Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A large avalanche was explosively triggered in the Kebler Pass area yesterday and serves as a reminder of the sizable avalanches that remain possible to trigger today. Don't expect to receive any obvious warning signs from this avalanche problem to alert you of its presence. Consider riding in simple terrain where it is easier to manage a complex avalanche problem. The cold weather and occasional light snow showers have preserved some good riding conditions on lower elevation southerly facing slopes that will also offer the safest avalanche conditions. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    Slabs averaging 2 to 3 feet thick in sheltered terrain and larger in wind-loaded terrain can be triggered where they formed over well-developed facets and collapsible crusts on west, north, and east aspects. Additionally, wind-loaded slabs could fail above buried crusts on high elevation, southerly aspects.  Relatively shallow slopes (<120cm)  and terrain features where slabs get thinner are most problematic.  Slab behavior is challenging with variable and deceptive feedback, remote triggering potential, and wide propagation across terrain features.  You can reliably avoid the problem on slope angles less than 30 degrees without steeper slopes above you, and most mid to low-elevation southerly aspects lack the problem.  

Avalanche Discussion

4 long weeks! That is how long it has been since the last time we saw MODERATE avalanche danger show up in the avalanche forecast. The avalanche danger is slowly easing as a few changes occur in the snowpack. Let's look at the extreme ends of the spectrum where persistent slab avalanches have become less likely to trigger, and then those Goldilocks slopes that remain the most concerning. Where the snowpack is shallow, the cold weather has begun to facet away the slab. As those slabs break down, they are not as capable of propagating an avalanche through the terrain. Where the snowpack is deep, weak layers in the middle of the snowpack have had enough time to gain some strength, becoming less sensitive to triggering or requiring a thin trigger point to initiate a collapse. The Goldilocks slopes are likely going to be somewhere between ~90cm and ~120cm, where slabs remain intact and weak layers have not gained much strength. The total snow depth is extremely variable across the forecast area, largely due to all the avalanche activity that has occurred this winter. In general, lower-angled slopes tend to be deeper, and steep start zones tend to be shallower. 

The avalanche danger has remained elevated the longest in the Southeast Mountain Forcast area. This is due to two reasons. The total snowpack depth is more commonly the ideal depth for continued avalanche activity, and a natural avalanche cycle ended just last Sunday. The Northwest Mountains didn't see the same type of natural avalanche cycle last weekend, and we mostly observed small storm slab releases after 8" to 18" of snow accumulated on Saturday, with a few large avalanches like these on Mt Baldy. In either forecast area, the snowpack is still very capable of producing large and deadly avalanches. This fact will not go away any time soon. Avalanche conditions will remain complicated. When avalanche conditions are complex, the terrain is the answer. So, consider avoiding the avalanche problem or riding in simpler terrain where the avalanche problem will be easier to manage. 

Events:  Our next Fireside Chat is this Thursday, 7 p.m., at the billy barr lounge, where Danielle Beamer will discuss Mental Health and Backcountry Decisions.  The event is free and open to all.  

Régions couvertes