Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

The snowpack is teetering - dangerous avalanches are easy to trigger today.  An AVALANCHE WATCH is in effect in anticipation of another avalanche cycle and HIGH danger starting by tonight.   The threat of large natural avalanches will be increasing later today with winds revamping ahead of tonight's system.     Our snowpack is dangerous and challenging: we saw a widespread cycle of avalanches breaking near the ground over the weekend and two more fatalities occurred in Colorado yesterday.  Triggered or natural avalanches today can break wider than expected and run long distances.  Cautious routefinding and conservative decision making are essential.  You can safely enjoy the powder on slope angles less than 30 degrees that don't undercut steeper terrain above.  

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    Dangerous persistent slab avalanches have been releasing naturally all week.   Avalanches are breaking 2 to 6+ feet thick, across entire start zones and producing destructive amounts of debris in their runouts. You can trigger avalanches while traveling on or below steep terrain.  They can also release naturally from windloading or snowfall.   The best way to reliably manage this problem is by traveling on slopes less than 30 degrees that don't connect to steeper terrain above.  Avalanche activity has been most common on the eastern half of the compass at all elevations, but you can trigger an avalanche on any aspect and elevation.  

    Several destructive persistent slabs that broke on weak layers near the ground this weekend on Mt. Whetstone

Avalanche Discussion

The firework show continues around Crested Butte.  Since Thursday, we have documented 96 slab avalanches failing on all aspects of the compass - most of them were large enough to bury or kill you.  We've cherry-picked our favorite photos from the weekend cycle in the gallery below, and our observations page documents the rest. The bulk of activity ran between Friday and Saturday night, with some avalanches continuing to release yesterday (watch this video, see this ob).   Avalanches are breaking on buried crusts and facets that formed during our prolonged dry spells in early December and early January.  On below treeline slopes close to town, crowns are about two feet thick.  Moving to higher elevations or deeper parts of the forecast area, crowns are up to six feet thick or more and capable of snapping trees or reaching far into their runouts.    

Make note that while this cycle was ongoing, we received several observations of "spooky quiet" and "no signs of instability" or often just one or two ground-shaking collapses.  Direct feedback underfoot becomes less common as weak layers get buried deeper, but the lack of feedback is not a ticket to ride steep terrain right now.  Buried weak layers are clearly teetering under prolonged stress over the past few weeks, and all it takes is hitting the wrong spot on the slope for the walls to come crashing down, or just enough wind or snowloading to do the same naturally.   Both fatalities yesterday  (one near Loveland Pass and the other near Rollins Pass) exemplify this frightening reality.  

Winds are forecast to increase to moderate speeds today ahead of the next system.  Winds have been spurring persistent slab activity all season.  Natural activity will be on the rise today, depending on how strong winds show up.  Avoid traveling on or below leeward terrain, including the runouts down at low elevations where you might not feel any wind.  Expect the danger to reach HIGH tonight.  

Régions couvertes