Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Continued snow and wind will maintain dangerous avalanche conditions. Avoid steep open slopes greater than 35 degrees, especially those with evidence of wind loading. A complex snowpack still lingers and requires a very cautious mindset.

Avalanche problems

  • Storm Slabs

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

    The storm Friday/Saturday overproduced and the trend may continue Sunday. Expect to encounter 8-12in+ of recent snow atop variable old snow surfaces. Thicker and more reactive slabs exist in wind-loaded upper elevation terrain. With cold temperatures, additional snowfall will continue to accumulate at low elevations Sunday. The recent snow needs time to settle and stabilize. Fresh slabs will be reactive to human traffic in all elevation bands on slopes 35 degrees and steeper. In areas sheltered from the wind, loose dry sluffs may run far and fast in steep terrain and could even trigger slab avalanches as they run downslope. Carefully assess how new snow bonds to itself and old snow surfaces. Watch for shooting cracks, collapses, and recent avalanches. Avoid large open slopes and convex rollovers and seek out lower angled and supported terrain.

    (2/13/2021) Shooting cracks in the storm snow on an east aspect at 3200ft above the Mountain Loop Highway. Photo: Steve Kuznetsov

  • Deep Persistent Slabs

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

    Very large avalanches failing on a persistent weak layer buried 4-6ft deep may still be possible near and above treeline. The layer continues to become more difficult to trigger with time. Large triggers like cornice fall or motorized users are more likely to affect such a deeply buried weak layer, but just the weight of a person may still be enough. Above 4500ft, treat broad open slopes 35 degrees and steeper guilty until proven otherwise. 

    These conditions come with uncertainty and present a low likelihood/high consequence scenario. Observations targeting this layer continue to show gradually improving stability, with signs of the weak layer healing (rounding) and more favorable snowpack test results (resistant and non-planar fractures and no propagation). Regardless, variability exists and additional time is needed to more accurately assess the sensitivity and distribution of the weak layer. Continue to build in a wide margin for error and approach terrain with a very cautious mindset. Utilize good travel practices like riding one at a time and keeping eyes on your partners. If you must travel near or below steep upper elevation slopes, your best options are areas where avalanches on this layer already occurred.

    (2/11/2021) Natural slab avalanches that ran in early February along the east side of the 3 Fingers Mountain area in the West Central Zone.

Avalanche Discussion

Cold, low-density snowfall and steady winds will continue through the holiday weekend bringing dangerous avalanche conditions. Avalanches within new and wind drifted snow are likely on steep open slopes and could grow large. In some areas, the new snow may rest atop weak old snow surfaces with the potential for surprising and widely propagating avalanches. A lingering deep slab instability still weighs heavily on our minds and demands very cautious terrain and travel choices. In addition to a complex snowpack, very cold temperatures Sunday will increase the consequences of any incident, avalanche-related or otherwise. 

Unfortunately, a snow biker triggered an avalanche on the deep persistent layer in the East Central zone on February 8 and was buried and killed. For more details and information, see the Accident Reports page and the post-incident investigation video below. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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