Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Wind slabs will be large, stiff, and surprising, potentially breaking well above you and running efficiently on a crust. Your risk increases rapidly with elevation, so ascend with attention for firm, punchy snow.  Give upper-elevation slopes steeper than 35 degrees another day to heal and steer around steep, wind-loaded terrain features near treeline. 

Avalanche problems

  • Wind Slabs

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

    Recent snow combined with strong winds at upper elevations Friday night to produce firm hard slabs that you could trigger. Crystal Mountain picked up 8-9" of snow and Paradise picked up about 10." Strong SE winds at Crystal blew the new snow into hard slabs that produced two notable large avalanches with 1.5-2.5 ft crowns that released easily in mitigation on Saturday morning. Hard slabs tend to be slow to heal and we think they will maintain reactivity at upper elevations throughout the region on Sunday. They sit on a variety of snow surfaces including an icy crust (12/21) and weak soft snow above that crust.  Increased alertness as you ascend in the terrain and consider any slope guilty of wind-loading until proven innocent. Navigate around shallow wind slabs as you transition into wind-affected terrain, but expect widespread wind-affected snow above 6000 ft where you are most likely to find firm or punchy layers, whumphs, or cracking as indicators of instability. At these upper elevations, choose slopes less than 35 degrees to avoid triggering a large avalanche.

    Below treeline and in other areas with less wind-affected snow, Dry Loose avalanches may be triggered on slopes approaching 40 degrees.

    (12/26/2020) Hard slab 1.5-2.5 ft thick, running on 12/21 crust.

Avalanche Discussion

We're expecting increasing chances for sunshine as the day wears on.  When the sun does appear, pay attention for rollerball activity and adjust your aspect before Wet Loose avalanches release from steep, southerly slopes.

Expect the avalanche danger to gradually decrease with minimal new snow and wind transport Saturday night and Sunday.

Observations from the West-South prior to Friday night's storm showed variable snow surfaces prior to Friday night's wind-loading event, which means slabs will be slower to heal than you expect. An icy crust (12/21)  formed during last weekend’s rain events and serves as the most prominent marker in the upper snowpack. In some locations, this crust is exposed due to recent winds creating very firm and slippery conditions. In other spots, 4-12” (10-30cm) of recent snow sits above the crust. You may encounter ice, breakable crust, wind deposits, and soft snow over a very short distance. Any avalanches should be limited to the snow above this recent crust. 

Even with all the snow this winter, creeks remain open at most elevations. Choose crossings carefully and give yourself extra time to navigate around these and other early season hazards. 

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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