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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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The storm isn’t over for the southern part of the West South zone. Regardless of location, the snowpack will need time to adjust to the recent load and should be primed for human-triggered avalanches on slopes over 35 degrees. Areas that received significant snowfall or recorded high winds will be the more likely locations for these avalanches to occur.

Avalanche problems

  • Storm Slabs

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

    The recent storm likely formed Storm Slabs throughout the zone that you will need to investigate before heading into avalanche terrain. In the southern half of the zone, continued snow and wind on Sunday should help to thicken these slabs. You want to target the interface between the recent storm snow and the old snow surface as your primary point of failure. There could be interstorm layers to investigate as well, and slabs could be thicker and possibly more reactive as you ascend in elevation or in wind-prone areas. You can use uptrack tests as you travel to look for shooting cracks or failing blocks of snow to help indicate slab potential. Hand pits can help you identify your layers of concern, and test slopes can help indicate how the recent snow is reacting to your weight. If any of these tests indicate unstable snow or you find heavy snow over weak snow in your pits, avoid slopes over 35 degrees.

    (12/11/2021)

    During a stormy Saturday last weekend, this avalanche in the Crystal Mountain area caught a party of 6 tourers and unfortunately resulted in a fatality.

  • Wind Slabs

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

    We often don’t pair Wind Slab and Storm Slab together, but it is impossible to ignore the winds near the crest during this storm. Before the warmup on Saturday, dry cold snow existed throughout the zone and winds approached 100 mph in multiple locations. Wind Slabs may have formed on leeward slopes near ridgelines, at the base of cliffs, or the sides of gullies during this time and could be reactive on Sunday. These slabs may continue to thicken as the storm lingers in parts of our zone, or new slabs may develop as winds shift towards the East on Sunday. Your best bet is to look for wind-textured surfaces, fresh cornices, or blowing snow as visual clues of Wind Slabs. These slabs are often firmer than the surrounding snow and may feel hollow. If you notice any of these signs or suspect that a slope is wind-loaded, avoid it and stick to slopes less than 35 degrees.

    (12/10/2021)

    Visual clues can help you identify that Wind Slabs may be present.

    Photo: Dallas Glass

Avalanche Discussion

This storm has been highly variable around the West South zone and areas from White Pass southward may not be out of the woods quite yet. Paradise has once again received the most precipitation, but areas closer to the crest recorded the higher winds. Regardless of your location in the zone, this was a significant storm and the snowpack will need time to adjust to the recent load. Observations have been limited, but we suspect that the snowpack is now primed in many locations for human-triggered avalanches to occur on Sunday. Most avalanches should take place in the upper snowpack, possibly near the new crust that surely formed due to the warmup on Saturday. Take a look at the new/old snow interface, check for wind loading, and then investigate for interstorm layers or weak snow near the new crust for potential points of failure. When in doubt, head for lower angled terrain.

The lower elevations surely took a bit of a beating during this event due to rising freezing levels. This results in a lower avalanche hazard but increases the early season hazards we have been talking about recently. Open creeks, shallowly buried stumps, rocks, and other natural hazards will continue at these elevations as we continue to build our early season snowpack.

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