Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Another round of stormy weather will result in dangerous avalanche conditions around the West South on Friday. The weather could play out differently depending on where you are in the zone, so be prepared to make your own observations to determine if conditions reflect your expectations. When in doubt, you should default to slopes under 35 degrees until this storm wraps up.

Avalanche problems

  • Storm Slabs

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

    More snow and wind, plus fluctuating freezing levels should be enough to create dangerous slab avalanches on Friday. You can use quick hand pits as you travel to look at the storm snow’s bond to the previous surface, heavy over weak snow, or to highlight layers of concern. Using small inconsequential test slopes can then give you information about how the storm snow is reacting to your weight. All of the snow above the easily identifiable Christmas Crust will be in play for possible avalanches, so take the time to check it out before committing to terrain. Slabs should be thicker as you ascend in elevation or in wind-loaded areas. If you see signs of cracking, blocks of snow failing easily, or recent avalanches, then you should avoid slopes over 35 degrees til this storm plays out.

    While we never exclude wind-loaded areas when talking about stormy conditions in the PNW. In some areas of the zone, less snow is expected on Friday, but the winds may be stronger. While the advice above still holds, you may want to also look for obvious signs of wind effect to help you determine wind-loaded slopes to avoid. Actively blowing snow, fresh drifts and cornices, or smooth pillow-like piles of snow that look “fat” are all signs that point toward wind-loading.

    (11/26/2022)

    Quick hand pits while you travel can give you an indication of how new snow has bonded to old snow surfaces or if it has come in upside down.

    Photo: Andy Harrington

Avalanche Discussion

Friday’s stormy weather should be the endcap to a weeklong stormy period that brought significant rain, freezing rain, sleet, snow, and wind to the West South zone. Needless to say, the snowpack has been through a lot in the past week and if you’re just returning to the mountains, you may find they look a bit different from when you last visited. The most recent changes have been from the wind. Wind Slabs were observed by NWAC forecasters on 12/28 in the backcountry near Crystal Mountain, and White Pass Pro Patrol reported significant wind transport during the same time period. 

Prior to the winds, an easily identifiable crust was formed by the rain over the Christmas weekend. The depth of this crust varies around the zone but could be about a foot deep at mid to upper elevations. At lower elevations or in wind-scoured areas, the Christmas Crust is much closer to the surface. Its thickness and depth vary by elevation and location but it should be the baseline of any snowpack tests you perform for the foreseeable future.

Along with the crust being formed, the rain also resulted in a myriad of wet avalanche problems around the West South. Rangers at Mount Rainier reported multiple Wet Loose and Wet Slab avalanches early on in the cycle. A few days later, Crystal Mountain Pro Patrol triggered multiple very large avalanches during their mitigation work. Many of these slides are thought to have failed on a weak layer from late November (11/22). The most recent occurrence of one of these very large avalanches was on 12/28. Although the lower snowpack still contains plenty of water, we believe the likelihood of one of these failing has decreased enough to no longer list them as an official problem. That doesn’t mean they’re impossible, a large trigger such as a cornice collapse or separate avalanche could theoretically tip the scales beyond the breaking point.

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