Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Mon
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Out of date — this forecast expired 3 years ago.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

Santa teased us yesterday with a skunk and then pulled through with storm totals in the 4" to 8" range. That new snow has added volume for loose snow avalanches and created the potential to encounter a small storm slab avalanche problem. A triggered avalanche could further step down to deeper weak layers and become larger than expected. Enjoy the little bit of new snow, the riding conditions may be better than you expected. If you find yourself uncertain about the avalanche problems, defer to simpler and low-consequence terrain. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Since Friday evening, 4" to 8" of snow has accumulated. These small soft slabs will be possible to trigger where they have formed over weak snow. Those near-surface facets and surface hoar weak layers primarily existed on the northern half of the compass. Northwesterly winds have also formed small wind slabs on the lee sides of terrain features at upper elevations. To encounter this avalanche problem, you will likely need to be in areas that have the higher end of snow totals, the weakest old snow surfaces, and/or additional wind-loading. There is a remote possibility that an avalanche triggered in the new snow, could further step down into the persistent slab avalanche problem and become larger than expected. 

    A small soft slab that was triggered on Saturday 12/23. 

  • Persistent Slabs

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

    Slabs 1 to 3 feet thick exist over several persistent weak layers in the snowpack:  Weak facets and depth hoar near the ground and surface hoar layers in the upper snowpack. The problem was most common on northerly and easterly facing slopes earlier this month, along with some wind-loaded westerly facing terrain. After below-average snowfall for the last two weeks, these weak layers are expected to be temporarily dormant on most slopes, with the potential for isolated exceptions from the small amount of loading this weekend. The most suspect areas could be, extreme terrain, unsupported slopes, or previously wind-loaded terrain features. You can reduce your risk by traveling on south-facing slopes that have thick crusts, or by traveling on smaller terrain features without terrain traps.  You can avoid the problem on slopes consistently less than 30 degrees. 

    This large persistent slab was triggered by skiers descending the ridgeline on the Aspen side of the Elk Mountains last weekend, 12/17.  

Avalanche Discussion

In the Northwest Mountains, a weather station near Irwin and another in the upper Slate River drainage, are both showing storm totals near 8". Other weather stations are showing lower totals around 4". Over in the SE Mountains, storm totals only reached 3" and I suspect 4" exists somewhere. Wind speeds yesterday afternoon at 12,000ft, increased with averages in the teens and gusts into the 20's and 30's from the west to northwest. Overnight wind speeds remained generally light. SWE totals at Schofield Pass are .4", Lake Irwin .75" and Butte .3". That water weight isn't a significant load for the persistent slab avalanche problem. However, it is another loading test and we will be keeping our eye open for any surprises. The best guess would be an avalanche that releases where the 12/7 interface exists as buried surface hoar. 

Forecasted winds may increase at upper elevations tonight, and this will be something to keep an eye on for tomorrow. Wind speeds look to increase again later on Monday. Other than any potential wind-loading, there are no other weather factors driving the avalanche danger as we head into the start of next week. 

This video highlights some of the avalanche terrain that is on the naughty list vs the nice list. 

 

Avalanche Beacon Park Update:

Want to practice your avalanche beacon skills over the holidays? A practice area is currently set up behind the community school (located here). The control box that runs the normal park is out for repairs, but in the meantime, there are two beacons buried in the training park. Get out there and get some practice over the holiday!

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