Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Tue
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

The snowpack will remain generally safe provided today's storm totals don't exceed about 4".  Although it has become very unlikely, we can't rule out the potential to trigger a slab avalanche several feet thick on slopes that didn't avalanche during our previous cycle.  Guard against surprises with sound travel habits and use caution on intact slopes with variable slab thickness.  Manage for shallow new snow instabilities and facet sluffing in extreme terrain.  

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–2

    Our region experienced a widespread avalanche cycle on November 26-27. On slopes that survived the cycle, slabs have now settled to 1 to 3 feet thick over faceted snow that formed earlier this winter. In the dry weather since, the snowpack structure is gaining strength,  and the problem has become isolated and difficult to trigger. Any surprises are most likely found on wind-drifted slopes with variable thickness facing west, north, or east.   Slopes with consistently deep and uniform snowpacks or slopes that naturally avalanched last week offer lower-risk options for steep terrain on those aspects.  Move to smaller, less consequential terrain features when in doubt.  

    The last persistent slab triggered in the Northwest Mountains was this remotely triggered persistent slab on a west-facing slope above the Slate River on 11/28. This slope survived the natural cycle and had the necessary ingredients: a cohesive slab over weak, early-season snow.

Avalanche Discussion

A few inches of new snow today will have minimal effects on the avalanche danger.   If snowfall exceeds the forecast, stay alert for thin wind slabs forming below alpine ridges and expect the facet sluffs on shady aspects to gain a bit more volume. These issues will be small and easy to manage with defensive ski cuts but should be considered if you are in high-consequence terrain.  Increasing winds tonight and tomorrow may increase the hazard of fresh wind slabs at upper elevations, especially if the Ruby Range snow belt pulls out more than a few inches from today's snowfall.  

Almost two weeks of dry weather has allowed the snowpack to adjust from the major loading event just before Thanksgiving.  In the snow-favored Northwest Mountains, we continue to find evidence that most slopes with persistent slab structures naturally avalanched, and those that didn't are gaining strength.  This month, the lack of persistent slab avalanches or collapses in the Northwest Mountains illustrates the situation well.  However, recent propagating pit results at Irwin and Purple Ridge targeting those intact slopes are good reminders that we still have isolated persistent slab concerns.   

As you move east of Crested Butte, our limited observations demonstrate a less extensive cleanse from the natural cycle and a thinner snowpack that is somewhat slower to heal.  We've observed a few natural persistent slabs that likely ran a few days after the storm from wind drifting, and explosives or snowcats have triggered a few persistent slabs in the past week.  Although the likelihood of triggering a persistent slab is also decreasing now in the Southeast Mountains, we recommend a more cautious approach in wind-drifted terrain near and above treeline on slopes that didn't avalanche during the cycle. In most sheltered areas, the slabs have faceted away, leaving a stable snowpack except for shallow facet sluffs.    

Thank you to everyone who volunteered, supported, or attended Avalanche Awareness Night and Beacon Brushup this weekend.  We're thrilled to see such great community support and engagement!  

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