Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Give the snowpack time to adjust to the large amount of water we have just received by staying off slopes greater than 35 degrees on Tuesday. Avalanches may be large enough to injure, bury, or kill you, demanding you to use conservative decision-making. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    We have had almost continuous, and often heavy, precipitation since 12/29 around the West South, which has created some variability within the zone. What seems to hold true throughout, is that several potential weak layers may now exist in the upper snowpack. We are calling these Storm Slabs due to the larger water numbers that have been received on the volcanoes, but in areas closer to the crest that have received less water, you may be managing the hazard more like Wind Slabs. 

    Regardless of location, slab likelihood will increase as you ascend in elevation and on wind-loaded slopes on Tuesday. Slabs may involve new snow or break several feet deep into the storm and wind-loaded snow from the past week. Slabs that start small could also entrain significant amounts of snow resulting in large avalanches. Check for strong snow over weak snow, storm density changes, and bonding to the old snow surface as points of failure for any potential slab. Using hand pits and test slopes may not give you enough information to clearly identify deeper layers of concern. When dealing with wind-loaded terrain, look for textured surfaces or firm hollow-sounding snow as areas to steer clear of. If you are in doubt, default to terrain less than 35 degrees and allow the snowpack time to gain strength.

    (1/3/2021) Up track tests like this can highlight weak layers in the new snow for both wind and storm slabs. However, the only work as deep as your skis, snowshoes, or machine sinks into the snow. other weak layers could hide deeper.

Avalanche Discussion

The ongoing storm cycle continues to favor the volcanoes with the highest snow totals and likely greatest avalanche hazard in the zone. However, all areas in the West South zone have received notable precipitation since 12/29 (Paradise 9.02”, Crystal 4.39”, White Pass 4.21” as of Monday evening). In general, multiple feet of cold, dry snow sit atop a thin crust (1/1) that was formed by a brief warmup on New Year's Day. This crust may be difficult to find in some locations but may present itself to you when performing stability tests since we believe there to be some weak snow sitting just above it. Below the 1/1, you will again find multiple feet of mostly cold and dry snow sitting atop the 12/21 crust. 

We expect the bulk of avalanche activity on Tuesday to occur in the snow above the 1/1, which contains multiple potential weak layers. However, the threat remains for deeper layers below the 1/1 to fail, creating very large and deadly avalanches. We wouldn’t be surprised to hear of some isolated D3 avalanches occurring over the next few days. Natural avalanche activity should be trending downward on Tuesday, but still possible, while human triggered avalanches continue to be a major concern. Additionally, observations from the highest elevations have been extremely limited due to the ferocity of the storm cycle, giving us a fair bit of uncertainty. If the middle and lower elevations are any indication, we have had plenty of avalanche activity up there and suspect that to continue Tuesday where the conditions are ripe for possibly creating the largest and most destructive avalanches.

With cooling temperatures and some new snow, Loose Dry avalanches should also be on your radar on Tuesday. The slides can entrain snow and even trigger slabs as they run downhill. Don’t get swept off your feet by one of these slides in consequential terrain. Lasty, due to the significant storm totals in the past week, deep snow alone can be dangerous. Make sure to travel with a partner and to be aware of the danger. You can learn more at www.deepsnowsafety.org.

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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