Bollettino valanghe

West Slopes South

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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In sintesi

On Saturday, keep an eye on how the weather is affecting the snow surface and driving the avalanche hazard in your location. If you are not standing on a firm crust, but rather in soft and wet snow, consider avoiding steep sunny features. In areas prone to cool east winds, the surface may have a harder time softening, keeping avalanches at bay.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Warm and sunny weather will again battle cool easterly winds in an attempt to destabilize the snow surface on Saturday. This may be difficult to achieve near the crest where east winds will be stronger, or first thing in the morning due to an overnight freeze. However, as the day wears on, watch the snow surface to see if it becomes soft and moist. If it does and you are sinking into the damp snow past your ankle or notice fresh rollerballs and pinwheels, then it’s time to start thinking about Wet Loose avalanches. These slides often start at a point, frequently initiating near trees or rocks, can entrain additional snow, and fan out as they descend downhill. You will be more likely to trigger them once the snow is “ripe” on slopes over 35 degrees that see direct sunshine at mid to upper elevations. Your best mitigation strategy will be to head for lower angled or shadier terrain away from overhead hazards.

    (2/9/2022)

    Triggered rollerballs on an E-facing slope. This is a great sign that the snow surface is becoming wet and unstable. 

    Photo: Andy Harrington

Avalanche Discussion

The West South is in the midst of yet another warm spell with NWAC weather stations around the zone recording temperatures in the 40s and 50s. Although the weather may seem similar to the last warm-up, there are some differences you need to take into account if you are heading into the mountains on Saturday. Unlike a few weeks ago when our warmup coincided with a firm rain crust, much of the zone currently contains several inches of settled storm snow atop the Late January Crust. This snow is still in a state of transition toward a more springlike snowpack in many areas. It is gaining strength from the top-down as it goes through freeze/thaw cycles but is capable of producing avalanches when the right conditions are met. On Saturday, reaching those conditions will be a question mark in some areas of the zone due to the cool east winds. Regardless of your location, you should find variable surfaces based on aspect and elevation, with a mix of ice, breakable crust, and spring-like snow. These surfaces should be softer in the afternoon, but you will need to watch the weather and conditions to see if they reach the tipping point for avalanches in your location.

The depth of the Late January Crust is variable across the zone but can be found up to a foot below the surface in some locations. The weak snow found at this interface in a “facet-crust sandwich” has not produced any avalanches in our zone to date, but we will continue to watch it throughout this warm-up. We suspect that all avalanche activity should occur in the snow above this easily identifiable layer, where multiple other recent crusts should have developed in recent days. This includes the possibility of cornices collapsing due to the warm weather. Be sure you choose travel routes that put plenty of space between you and these ticking time bombs.

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