Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Avalanche danger is low except in terrain holding recently drifted snow. Identify and avoid steep slopes with pillow-like drifts, dense slabs, or where there are signs of instability like long, shooting cracks and whumphing. A couple inches of snow may fall by the end of the day Saturday, which could result in more new shallow drifts. 

Problemi valanghivi

  • Wind Slabs

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

    Newly formed wind slabs have been the main problem in the last few days. We've had some recent lulls, but anything from few-day-old wind slabs to shallow new slabs in the couple inches of snow we expect by the end of the day could result in avalanches. A shift in the wind could mean new slabs building in different locations from what you previously saw. 

    Thursday and earlier in the week, backcountry travelers reported being surprised by triggering, and some getting caught, in sneaky wind slabs in different areas of the zone (observation, observation, observation). Wind slabs typically bond quickly, but they still might be easy to trigger if they formed over weak, faceted snow, over another variety of weak surface, or a crust. Reactivity could be different from feature to feature so don't assume that finding unreactive slabs on one slope means others will behave the same way. 

    Most wind slabs should be small, but some might be larger, or possibly step down and trigger an avalanche that releases in deeper layers. Search out stiff-feeling snow, smooth, pillowlike features, or wind-textured surfaces as you gain elevation and change aspects. Simple tests can help you evaluate the bond of slabs to the layer below. Don't ignore obvious signs of instability like shooting cracks and whumphing. 

    (2/12/2025)

    Wind-effect in Canyon Creek. Identify textured surfaces as obvious indicators that a wind slab may be present here or nearby. 

Avalanche Discussion

Prior to Friday, fresh, reactive slabs formed. Many of these were small. Avalanche danger mainly exists in areas with newer wind slabs, although some of these slightly older slabs might still react to a human trigger. For several reporting parties, slabs were reactive enough to warrant avoidance. Deposits were shallow and in pockets where you could mainly identify them and navigate around the drifts. A few natural avalanches were observed as well. As you climb higher in elevation, you can expect more wind slabs that could react to a human trigger. 

As expected, many wind-affected surfaces exist. Light, dry snow can still be found on sheltered, shady slopes. Crusts exist on steep, sunny slopes, which may be buried by a thin coating of new snow. Faceting, or weakening of the snow surface has happened in the last week, in addition to surface hoar development. It's safe to assume that many windward slopes had much of the weak snow at the surface scattered or destroyed by the wind. 

Buried weak layers that produced avalanches two weeks ago have trended more resistant in testing and less likely to propagate. Also, no human-triggered avalanches - that were suspected of releasing at either the 1/31 or 1/10 interfaces - have been reported since Sunday, February 2nd.  The layering in question can be found between 1.5-4' deep where the top layers of snow meet a crust or denser layer, but harbor a sneaky weak layer at the interface. We may see more action from these layers as fresh snowfall in the forecast adds additional load, possibly by the end of the day on Sunday. 

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