Avalanche forecast

Gunnison

Crested Butte Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

The areas that are most suspect for triggering a slab avalanche exist on previously wind-loaded terrain. These slabs are growing old and may require just the right trigger point to release, but the resulting avalanche can still be significant. Be aware that previous wind-loading also occurred down at some lower valley elevations, like this old human-triggered avalanche in the Slate River Valley. Seek out softer, wind-protected snow in sheltered terrain for better riding conditions and a lower chance of triggering a slab avalanche.  You'll have to manage for gouging point-release avalanches on slopes that roll steeply to around 40°, and they might grow larger than expected as they entrain the weak snowpack.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Slabs up to several feet thick are becoming increasingly isolated and difficult to trigger but remain a concern on some steep slopes facing west, north, east, or on wind-loaded southerly slopes.  You are unlikely to see signs of instability before triggering an avalanche that breaks on old weak layers.  Previously wind drifted terrain appears to be the most problematic, especially where slabs are thin near their margins, convexities, or rocky areas. You can reliably avoid the problem on slope angles less than 30 degrees without steeper slopes above you, and most wind-protected terrain lacks the problem.  

    This persistent slab was pried out by an explosive in the Irwin Guides Tenure on 1/27. 

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    You can easily trigger gouging  "facet sluffs" on some very steep (~40° ) slopes that are protected from the sun and wind.  You're most likely to encounter the problem in start zones that have avalanched multiple times this season and have an unusually shallow and weak snowpack (<50 cm).  These avalanches release predictably and start small, but can grow to harmful sizes in long relief or if they push you into trees or gullies.  Use defensive or off-fall-line riding techniques to manage the problem, or move to lower slope angles to avoid the problem.  

    A debris pile from loose dry avalanches accumulating in a gully below the Climax Chutes. 

Avalanche Discussion

Slab avalanches are becoming tired, lethargic, and more difficult to trigger, but by no means have they been put to bed. All of the slab activity last week was in wind-affected terrain. These occurred following a strong westerly to northerly wind event that occurred between January 17th and January 23rd. As these slabs continue to age, weak layers will slowly adjust to their load, but given the persistent grains in those weak layers, we are not even close to moving beyond the thread of more persistent slab avalanche activity. These slabs may take multiple tracks on the slope to find the right trigger point or somewhere that the slab thins and the weight of a rider can more easily affect the buried weak layer. Another reason that we may have observed a downtrend in slab avalanche activity is that the most worrisome terrain for triggering a slab avalanche has stiffer, more wind-affected snow, which isn't all that attractive to ride.  Our forecast team was targeting slab concerns last weekend, resulting in a remotely triggered avalanche on a small drifted slope and finding several propagating test results on buried weak layers  (video from Mt. Emmons, video from Schuylkill Ridge). These results highlight the continued potential for human triggering, which likely requires hitting the wrong spot (probably a thin area) on the wrong slope (probably a previously drifted slope where slabs are stiffer). 

The dry loose (or "facet sluff") problem is a good candidate for catching someone off guard.  Most lower-angle terrain has a deeper, stronger snowpack that doesn't feel sluffy or rotten.  It's not until you drop into a steep start zone, one that has avalanched a couple of times this season, that you encounter a thin and cohesionless snowpack.  Even then, there is sometimes enough wind effect on the snow surface to keep the issue at bay (Ex. A, B).  However, the evidence is clear that once you find that wind-protected snow surface and get the snow moving, it will entrain a significant volume and can pack a serious punch, easily large enough to drag you through trees (See recent avalanches here or a video of the problems here and here).  

 

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