Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Mon
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Very dangerous avalanche conditions prevail for areas seeing active wind loading and the continued threat of large to very large natural avalanches. Northwesterly winds increase through the day, so be prepared for changing conditions, and make a plan to avoid traveling under potential overhead hazards. Increased winds will also penetrate lower elevations this afternoon and help create soft slabs in the low-density snow that fell yesterday. Careful snowpack evaluation and cautious route finding will be necessary, as soft slabs may become more reactive through the day. You can find a reduced avalanche hazard and good powder on some lower-angled southerly-facing slopes that lack wind-loaded terrain above. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    Storm totals on Saturday ranged from 15" to 25" of low-density snow. There is a large amount of snow available for transport by the wind. Northwesterly winds will increase throughout the day, thickening yesterday's soft slabs and adding significant load to wind-loaded terrain. There is a high likelihood of natural avalanches occurring below some ridgelines and cross-loaded terrain features. These avalanches could become larger than expected as they entrain additional volume as they descend through the terrain, or become very large if they steep down into deeper persistent weak layers. The best travel advice is to avoid traveling in wind-loaded terrain or under terrain that is experiencing active wind-loading. 

    This is an old photo of active wind-loading on Schuylkill Ridge. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3

    Yesterday's storm snow may become more reactive over persistent weak layers as it gains a little cohesion and better forms soft slabs. You will need to evaluate whether you are more likely to trigger sluffs or a soft slab. The old snow surface under the recent storm snow consists of facets, windboards, and a collapsible crusts. This varying snowpack structure will create inconsistent avalanche feedback from one slope to another or aspect to aspect. A triggered avalanche could further step down into deeper weak layers that had previously become dormant prior to the recent loading event. An avalanche on these deeper weak layers could become destructive and unsurvivable. The most reliable way to manage this problem is to choose slope angles less than 30 degrees with no overhead hazards.

    A pair of small soft slabs that gouged a few times into older weak snow, accumulated mass, and became large in size. Gothic Mountain, west aspect at 12,000ft. 1/24.

Avalanche Discussion

Storm totals vary widely from west to east across the forecast area. Official professional snow measurements are: Irwin 23" with 1.3" of SWE. CBMR 5" with .4" of SWE. While backcountry observations reported around a foot of new snow along the boundary of the two forecast areas, including Mt Emmons, the base of Coneys, and the north side of Snodgrass. Yesterdays avalanche observations included both natural and human triggered storm slab avalanches and many dry loose avalanches. 

Today, we separated out a wind slab avalanche problem, as wind-loaded terrain will become the most likely areas for both human triggering and natural avalanche activity. Yesterday's storm slab avalanche problem was combined with the old persistent slab avalanche problem. The new soft slabs may not exhibit obvious signs of instability until they gain more cohesion in the slab. That could occur as they begin to stiffen from the cold wind in open areas at lower elevations. 

Yesterday, observations revealed that we didn't hit HIGH avalanche danger at near treeline elevations in the northwest mountain forecast area. The avalanche danger was reevaluated and dropped to CONSIDERABLE today at that elevation band. Don't be misled by that drop; natural avalanches remain possible, and human triggering remains likely. HIGH avalanche danger has remained at above treeline elevations. As the wind increases later today, natural avalanche activity is expected. 

A non-avalanche-related topic: the very cold temperatures will make complex decision-making difficult. They will also complicate injuries and rescue. Set yourself up for success by planning in a warm environment, and spare yourself from difficult decisions when you are rushed by the cold. 

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