Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

That was one heck of a stormy week! While the danger may be slowly dropping, the treat for large and deadly avalanche hasn’t totally gone away. All steep open slopes are suspect, but slides may be more likely on convex rollovers, in complex terrain, and in wind loaded areas.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    It’s hard to say how fast or slowly all the new snow is healing. However, with feet and feet of storm snow on the ground, avalanches may easily become large and deadly. These probably won’t be a version of storm slab you want to mess around with. So, give them a wide berth by sticking to treed, smaller, and lower angled slopes. 

    One thing that’s tricky in the current situation is we can’t rely on many of our common storm slab observation tools. There’s just too much snow to use hand pits, up-track tests, and small slopes. Instead, we just need to patiently wait and give the snowpack the time and space to heal. 

    At higher elevations, strong winds may have built hard, thick slabs. If you find very firm hollow snow, head to lower angled or wind stripped terrain. These hard slabs are notoriously difficult to predict and can result in very large avalanches.

Avalanche Discussion

That was a wild, wet week! Since March 8th, storm after storm focused on the West South zone. While totals vary, most sites recorded 8-12 inches of precipitation, resulting in 60-90 inches of snow, and snow depths nearly doubled! Not too shabby! However, downed trees, power outages, and road closures limited access.  As the storm ended on Saturday, the sun came out and likely left a thin crust on southerly aspects. Sadly, the cold, snowy week is over. Our next system arrives on Sunday with increasing clouds and slowly rising temperatures. Unfortunately, this storm is much warmer. Precipitation should start by late afternoon, but rain reaches into the middle elevations Sunday night and Monday. Conditions could change quickly as the storm ramps up, especially if it sags a little further south. 

The upper snowpack seems to be settling and gaining strength. However, there are two layers to use as markers and to keep an eye on. The 3/12 interface is a layer of denser snow, often 3-4 feet (90-120cm) below the surface. This layer may have contributed to some of the avalanches reported on Friday. The 3/8 crust is at the base of all the new snow, typically 4-6 feet (120-180cm) down. While observations were quiet on Saturday, the USGS reported several very large avalanches on Mt Saint Helens and Mt Rainier. One slide on Rainier, originated near the Kautz Glacier/Mildred Falls and ran for 8 min!. 

It’s deep out there, and snow immersion is a risk. You can learn more about deep snow safety here. 

Remember, this past week has been a big change to the snowpack. After big multiday storms, we often have a higher level of uncertainty. Therefore, it may be prudent to give the snowpack a bit of time and space by keeping terrain small and simple.

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