Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Thu
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

Avalanche conditions are generally safe.  Warming temperatures and sunshine may create small wet snow avalanches by the afternoon.  Monitor surface wetness on steep, sunbaked slopes, particularly near rocky areas where the snow surface may warm the most.  An outside chance exists for you to trigger a slab avalanche on the north half of the compass on slopes with an abnormally shallow snowpack or in extreme terrain.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    In the Northwest Mountains, high-consequence slabs breaking on older weak layers have become isolated and difficult to trigger. Any lingering persistent slabs are most likely triggered from an unusually shallow or previously wind-eroded slope where the total snowpack height is below average.  Large cornice falls could act as triggers as well. Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.  The most problematic structures are on shallower slopes on the north half of the compass.  Mid to low-elevation, southerly aspects have the most trustworthy snowpack.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem when in doubt.  

    The crown of a very large persistent slab remotely triggered by snowmobiles on March 8.  This slope is west facing and eroded by seasonal winds, making for a shallower and more problematic snowpack than other slopes. 

Avalanche Discussion

The Persistent Slab problem is the primary issue on Wednesday.  Recent avalanche activity and observations suggest that shallower snowpacks on the north half of the compass represent the most likely place for you to trigger a dangerous slab avalanche.  You are more likely to encounter a shallow snowpack in the Southeast Mountains, but a thin snowpack can still be found in isolated places in the Northwest Mountains.  A recent natural avalanche in Terminator Chutes on Saturday and a triggered avalanche resulting in a very close call near Snowmass on Monday highlight the issue.  Both of these avalanches occurred in terrain with shallower snowpack due to less seasonal snowfall and/or previous wind erosion.  You can reduce your risk of triggering a slab avalanche by traveling where the snowpack is consistently deeper than 200cm (~ 6 feet) and by avoiding terrain with obvious trigger points.

Wet snow concerns exist in both forecast zones due to seasonally warm temperatures and sunshine.  Wet avalanche problems are expected to remain small with this observation from Monday illustrating the current character.  A few places could produce natural sluffs today; very rocky areas are warmer than open slopes and the lowest elevation sunny slopes where warmer temperatures more effectively wet the upper snowpack.  Slopes with a dusty, brown surface will warm faster and may produce larger wet loose avalanches.  Ideal conditions for riding have just enough softening for good turns, but the snowpack should remain supportive below.  If you find punchy and mushy snowpack head to a cooler aspect or lower angled terrain.

As meltwater infiltrates the snowpack, concerns for Wet Slab avalanches slightly increase.  An observation from near Snodgrass suggested that east and west aspects at low elevations have meltwater draining into a winter-like snowpack.  Rocky, bushy, and/or dusty surfaced terrain often moves meltwater faster than open, white snow slopes.  Wet Slabs are difficult to predict and manage.  A good rule of thumb is to start your day early and move off east and west aspects with wet snow surfaces earlier than usual.  This isolated and unlikely threat will linger until cooler weather arrives this weekend and meltwater production ceases.

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