Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wednesday will bring the last round of snowfall and moderate wind before clearer weather later in the week. Identify and avoid steep slopes loaded up with wind-drifted snow. Human-triggered avalanches over the weekend show the need for extra caution in wind-exposed terrain. Fresh snowfall and avalanche danger will be the greatest on the volcanoes.

Problemi valanghivi

  • Wind Slabs

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

    Danger from wind slab avalanches will consist of older, stiff, and stubborn slabs that formed in previous days, and also shallower slabs built by fresh snowfall and wind. Wind slabs often heal quickly and become unreactive. But the last few rounds of wind drifting added enough load to weaker layers below that we are seeing avalanches unusual in size and character.

    Blowing snow and fresh drifts point the way toward the slopes that are actively loading. You’ll also need to hunt down deeper, older wind-loaded areas. Scoured slopes and larger wind features can help you find these spots. You can also track the snow depth over the thick Early February Crust to figure out which areas are more or less wind-loaded.

    Slab avalanches in wind-sheltered terrain are possible in parts of the zone that see the most snowfall on Wednesday. Near the Cascade crest, you’ll likely experience lower danger. 

    (2/19/2024)

    Deep crown of a human-triggered wind slab avalanche near Crystal. North aspect at 6300'. It likely failed on a layer of weak facets above a crust. 

Avalanche Discussion

Snow levels should be low enough that most areas will see snow instead of rain. If the rain-snow line is higher than forecast, look for an increase in wet avalanche activity like rollerballs, pinwheels, and small loose snow avalanches. 

The upper snowpack consists of layers of settled snow, crusts, and facets over the Early February Crust (EFC), often 12-30 inches (30-75cm) below the surface. The exact depths and layering depend on aspect, elevation, and exposure to sun and recent strong winds. A layer of facets has been consistently identified above the EFC at Crystal, Paradise, and White Pass.

Strong easterly winds, periods of sun, and some warm temperatures created a hodgepodge of surface conditions over the last week. Breakable or semi-supportable crust is found on solar aspects while northerly slopes hold anything from soft wind-drifted snow to thick, settled powder. Ridgelines and start zones facing the wind are generally scoured down to a crust and quite slick.

 

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