Boletín de aludes

Northwest Mountains

Crested Butte Avalanche Center
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Peligro de aludes

Sat
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

New and drifting snow will increase the avalanche danger through the day.  Avalanche conditions are expected to become dangerous at high elevations by late afternoon or evening.  The most problematic terrain continues to be mid and upper-elevation slopes that face northwest to east, where persistent slabs up to several feet thick are sensitive to human triggers and the increasing threat of naturals.  Monitor for changing conditions and shallow instabilities in the new snow elsewhere.  

Problemas de aludes

  • Persistent Slabs

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

    Each of our past two storms has caused a clear pattern of natural and human-triggered persistent slab avalanches on the north half of the compass near and above treeline.  Accumulating and drifting snow will gradually increase the sensitivity of the problem today, and we could start to see some natural activity by sunset.  Slabs are typically 1 to 3 feet thick and have the potential to break wider than you might expect, or can be triggered from flat slopes below steep terrain.  In terrain harboring a stiff slab over faceted weak layers, be cautious of slopes steeper than about 30 degrees.  Shooting cracks or collapses are a clear sign of danger.  Slopes below about 10,500' and southerly-facing terrain currently lack the problematic structure and offer lower risk options today.   

    One of many large persistent slabs that failed naturally during last weekend's storm.  Similar, albeit larger, activity is expected this weekend.

Avalanche Discussion

The danger is on the rise as a winter storm starts to impact the region today and intensifies through the weekend.  We've bumped the danger to Considerable above treeline in the Northwest Mountains, where forecasted storm totals and wind speeds by sunset are flirting with crossing into dangerous territory and the potential for large naturals.  If not by sunset today, we'll certainly be there tomorrow.   Only a few inches or less in the Southeast Mountains today will keep conditions fairly stagnant for one more day before the danger rating is expected to increase tomorrow.  

If you are storm-riding the worrisome northerly or easterly aspects today, monitor for changing conditions.  In steep, low-elevation terrain, you may encounter shallow instabilities in the new snow that entrain old, weak snow and grow larger than expected.  As you gain elevation above about 10,500', the snowpack starts to gain enough "slabbiness" or cohesion to cause persistent slab failures on the weak snow near the ground.  Cracking or collapsing will be an obvious signal of this transition, or you'll at least notice a more supportive snowpack underfoot.  Eric's observation from Purple Palace demonstrates this transition to where the sharks start to circle.   Climb higher into wind loaded terrain, and the sharks get larger and more irritable, especially as fresh wind drifting stacks up later this afternoon.  

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