Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

The degree of active or recent wind transport in your terrain will be the difference between slabs you can steer around and more widespread hazard. Evidence includes scoured ridgelines, pointy cornices above smooth, bulging pillows, and punchy snow layering. Steer away from steep, wind-loaded slopes.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Wind slabs will be increasing in size, distribution, and sensitivity to human trigger, both relative to Friday, and throughout the day. Low-density snow doesn't require a lot of wind to transport, so you'll need to be keenly aware of how the winds have impacted your terrain. Signs of prior wind loading include firmer layers within the soft snow, swales, large differences in depths of recent snow above the 12/18 crust, etc. Active wind loading is your most obvious clue that the problem is in your terrain and the deposition zone points to the problem, along with fresh, sharp cornices. Avoid steep lee slopes 35 degrees and steeper once you enter wind-affected terrain, and expect the problem to be widespread at upper elevations where you may not encounter a 12/18 crust. Don't underestimate the added risk of the early season hazards as sharp obstacles amplify your risk. 

    With 12" of snow forecast for the next 24 hours, we'd normally call this a storm slab problem and if you'd like to think of it that way, that is also appropriate. We are calling it a wind slab problem due to the expected significant overlap between slopes with enough snow to ride and wind-loading as windward slopes remain largely wind-stripped. You may also be able to get snow running as a dry loose avalanche on the steepest slopes.

    Example: Blowing snow and firm pillow-like drifts are great clues to anticipate wind load slopes. 

    Photo: ONP Rangers

Avalanche Discussion

Hurricane Ridge has around 17" of snow on the ground with the upper 6-8" of dry snow sitting above variable melt-freeze crust buried 12/18. This crust is thin and breakable in some locations, but supportable and upwards of 1" thick in other locations. It will be worth evaluating the bond to this crust as a similar crust contributed to touchy wind slabs and a remote trigger in the Mt Baker area on Friday. By Saturday you can expect that more than 50% of the snowpack has accumulated in the last 2 days. Below the fresh snow, you'll find the 12/18 crust. Because the snowpack was largely depleted at Hurricane Ridge, you may only encounter the mid-December crust where old snow survived at upper elevations and in wetter parts of the Olympics.

Snowpack information at middle and upper elevations remains limited throughout the Olympics. Move into it with an assessment mindset, keeping in mind the added risks of the early season snowpack. At lower elevations, there may be barely enough snow to recreate.

The weather over the past few weeks has been extraordinary, with torrential rains, extreme winds, flooding, and landslides. Many communities are dealing with damage to homes, infrastructure, and businesses, stretching resources thin. These events have limited access to the mountains for all of us. State and local resources are working diligently to reduce the worst of these impacts. We can help by being respectful of local communities, obeying road closures, and heeding ski area uphill travel policies.

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