind transport this week.  However, we raised the danger to Moderate above treeline today to account for additional drifting last night and some uncertainty around our wind slab distribution.  

These problems are at the snow surface so by paying attention to surface textures and riding quality, you can identify concerning features.  If it's soft and cohesionless, congratulations: you've found sluff management, the easiest problem to identify and manage, and the best quality riding.  If it's firm and grabby, our sincere condolences: you've landed in wind slab territory, where avalanches can now break above you and will give less consistent feedback.   Our media gallery below shows what both of these issues look like.     

Regioni coperte