Boletín de aludes

Northwest Mountains

Crested Butte Avalanche Center
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Peligro de aludes

Thu
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
Bajo el límite
4 · Fuerte
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

An AVALANCHE WARNING is in effect.  Heavy snowfall and strong winds are overloading a very fragile weak layer.    A large natural avalanche cycle is underway.  There were dozens of natural and triggered avalanches observed yesterday, and conditions are only getting worse as destructive sizes increase today.  You can easily trigger avalanches from below steep terrain, or they can release naturally from above you. Travel on or below avalanche terrain is not recommended.  Stay off and out from under slopes steeper than about 30 degrees.  

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Certain
    Tamaño
    1.5–3

    Natural and human-triggered slabs breaking several feet thick are almost certain today.  2 to 3 feet of new snow and strong winds have formed touchy slabs on top of exceptionally fragile facets and faceted crusts.  The avalanches can be triggered from below steep slopes, they can propagate surprisingly wide distances, and they can fail spontaneously.  There was plenty of evidence of this problem yesterday, and it has only grown larger and more dangerous in size today.  Choose slopes that are consistently less than about 30 degrees that don't connect to steeper terrain above you.  

    This slab failed on a collapsible crust yesterday and propagated 1500 feet wide.  

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    With heavy snowfall and windloading today, avalanches breaking on layers within the storm snow are a common threat.  In most terrain, slabs breaking within the storm snow will immediately step down to release a persistent slab that fails on the dry spell weak layer a few feet down.  On south to southwest aspects, the step-down and unusual slab behavior is less likely, so you'll be managing for storm slabs running on crusts or on layers within the storm snow.   Cracking and heavy snowfall rates are red flags for this problem.

Avalanche Discussion

Yesterday, we received a bunch of great observations highlighting dangerous conditions in the backcountry. See the gallery below or our observations page. There were numerous small to large avalanches breaking on the well-advertised weak layer that formed during our 6-week dry spell.  One propagated over a quarter-mile wide. One ran far and snapped trees in its runout.  And many of them were remotely triggered from adjacent flat terrain.  Continued snowfall and windloading overnight and today will only make things worse.  Storm totals are surpassing 30" in favored areas near Paradise Divide, and about half that in terrain closer to town.  With slabs growing thicker and denser, you can expect them to behave more erratically: anticipate wider propagation, longer remote triggers, slabs breaking into lower slope angles, and running longer distances.  Yes, persistent slabs are back on the menu, and they are growing to dangerous sizes and are touchy to human and natural triggers today.  It's a great day to ride the resort if you aren't comfortable identifying and avoiding avalanche terrain.  

We've painted HIGH danger across the entire forecast region today. The biggest difference between the two forecast zones today is avalanche size.  There is about twice the volume in the Northwest Mountains, and a few of the largest paths are capable of producing D3s today.  Slab sizes are about half as thick in the Southeast Mountains, and some of the least-favored parts of our forecast area will likely stay closer to Considerable danger below treeline because slab sizes are below size thresholds.  The sensitivity to triggers is bad everywhere. 

With the storm tapering tomorrow, we'll see natural activity decreasing while human triggering will remain very sensitive.   

 

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