Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind slabs both new and old can be found on a variety of aspects. Identify and steer around steep features with wind drifted snow to reduce the risk of triggering an avalanche. Expect greater danger during periods of heavy snowfall, intense wind transport, or strong sun.

Problemi valanghivi

  • Wind Slabs

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

    You will find wind slabs on a variety of aspects Tuesday. Day-old slabs from northeast winds are scattered about at treeline with more and deeper slabs in alpine areas. These are becoming stubborn to trigger, but be wary of steep, unsupported terrain features where you suspect wind-drifted snow. Another round of snowfall overnight Monday into the morning and moderate winds could build fresh slabs on slopes that were previously scoured down to the crust.

    While wind drifted snow was previously easy to identify, it’s going to be more difficult on Tuesday with new snowfall and periods of reduced visibility. Note areas where there is crust close to the surface (wind-scoured) versus where you are moving through deeper snow (wind-loaded). You are definitely traveling in wind slab when your skis or other floatation is getting stuck in a layer of softer snow below a more dense layer. Hand pits and test slopes can help you gauge the bond of wind slabs, but don’t ignore obvious signs of instability like whumps, shooting cracks, or recent avalanches. When in doubt simply avoid steep, wind-loaded terrain.

    (4/11/2022)

    A test slope produced a shooting crack on a south aspect at 5100'. This quick profile shows where the wind slab released over weaker snow below. The melt-freeze crust is the product of strong sun and warm temperatures on April 6-7th.

     

Avalanche Discussion

With the transition to spring, wet loose avalanches are possible anytime cold snow warms and becomes wet on sun-exposed or low elevation slopes. Move off and away from slopes where you see wet loose avalanches or other signs of instability during sun breaks or with rising temperatures. 

Strong, easterly winds were reported across the North and Central Cascades Monday. Despite plenty of wind redistribution near and above treeline, little avalanche activity was reported. A single large slab avalanche was spotted high on Shuksan which was probably the result of rapid wind loading. Test slopes and other tests produced mixed results with some being quite reactive while others would not even produce cracking.

At treeline there is 30cm of wind-loaded snow over the melt-freeze crust on leeward slopes. Many windward slopes are scoured down to the crust. At lower and mid-elevations, the storm snow from early April has mostly transitioned to a mix of melt-freeze crusts, melt forms, and moist rounded grains,

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