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

Continue to avoid northerly facing slopes over 30 degrees at upper elevations. This is the most likely location for unpredictable and dangerous avalanches on Friday. Elsewhere, keep your eye out for wind-drifted piles of snow to steer around as you ascend in elevation.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Continue to avoid northerly facing slopes at mid and upper elevations over 30 degrees until the snowpack has had more time to heal. Persistent slab avalanches are not a problem that you can outthink or tip-toe around. They are erratic and basically unpredictable. On Wednesday, a party who remotely triggered a slab in the West South said they had first dropped a cornice onto the slope and it did not slide. They took two steps along the ridge, heard a whumpf, and then the entire slope failed. This highlights the unpredictable nature of these kinds of slides. You can dig down to the Early March Crust and look for weak snow just above it to confirm the existence of this layer, but I wouldn’t bet my life on a single hole in the ground as a tool to rule it out. Don’t ignore red flag signs of instability such as whumpfing collapses, shooting cracks, or recent avalanches. These are nature’s way of giving you warning signs, so be smart enough to listen to them.

    You may notice that we do not have an avalanche problem forecasted for the below treeline band, but are holding a moderate hazard rating. Due to the unpredictable nature of these avalanches, it is hard to call any elevation band generally safe at this time even though we have typically found this persistent issue at middle to upper elevations.

    (3/17/2022)

    Crown of the 3/16 remote triggered avalanche on the shoulder of Three Way Peak. You can see the Early March crust and weak sugary snow (facets) that this avalanche failed on.

    Photo: Robin Pendery

  • Wind Slabs

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

    You also could be dealing with some pockets of Wind Slab as you travel. These slabs should be larger as you ascend in elevation or on the volcanoes where more snow fell during the storm. Look for textured snow surfaces or recently built cornices to help you identify aspects where these slabs could be lurking. If you notice smooth pillow-like piles of snow or feel that the snow is stiffer, you have likely found an area of concern. You’re more likely to trigger a slide on a convex rollover, unsupported slope, or near rocky terrain such as the base of cliffs or confined chutes and gullies. 

    (3/16/2022)

    These slabs were triggered after a cornice was dropped on the slopes below by skiers. They are most likely Wind Slabs. [E-NE 6700'; SS-ACc-D2-R2-I]

    Photo: Dallas Glass

Avalanche Discussion

On Thursday, NWAC observers in the Crystal Mountain area investigated Wednesday’s reported avalanches and confirmed that they failed on the 3/8 facets and ran on the Early March Crust [Observer observation]. Similar avalanches at White Pass on Wednesday are confirmed to have run on this same setup. The Early March Crust is generally 15-20” below the surface near the crest and was found to be 27” down at Paradise by NPS rangers on Thursday. Rangers had poor visibility but did not immediately spot any recent avalanches that could be tied back to this layer. We are still lacking information about the existence and reactivity of the 3/8 facets in many areas of the zone, but that doesn’t mean that you can just ignore the problem. The recent avalanches and other red flag signs of instability such as whumpfing collapses should be enough to make you realize that this problem isn’t your typical storm slab or post storm instability. Gathering the stories from these recently triggered avalanches, a few key points come to mind:

  • You can’t just dig one hole in the ground and call it safe.  However, if you find this poor setup, you can feel good about avoiding similar terrain.
  • Just because you see tracks on a slope, doesn’t mean it’s safe. It could be the 2nd, 3rd, or 4th person who triggers an avalanche. 
  • Even large tests like dropping cornices are no guarantee of a slope's stability.
  • The snow may look very enticing for recreation but you may need to show some restraint and think about the consequences if you’re wrong.

On Thursday night, a quick shot of precipitation should impact many areas of the zone. While these water numbers aren’t very impressive, take a look at how any new inputs are affecting the snow surface in your area. Snow that was once light and fluffy could be heavy and moist due to drizzle at lower elevations. A new bit of storm snow could be sitting on top of a firm sun crust and slide easily. Or perhaps the new snow adds an additional layer for you to investigate before committing to a slope. However it plays out, be sure to keep wet avalanches on your radar anywhere you encounter wet and sticky snow. The springtime weather has a way of moistening the surface snow even on days when it's not expected.

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