Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Numerous recent avalanches and whumpfing collapses are red-flag signs of instability that should have your attention. Weak snow exists above a crust on shaded slopes at mid to upper elevations. You should avoid slopes over 30 degrees in these areas until the snowpack has more time to heal.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    It was a very active day avalanche-wise in the West South zone. More details can be found in the discussion but multiple avalanches broke on the 3/8 facets above the Early March Crust. This gives us enough confidence to officially label this as a Persistent Slab issue. Prior to the recent storm, we found these facets to be most pronounced on northerly aspects at mid to upper elevations. The exception is at Paradise where we found them on multiple aspects. Persistent slabs aren’t a problem you want to try to outthink or manage. These slabs can break in surprising ways by spanning far distances, connecting terrain features, or breaking far above you. They can also be triggered remotely from ridgelines or flat terrain below a slope. You’re going to have to dig down to the Early March Crust in whatever area you are recreating and take a look to see if this weak snow exists just above it. You could find that the weak layer is capped by a thin (1cm) crust, making this a bit of a “sandwich” setup. If you suspect this weak snow is present or are in terrain where it could be, you should avoid slopes over 30 degrees.

    (3/16/2022)

    A remotely triggered avalanche in the White Pass backcountry. This was triggered from the ridgeline by a skier. [NE 6200' SS-ASr-D2-R2-O]

    Photo: Dallas Glass

  • Wind Slabs

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

    While the persistent slabs are certainly the scariest problem to deal with out there right now, you should also be leery of triggering an avalanche in wind-drifted terrain on Thursday. The winds were strong with this storm, creating fresh cornices and Wind Slabs in many locations. The storm also finished cold, leaving behind low density snow that is available for transport in the days to come. You can use visual clues like those freshly built cornices, textured surfaces, or drifts behind objects to help you identify wind-loaded terrain to avoid. These slabs often like to form near ridgelines, convex slopes, or rocky features such as confined gullies or the base of cliffs. They will be easier to trigger if the slope is over 35 degrees.

    (3/16/2022) Fresh cornices and smooth pillow-like piles of snow indicate wind-loading. Photo: Andy Harrington

Avalanche Discussion

What a day for the West South zone. The 3/8 facets that we had been tracking prior to this storm decided to rear their ugly heads along the crest and parties near both Crystal and White Pass were remotely triggering avalanches on them. Additionally, some natural activity was observed on this layer and in wind-loaded terrain near White Pass. NWAC forecasters in the Crystal Mountain Backcountry confirmed that the facets survived the storm and were very reactive in both small and large column snowpack tests. Later we received word of two human-triggered avalanches suspected to be on this layer just a stone’s throw away from where we were digging. At least one of these slides was remotely triggered. Down at White Pass, off-duty NWAC forecasters remotely triggered multiple avalanches on the 3/8 facets from ridgelines and experienced several loud whumpfing collapses. Other parties in the area reported triggering their own slides remotely, at least one of which was in lower elevation terrain. All of these slides happened on northerly aspects, most of which were NE. We do not have any information from Paradise, Mount St. Helens, Government Meadows, or anywhere in between. Regardless of your location, take these slides into account and let them shape your travel plans.  Please help us track this layer by letting us know what you find out there by submitting a public observation.

Besides the barrage of avalanches, recently built and sensitive cornices and wind-drifted snow were reported at both Crystal and White Pass. At least in the Crystal area, the snow on sunny slopes got heavy and wet as temperatures and sunshine destabilized the surface. Crystal Mountain Pro Patrol reported triggering small wet avalanches easily with ski cuts during the morning. This will be a persistent issue for us for much of the remainder of the season and we could probably forecast Wet Loose almost every day. Thursday will be no different. As light precipitation rolls in, fluctuating freezing levels could produce rain or heavy wet snow at mid to lower elevations. Keep wet avalanches on your radar anywhere you encounter wet and sticky snow.

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