Avalanche forecast

West Slopes South

Northwest Avalanche Center
View on map

Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
Open full map
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Even though this isn’t a very big storm, recent avalanches, continued wind loading, and a known weak layer in the upper snowpack all employ you to take a conservative approach to your day. As you travel higher into the terrain or onto more shaded aspects you could encounter dangerous conditions that might be tricky to manage.

Avalanche problems

  • Persistent Slabs

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

    Information continued to roll in this week of human-triggered avalanches, audible whumpfs, and sudden snowpack test results. These observations have come from most parts of the West South zone. Even though the snow in front of you might not seem very dangerous, the growing list of avalanches suggests otherwise. Some of these slides were triggered remotely from nearby ridgelines and adjacent slopes. This is not a problem to try and outsmart. While snow profiles and snowpack tests can confirm the presence of a persistent weak layer, they cannot prove its absence. Give steep terrain on W-N-E aspects a wide berth. Persistent slabs can act in surprising ways like triggering from below, and even after several others have crossed the slope. 

    To add to the uncertainty, we’re in the middle of a storm. Even though it hasn’t brought a lot of snow, we don’t know how this weak layer will react to the new load. That’s even more true in wind-loaded terrain. This is only one more reason to dial it back and play it safe until the storm ends.

    (3/18/2022)

    A skier triggered avalanche on Mazama Ridge near Paradise, Mt Rainier NP. 16" deep. W aspect, 5600ft. This avalanche faild on the 3/8 facets over the Early March Crust. HS-ASu-D2-R3-O

    Public Field Report: Mount Rainier National Park, Mazama Ridge

    Photo: Public Observation

  • Wind Slabs

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

    Strong and gusty winds that shifted directions during this storm may have created wind slabs in some unusual locations and in a more sporadic pattern. You could find these potential avalanches on any aspect, well below ridgelines, and even further down in chutes or gullies. As more snow falls these slabs will only grow deeper. Be on the lookout for textured surfaces and firm drifts to help anticipate which slopes and features may hold wind-loaded snow. Steer around firm pillow-like drifts, especially in higher consequence terrain. As you ascend in elevations these avalanches may only get larger and harder to avoid. In the right terrain, one of these slides could serve as a trigger for a much bigger and scarier persistent slab avalanche.

    (3/16/2022)

    Wind slab avalanches from eariler this week. [E-NE 6700'; SS-ACc-D2-R2-I]

    Photo: Dallas Glass

Avalanche Discussion

This hasn’t been a big storm for the West South zone. Weather stations as of Saturday afternoon showed 4-6” of snow for most sites. Cooling temperatures and continued snow showers will slowly add to these storm totals through Sunday. Periods of sunshine may have formed a thin crust on southerly aspects within the storm snow. We’ve definitely reached that time of year when the sun frequently makes an appearance, even during a storm, and quickly affects the snow surface. Anytime the sun comes out during or right after a storm, anticipate loose wet avalanches. This could be the case Sunday too. 

On Friday we received a report of a human-triggered persistent slab avalanche in the Mt Rainier area. This adds to the list of avalanches from Wednesday at nearby White Pass and Crystal Mt. We also receive word of whumpfs and collapses in the White Pass backcountry. These all speak to this ongoing problem. The layer of concern is weak surgery facets (1-2mm) sitting just above the very stout and prominent Early March Crust. Prior to this storm, this layer was often observed down about 2-2.5 ft on W-N-E aspects. However, it was also seen on more southerly slopes near Mt Rainier. 

At lower elevations, there’s just not enough new snow to pose much of a risk. Instead, you may find breakable crust, firm rough surfaces, open creeks, and frozen avalanche debris all buried under just a few inches of new snow.  

Regions covered