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

As the storm wraps up, you’ll be left with new snow problems to manage on Tuesday throughout the West South zone. The depth and reactivity of potential slabs may vary based on the amount of storm snow in your area. Be sure to check for layers of concern and be leery of slopes over 35 degrees where triggering a slide is more likely. 

Avalanche problems

  • Storm Slabs

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

    Snowfall should cease by Tuesday morning after nearly constant waves of precipitation have impacted the zone since Sunday evening. Expect to encounter unstable slabs on steep slopes over 35 degrees or in wind-loaded areas near ridgelines and rocky terrain. Larger and potentially more reactive slabs will exist as you ascend in elevation or in areas that received more significant storm accumulations such as the volcanoes. In areas closer to the crest, you may find that you’re managing more of a Wind Slab problem. Regardless of the slab character, using uptrack tests or small test slopes can help you determine how easily and deeply the new snow is failing. Digging quick hand pits to check the initial bond, determine if the snow came in “upside down” (heavy snow over weaker snow), and locate interstorm layers of concern can further help you identify slab potential. If you notice a poor bond or that snow is failing as blocks during your tests, avoid slopes over 35 degrees.

    (2/11/2023)

    Look for shooting cracks, blocks of snow failing on test slopes or uptrack tests, or recent avalanches as signs that the snowpack is unhappy and needs time to heal. 

    Photo: Andy Harrington

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    With cold dry snow in place and the sun expected to make an appearance as this storm wraps up, we can’t rule out solar-induced loose avalanches on Tuesday. As is typically the case, it remains to be seen if this one plays out as a battle between cold temperatures and sunny skies unfolds. If sunshine wins, you could see avalanches that start at a point and fan out as they move downhill. They’ll be most likely on steep slopes over 35 degrees that see direct sunshine and will be preceded by rollerballs or pinwheels. You may see them initiated by snow shedding from trees or rocks even if the snow surface isn’t yet wet and sticky - manifesting more like a Dry Loose. Regardless of the moisture content, their behavior and management remain the same. If you notice the signs, don’t get tripped up by one in consequential terrain and you can always head for shadier slopes to avoid them altogether.

    (2/11/2023)

    Example: small loose avalanches and a few rollerballs on a steep sunny slope. These ones originate near trees and rocks.

    Photo: Andy Harrington

Avalanche Discussion

Monday’s storm is forecasted to linger through the evening hours and is expected to continue to deliver snow to the West South zone before quieter weather takes over on Tuesday morning. The volcanoes (St. Helens, Rainier, and Adams) could pick up as much as a foot of snow and will outpace areas closer to the crest where somewhere in the range of an additional 4-6 inches are anticipated. 

Observations from Monday are limited, but Crystal Mountain Pro Patrol reported that a lack of rain resulted in new snow falling over a firm crust, resulting in a moderate bond. In other areas of the zone, high-elevation rain at the start of the storm likely created a wet surface and a more favorable bond. We have not received word of any new avalanches.

We envision most avalanches occurring within or at the base of the new storm snow on Tuesday. Although not expected, we wouldn’t be shocked to hear of a few avalanches breaking into deeper layers. That said, anything deeper than the 2/3 interface would certainly be a surprise.

Regions covered