Lawinenlagebericht

Northwest Mountains

Crested Butte Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

As new snow accumulates throughout the day, it will add volume for loose snow avalanches in steep terrain, and slightly increase the chance for slab avalanches releasing on persistent weak layers deeper in the snowpack. Keep an eye out for changing conditions throughout the day, and on how much snow accumulates in the area you are traveling.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    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 has been most common on northerly and easterly facing slopes earlier this month, along with some wind-loaded westerly facing terrain. After the recent dry spell, these weak layers appear to have become temporarily dormant.

    Slab avalanches will become more likely this weekend in areas that see new snow accumulations of around 6" or more. Those slabs could release at the old snow surface or 1 to 3 feet deep on older weak layers. Once an avalanche initiates, it could gouge to the ground and become much larger than expected. 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

Come on Santa! We are really hoping for some snow out of this storm before the sky clears on Christmas Day. The current snow forecast will not add a notable load to the snowpack. So the most notable changes will be a little more snow available for entrainment in loose snow avalanches, and a slight increase in the chance for persistent slab avalanches to release on weak layers in the upper snowpack. The avalanche danger has increased to MODERATE as backcountry travelers will need to evaluate both the snow and terrain carefully, to identify the potential changing conditions. Provided we get enough snow out of this storm, this video highlights the terrain that is on the naughty list, vs the terrain on the nice list. 

This video highlights the expected changing conditions if we get enough snow out of this storm. 

Observers on Thursday reported "facet sluffs" in the Climax Chutes, and this is a great example of the current loose snow avalanche problem. The old snow surface is weak after the prolonged dry spell, and where there isn't a crust at the snow surface, that weak snow is available for entrainment.

Last week, explosive testing of poor structures in both forecast zones continues to suggest that more slopes have become dormant due to the recent dry spell.  Dormant means that weak layers are not healed but have reached equilibrium under current conditions.  With additional loading, we expect our buried weak layers (such as the 12/7 surface hoar layer and 11/16 depth hoar layer) to become more reactive. That additional loading is something we need to keep an eye on this weekend as new snow accumulates. The layers of buried surface hoar will likely be the first interface to become more reactive. A threshold of around 6" or more of new snow, will likely need to be met before we start seeing changes. 

 

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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