Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

With a potentially tricky snowpack, significant changes in the weather, and plenty of uncertainty around the West South zone, consider dialing back your route options Friday. Wind affected slopes and terrain in the sun may produce avalanches that run quickly on an underlying crust. 

Avalanche problems

  • Wind Slabs

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

    Strong E-SE winds, particularly near the Cascade crest, formed slabs in some unusual locations and aspects earlier this week. In the Crystal backcountry, several small avalanches were observed Thursday by an NWAC forecaster. These slides were around 8” thick on SW facing slopes. Look for subtle clues such as small drifts and changes in the feel of the snow underneath you to locate wind affected slopes. You may find wind slabs well below ridgelines and along the sides of cross-loaded gullies and features. Some of these slabs may be more than a foot thick and could produce avalanches large enough to bury you. If you suspect wind loading on a slope, go around and seek out less wind-affected or lower angled terrain. 

    We continue to find evidence of buried persistent grains in the Crystal area. We are uncertain if a similar snowpack structure exists in other parts of the zone. If these wind slabs fail on facets, surface hoar, or crust/facet layers they may produce surprising avalanches that trigger easily, propagate widely, and run quickly.

    (1/28/2021) This small slab avalanche occurred well below ridgeline on East Peak Thursday. Other similar slides were observed later in the day.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    We expect significant sunshine for the first time in several days across much of the region. This will likely result in a natural loose avalanche cycle on steep rocky slopes receiving direct sunshine. While these slides should remain small, they may run farther than you expect on a firm underlying crust. If you notice the snow shedding from trees or see new rollerballs, anticipate loose wet avalanches. Steer around similar sunny slopes. Even small loose slides can harm you if they push you over a cliff or bury you in a gully.

    (2/24/2020) Rollerballs like these are a great indication that the snow surface is becoming wet and unstable. They can be the precursor to loose wet avalanches. When you see new rollerballs, steer away from similar slopes.

Avalanche Discussion

In sheltered areas, you may find between 8 and 18” of recent snow over the prominent 1/13 crust depending on your location in the West South zone. This thin upper snowpack resulted from a series of small storms over the past week. If you look at the snow above the 1/13 layer you may see several subtle interfaces including weak facets, buried surface hoar, and thin crusts. It’s these persistent grains that really have our attention. While several observations confirmed the presence of buried weak layers in some areas of the Crystal backcountry, we have a high degree of uncertainty in other parts of the zone. If you travel near Mt Rainer, White Pass, or Mt St Helens please let us know what you find. Persistent weak layers can be tricky and can require digging and a keen eye to locate. With such low-density snow overlaying the 1/13 the missing piece in the recipe may be a slab. As temperatures warm and the snow continues to settle, that may change. 

We expect any avalanche activity to occur about the prominent 1/13 crust. This layer shows some signs of weakening and faceting below. While not a current issue, this will be worth monitoring going forward. 

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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