Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

You may find firm pockets of wind-loaded snow in some strange places on Sunday. This could include unusual aspects, well below ridgelines, and exposed mid-slope features. Expect these potential avalanches to be more common and dangerous as you ascend in elevation.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    These wind slabs seem to be catching people by surprise. We’ve received reports of at least 8 unintentionally triggered avalanches around the region in the past two days (Fri/Sat). Fortunately, they didn’t result in any injuries or deaths, despite some high-consequence terrain. This highlights the unique nature of this beast and suggests we may want a bit more of a buffer than usual.

    A sustained strong and gusty easterly wind event built firm slabs in some odd places. You’re common “safe” routes might just hold the hazard. Look for scoured slopes, textured surfaces, and drifts to highlight local wind patterns and help anticipate potentially loaded slopes. Remember, these may occur well below ridgelines and along mid-slope gullies. 

    Wind slabs are often hard to assess (that’s why we use visual clues). Small slopes don’t always give us a complete picture. Some of these slabs may be hard and could break above you or fail on an underlying crust and propagate widely. Seek out more sheltered terrain to put space between you and this problem.

    (2/16/2024)

    Visual observations help you anticipate wind loaded slopes.

    Photo: Dallas Glass

Avalanche Discussion

A weak storm should bring a bit of snow to the West South zone Saturday night into Sunday. This storm favors the volcanoes, but accumulations anywhere should be modest. The new snow by itself won’t pose much of a hazard. If anything, it might only make the wind slabs harder to spot. 

On Friday, a wind slab avalanche was triggered on Panorama Face at Mt Rainier adjacent to a very common travel route. Crystal Mt Ski Patrol also reported widely propagating slides, some of which ran on firm crust layer. On Saturday, we received reports of long shooting cracks in wind-affected snow. These are all clear indications of an ongoing wind slab problem. 

One other factor that might make this current situation unique is the presence of various crusts and facets in the upper snowpack above the Early February Crust (EFC). In some places, these layers produce concerning test results; in others, they don’t. It seems likely that if an avalanche involves these deeper layers, it would likely still be in wind-loaded terrain. 

Field reports from Saturday are a bit sparse, but a new sun crust seems to have formed on steep southerly slopes, particularly in sheltered terrain. More northerly aspects continue to hold soft, dry snow. However, anywhere the wind reached, you may find scoured slopes, breakable crusts, large wind features, and firm drifts.

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