Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 7 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Although the odds of triggering an avalanche are decreasing with each day of dry weather, the consequences remain serious. If you find the wrong slope, you can bring down a large and dangerous avalanche that breaks several feet thick on old, weak layers.  Near and above treeline is most worrisome, especially on the colder aspects where snow surfaces are still powdery.  If you are traveling in steep terrain, choose slopes with deep, uniform snowpacks to reduce your risk.  Default to lower slope angles or terrain below 10,500' when in doubt.    

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Potential continues for human and remote-triggered slabs that fail 2 to 4 feet deep on depth hoar, facets, and faceted crusts.  Northerly and easterly facing terrain near and above treeline has been most active this month due to thicker slabs over well-developed weak layers. Cracking and collapsing are obvious signs of instability, although your first clear signal could be a dangerous avalanche due to variable and diminishing feedback.  In the Northwest Mountains, slabs are most likely to be triggered in terrain where slabs are thinner or variable in depth from wind effects. The most reliable way to manage this problem is by choosing slopes less than 30 degrees. Wind-protected southerly aspects and elevations below ~10,500' offer safer snowpacks, where slabs are less common and weak layers are often capped by stronger crusts. 

    A large persistent slab ran naturally on the west side of Mt. Baldy on Saturday.  

Avalanche Discussion

The good news is that human-triggered and natural persistent slab activity has paused since Saturday, and our last reports of collapses were on Sunday. This marks a gradual decline in danger compared to last week, when triggered avalanches and signs of instability were frequent. The bad news is that explosive mitigation results, recent stability tests, and poor snowpack structures continue to show the potential for large avalanches breaking several feet deep.

This is a common pattern during persistent slab cycles and one that has led to unfortunate surprises in the past—nearly 40% of fatal avalanches in Colorado occur during Moderate danger, most often involving persistent slabs. With each day of dry weather (and we have plenty ahead), more slopes transition from problematic to more reliable as the snowpack slowly adjusts. A good strategy right now is to begin with terrain that has forgiving consequences and where you have the highest confidence in the snowpack. Yesterday’s discussion highlights specific features of concern under the current setup. As the snowpack continues to evolve later this week and next, the odds will continue to shift more favorably toward safer travel.

Today, we lowered the danger to Low below treeline in the Southeast Mountains. In our shallow zone, thinner and softer slabs are the quickest to lose cohesion and stabilize, especially under strong inversions that are aggressively faceting the snowpack. Isolated exceptions exist toward the upper end of this elevation band (above ~10,500') where slabs are thicker, buried rain crusts are weaker, and inversion effects have been less pronounced. The danger increases to Moderate as you approach treeline, exemplified by yesterday’s observation on Mt. Emmons.  

Upcoming Outreach Events:  

Fireside Chat:  Jan 23 Dave Scheefer "Historical avalanches in Gunnison County."  CB Museum 5-7 pm

Trailhead Days: Jan 23 Slate River 10 am-2 pm

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