Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Storm instabilities are improving after an onslaught of natural avalanche activity on Saturday.  The threat of triggering a large avalanche is most concerning in very steep or heavily drifted terrain features, or where the snowpack was unusually shallow prior to the storm.  Collapses or shooting cracks are clear warning signs to stay off of steep terrain.  

Avalanche problems

  • Storm Slabs

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

    The weekend storm delivered up 3 feet of mostly dense snow accompanied by periods of strong west/southwest winds.  The storm produced widespread natural storm slab avalanches on Saturday,  many of which were large enough to bury you.  Now, those slabs are bonding and becoming stubborn.  You are most likely to trigger a lingering instability up to several feet thick in terrain that is very steep (more than about 45 degrees) or unsupported, especially where winds have drifted the snow.  Consider terrain characteristics and consequences before riding in avalanche terrain.    The last 4" to 8" of storm snow is lower density and will be easier to trigger as shallow sluffs or thin slabs.

    This avalanche is an example of terrain characteristics that are most concerning today: The slope is wind-loaded, very steep, and unsupported by the rollover below the crown.

Avalanche Discussion

We're emerging from one of the more potent storms of the winter, which delivered 2.5" to 3.5" of snow water equivalent across our forecast area, the bulk of which fell from Friday afternoon to Saturday morning.  If this storm came in December on our typical spread of early-season weak layers, we would have seen widespread persistent slab activity and dangerous conditions lingering for several days or more after the storm.  Thankfully, our March snowpack is unusually deep and strong (Gunnison River Basin is at 148% of the median), and most of our terrain lacks well-developed weak layers.   This Cascade-style storm produced a widespread but shortlived avalanche cycle on Saturday morning, predominantly involving storm slabs breaking within the storm snow.  These issues tend to heal up after a few days, and we're seeing the avalanche danger trend down accordingly.  Storm slabs are expected to be stubborn today.  The last 4" to 8" of snow is low density and will easily sluff underfoot or shed naturally today with solar input, whereas the rest of the storm snow will be difficult to trigger in all but the steepest and most unsupported terrain.  

This weekend's system brought an impressive amount of snow to areas that are typically snow-starved, such as CB South and Almont.  These areas have a shallow and weaker snowpack that will be slower to heal after the storm.  This video from yesterday describes the setup.  If you find yourself thinking "Wow, that terrain barely had enough snow to ski all winter, but look how fat it is now!", that should alert you to the threat of triggering a newly developing persistent slab.   Faceted layers that formed during our dry spells in January and February are weakest towards the most southern portions of our forecast area, where snow depths have remained shallower all winter.  These avalanches (Ex A, Ex B) from just south of our forecast boundaries demonstrate the widely propagating behavior often associated with persistent slabs.  These concerns, or a thicker variation of them, span into our Southeast Mountains forecast area.  An observer in East Brush Creek on Saturday noted several storm slab avalanches that stepped down into deeper weak layers.   Long story short, the snowpack becomes more complex with a higher potential for triggering a persistent slab the further south and east you go in our forecast area, especially on drifted slopes. 

Events:  The Al Johnson race is Sunday, March 19. Information and registration are here.  Day of race registration and bib pick up 9-11 a.m. at the Adventure Center in Mountaineer Square. Proceeds go to the CBAC.

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