Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A trace to a few inches of new snow over the next 24 hours will simply help keep snow surfaces soft. While the primary avalanche problem will see little day-to-day change. Continue to practice good travel habits such as riding one at a time through avalanche terrain, and managing the persistent slab problem through your terrain choices. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Slabs 1 to 4 feet thick have formed over several persistent weak layers in the snowpack:  Weak facets near the ground and surface hoar layers in the upper snowpack. The problem has been most active on northerly and easterly facing slopes, with some avalanches on westerly facing terrain as well. Persistent slabs are gradually becoming more difficult to trigger and signs of instability are becoming less frequent, but if you cross the wrong slope or the wrong spot on a slope, a single collapse can result in a surprisingly large avalanche involving most of the snowpack.  Persistent slabs could break wider than you expect, and they can be triggered from flat slopes connected to steeper terrain above you. You can reduce your risk by traveling on slopes where the problem isn't highlighted above, or by traveling on small terrain features without terrain traps.  You can avoid the problem on slopes consistently less than 30 degrees.    

    A natural avalanche on an east-facing slope of Treasury Mtn into North Pole Basin. Debris spilled over and triggered another avalanche on the north-facing slope below the cliffs.  Likely ran 12/10.  

Avalanche Discussion

Back around December 4th, we were recording avalanches left and right, with numbers well into the triple digits. Since early December, we have observed a major decline in avalanche activity with the last few avalanches having occurred on December 10th. The avalanche danger ratings during this time have also slowly declined to where we are now. The strong over weak persistent slab structure is still there, but without major loading events, the weak snow is better at tolerating the burden of snow it is holding, or in some cases, the weak snow is slowly healing. This is causing a decline in how reactive the avalanche problem is. Early-season trends in Crested Butte are often the same as what we are currently experiencing. If your happy place involves riding low-consequence terrain, well you are in luck because in many areas that low-angle snow is riding well. Stepping out in your terrain choices is also fair, given the decreasing chance of triggering an avalanche. We must always remind you that persistent slabs are notorious for their deceptive behavior. As Zach wrote yesterday, "Your assessments should include more than just 'Can I trigger it?' You need to also ask yourself, 'Do I have uncertainty?' and 'What are the consequences if my assessments are wrong?". 

In the SE Mountain Forcast area, the avalanche danger rating for the below treeline elevation band was dropped to LOW. Many low-elevation slopes in this forecast area lack enough snowpack to produce an avalanche, while on those that do, this assessment is a bit more involved. The last documented avalanche, below treeline in this area, was a D1 on December 8th. The snowpack structure remains poor in areas highlighted by the persistent slab problem rose, and isolated columns in snowpack tests continue to highlight that poor structure. However looking bigger picture to slope scale and beyond, the avalanche problem has trended to isolated and stubborn or even dormant. Normal caution is advised while using good travel habits such as riding one at a time through avalanche terrain. Avalanche forecasters have been hunting for areas where the avalanche problem could remain reactive, and those potentially more reactive areas have included previously wind-loaded terrain at these lower elevations and areas right along the forecast boundaries between the NW and SE forecast areas. 

Regions covered