Avalanche forecast

Gunnison

Crested Butte Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

 This IS NOT the friendly snowpack we had in January.  Several large hard slab avalanches up to several feet thick were remotely triggered yesterday (See this video and this observation).  Three people have been caught in wind drifted slab avalanches since Thursday (Incident 1, Incident 2).  Stay off and away from drifted terrain features: they can break above you and some are large enough to bury you.    In wind-sheltered northerly terrain where the snow surface is soft and sugary, skiers and riders are still triggering loose dry avalanches in steep terrain.   All of these issues will be magnified if you get carried into a terrain trap.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Strong northwesterly winds have been raking the mountains and mixing into typically more sheltered locations over the past week.  Incremental wind drifting has built hard slabs ranging from just a few inches to several feet thick over weak facet layers.  We've seen the most significant wind loading and slab formation occurring at or just above treeline, especially in terrain with large fetches favored by northwest winds.   Slabs will not heal quickly because they formed over persistent weak layers, and they can be remotely triggered from below or adjacent to steep slopes where the drifted snow spans onto lower slope angles.   The problem is localized to leeward terrain features and most often appears on the surface as smooth, dense, lens-shaped deposits behind tree fences, on the lee sides of ridged terrain features, and in concave catchments such as gullies.   Collapses and shooting cracks are clear warning signs of the problem.  Give wind loaded terrain a wider berth than normal.

    The crown of a remotely triggered persistent slab in Cement Creek.  The avalanche broke up to 3 feet thick on faceted weak snow below. 

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    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

Surprises. Surprises. Surprises.  And not the fun kind like getting a Valentine from a secret admirer.

On Thursday, an experienced backcountry skier got surprised when he found an unstable wind drift in dense, normally protected trees. Turn the volume up on the video, you can hear the surprise in his voice right before he gets knocked off his feet. On Friday, a hard slab breaking on an unusually low angled slope surprised and caught a pair of veteran skiers while they were ascending what has been a regular uphill route all month.  And yesterday, our forecast team was surprised to see not one, but three triggered hard slabs large enough to bury or kill you, with crowns reaching 3 to 5 feet thick (Ob 1, Ob 2).  By now, it should be no surprise to anyone reading our forecasts that steady northwest winds in the past several weeks have spoiled our month-long streak of dealing with small and friendly avalanche problems in our backcountry.  However, you might also be surprised that, despite all of this talk of wind, people are still finding wind-protected snow and triggering long-running loose dry avalanches on a daily basis (Ob 1, Ob 2).

A few quick notes on our persistent slab problem and distribution - the problem formerly known as wind slab.  Although the issue is a bit of a hybrid right now, our travel advice is migrating more and more into the persistent slab category. Our forecasters have been covering a lot of ground with binos over the past few days to document how the wretched northwest winds have distributed slabs throughout the terrain.  It's fairly obvious that the near treeline elevation band is the goldilocks for catching the most wind loading, based on both recent avalanche activity and by reading loading patterns.  Winds were so strong and ravaging in the alpine that many of the classic alpine start zones are eroded; drifted slabs are more isolated throughout the terrain.  Winds didn't affect as much below treeline terrain, so slabs are smaller and less common below treeline.  Regardless, you can certainly find a hard slab at any elevation today and our travel advice is to remain cautious at all elevations.  Operating under the assumption that drifts were thin, we had expected the recent bouts of sun crusting between wind events to help with bonding on the more southerly aspects.  That doesn't appear to be the case now that we're seeing slabs several feet thick, evidenced by bulky slabs breaking on south and southeast aspects yesterday. I've updated the rose accordingly, and we'll continue to adjust the rose as conditions evolve and as our understanding of the situation improves with more data.  Use the rose as general guidance on where you are most likely to find slabs, but most importantly, read the local drifting patterns for each unique piece of terrain. This video gives some examples.  Terrain-specific drifting patterns have been quite variable; we have even seen a couple of slabs break on windward aspects that are scoured to dirt only a few feet higher on the slope.  

And now on to the good surprises.  Eric likes dark chocolate and Evan prefers the little heart-shaped candies like this one. Don't forget, tomorrow is the day.  

Regions covered