Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Fri
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

An AVALANCHE WARNING is in effect.  Very dangerous avalanche conditions exist at higher elevations.  A natural avalanche cycle is underway.  Remote triggers and surprisingly wide avalanches are back on the menu.  Our well-advertised January weak layers will be producing many avalanches today at all elevations to both human and natural triggers.  We recommend enjoying all of the new snow on low-angle terrain without overhead hazards.  

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2.5

    Snowfall and windloading this week are forming slabs over the fragile facets and faceted crusts that formed during our long drought.  Anticipate unusual and challenging behavior associated with these recently buried persistent weak layers, such as remote triggering and surprisingly wide propagation.  Even relatively thin slabs can grow to large sizes on the north half of the compass where they entrain the old, weak snow below (See video).  Shooting cracks and collapsing are clear warning signs of the problem.  There is isolated potential for slabs in the upper snowpack to step down into older weak layers near the ground, producing a deeper and larger avalanche.   You can reliably avoid today's problems by traveling on slope angles that are consistently less than 30 degrees in steepness without overhead hazards.  

    This photo illustrates the remote triggering potential for avalanches that fail on weak facets or faceted crusts.  

Avalanche Discussion

Our fieldwork yesterday in a snow-favored corner of the deep zone is scary foreshadowing for what we'll see across our entire forecast area as today's storm totals launch our developing persistent slab problem into action.   Yesterday, we remotely triggered slides from as far as 1000' feet away on the treacherous weak layers that have been getting slowly buried this week.  Now, as snowfall intensity ramps up, slabs are thickening and becoming more continuous across the terrain.  Slabs are thickest on wind loaded terrain, but they now extend into many wind-sheltered slopes, which is where our weak layers are most fragile and capable of significant entrainment.  We expect a natural avalanche cycle is underway on many slopes today, especially in the snow-favored Northwest Mountains.  The destructive potential is bordering our criteria for High danger (Level 4) in the Northwest Mountains; with the potential for unusually wide slides and significant entrainment of old snow, we're going to fall on the Level 4 side of the fence this morning.    In the big picture, the Northwest Mountains have seen almost 3" of SWE on our January weak layers, and the major overnight pulse (up to 14") along with alpine winds gusting into the 60's will make avalanche terrain a scary option today that is best avoided.  The Southeast Mountains have seen about a third of the loading on our January weak layers, so slabs aren't as large or widespread yet.  Avalanche conditions are still quite dangerous.   In the snow-starved areas, slabs will be shallower and more predictable below treeline, but if you're on the north half of the compass, expect significant entrainment. Small rolling terrain features away from terrain traps can offer some lower-risk options below treeline.  Slopes less than 30 degrees are the most reliable way to play in the snow today.   

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