Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Generally safe avalanche conditions exist this morning. Then as snow surfaces warm through the day keep an eye out for specific terrain features that develop a small wet loose avalanche problem.  If you find yourself skinking to your ankles, or deeper into wet snow then you will likely be in an area capable of producing wet avalanches if the slope angle is steep enough. Persistent slab avalanches remain a very low probably but high consequence problem. The most suspect areas for triggering this avalanche problem would be where the snowpack height is variable and below average in depth. 

Avalanche problems

  • Loose Wet

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

    Sunshine and warming temperatures will increase the threat of shallow wet avalanches involving surface snow.  Watch for rollerballs, pinwheels, or natural sluffs to indicate developing instabilities, occurring first on east, then south, then west aspects.  Natural and triggered sluffs are most likely to initiate from very steep or rocky slopes or places with a dirty snow surface.  Be careful in or above consequential terrain once you find your feet sinking into a few inches of wet snow.  You can avoid triggering wet loose avalanches by riding on slope angles less than 35 degrees or moving to colder aspects.  

  • 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.  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

.05" of powder accumulated last night, with a mostly cloudy sky and cloud cover decreasing into this morning. Low temperatures are a few degrees warmer this morning than yesterday morning. Those overnight clouds will have decreased the snowpack's ability to lose heat, and frozen surface cruts may be a little bit thinner compared to yesterday's conditions. If you are traveling on steep southerly facing slopes this afternoon, keep an eye on how much wet snow is available for entrainment into a wet loose avalanche. Slopes with a dusty and brown surface or rocky terrain will warm faster and may produce larger wet loose avalanches due to increased melt.  Ideal conditions for riding have just enough softening for good turns, but the snowpack should remain supportive below.  If you find a punchy and mushy snowpack head to a cooler aspect or lower-angled terrain.  Conditions on the south half of the compass fit typical spring-time travel techniques.  By the afternoon, you may want to head for cooler northerly slopes to avoid encountering wet loose avalanche conditions.

As meltwater infiltrates the snowpack, concerns for Wet Slab avalanches slightly increase.  An observation from near Snodgrass on Tuesday and Schuylkill Peak area on Wednesday suggests that easterly and westerly aspects below about 11,500 feet 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. This isolated and unlikely threat will linger until cooler weather arrives this weekend and meltwater production ceases.

The Persistent Slab problem has become harder to trigger over the past week due to mild temperatures and a lack of recent loading yet the problem continues to linger.  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.  A natural avalanche in Terminator Chutes on Saturday and a triggered avalanche resulting in a very close call near Snowmass on Monday highlight the issue.  An observer near Little Italian Pass (just a few miles northeast of Star Mountain and outside the CBAC forecast area) reported a rumbling collapse and shooting cracks on an alpine slope facing northwest.  Avalanches from early in the week and the rumbling collapse occurred in terrain with a seasonally shallow snowpack and/or 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.  The Persistent Slab problem is more concerning in the Southeast Mountains where the snowpack is shallower overall.

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