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

Tricky snowpack conditions combined with additional snow and wind warrant extra caution during these particularly dangerous conditions. Stay off of all open slopes greater than 30 degrees.

Avalanche problems

  • Wind Slabs

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

    Windy conditions continue to impact the West South zone especially in locations near the Cascade crest, like Crystal Mt, Chinook Pass, and White Pass. On Monday southeasterly winds formed slabs on some unusual aspects, often with loading patterns opposite of normal. As winds shift to the SW on Tuesday and snow keeps falling, you could encounter wind loaded slopes on any aspect. Keep a keen eye out for subtle signs of wind loading. Changes in how the snow feels under you or differences in the depth of soft snow could indicate the wind transported snow. Newer shallower drifts could be easier to spot, but older larger wind slabs may exist in much less obvious locations. If you suspect wind loading on a slope, steer around and seek our lower angled or less wind-affected areas.

    In some spots, these wind slabs may overlay weak persistent grains allowing them to trigger easily or act in surprising ways. On Monday, an intentionally triggered wind slab stepped down into deeper older snow layers. This combination of avalanche problems could result in tricky and potentially dangerous conditions. Use extra caution and don’t default to your normal wind slab travel patterns. 

    (2/1/2021) This small wind slab avalanche stepped down to the 1/23 facets above the thick prominent crust. Gunsight Bowl: N aspect, 6300', 18" crown. HS-ASc-D1.5-R2-O

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Weak persistent grains have been identified in nearly every area of this zone including the Crystal and White Pass backcountries and locations around Paradise. Each day we receive reports of surprising avalanches. This continues to reinforce the persistent nature of this problem. In short, it has not gone away. The primary culprit seems to be a layer of weak facets just above the prominent 1/13 crust. In some locations these sit 12-24” or more below the snow surface. While snow profiles and snowpack tests can highlight these layers for you, they can not indicate if a slope is safe. Your best defense against a persistent slab problem is to dial it back and stay off of all slopes greater than 30 degrees.

    (2/1/2021) This snow profile from Miriam creek near White Pass shows the facet layer of concern.

Avalanche Discussion

Snow continues to pile up at mid and upper elevations around the West South zone. In many spots, the prominent 1/13 crust is 2-3feet deep. Hiding in this upper snowpack are several persistent layers. The most notable seems to be a layer of facets sometimes accompanied by surface hoar or a thin crust. This layer sits just an inch or two above the 1/13 layer. While this structure seems to exist in all areas and on multiple aspects, the majority of avalanches, shooting cracks, and collapses seem to have occurred on NE-S-W aspects in the near and above treeline bands. Numerous confirmed or suspected avalanches on this persistent weak layer occurred at Crystal, White Pass, and Mt St Helens over the past few days. So, far we have not received observations of avalanches on this layer near Paradise or the Tatoosh. 

In some areas, the 1/13 crust shows signs of breaking down with faceting on the underside. While this may become an issue going forward, it should not overshadow the weaker layers above the strong crust that you are more likely to trigger. 

At lower elevations (<5000-5500’), warmer temperatures and rain on Monday moistened the upper snowpack. As temperatures cool and the surface freezes, this should help limit the avalanche danger at these lower elevations. As this occurs expect breakable crusts and “punch” travel conditions.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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