Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
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

As this stormy period intensifies, avalanche hazard will continue to rise. As you ascend in elevation, avoid wind-loaded features where it may be easier to trigger an avalanche. Using small test slopes to look for cracking or failing blocks of snow can help you identify slab potential.

Problemi valanghivi

  • Wind Slabs

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

    Snow showers and more wind are expected on Friday. Due to a flip-flopping wind direction, shallow slabs could exist mid-slope or on a variety of aspects - including ones where you're not used to finding them. Use visual clues such as new cornices, actively blowing snow, or textured surfaces to help identify problematic slopes. You can then seek out features containing pillow-like drifts to steer around. Wind slabs like to form near ridgelines, rocky chutes, the base of cliffs, or on convexities. On some slopes, they may have formed over a firm crust, giving them a good sliding surface.

    (12/12/2024)

    Fresh drifts and cornices along a ridge are bullseye information that the wind has been moving snow and wind slabs may exist on leeward slopes.

    Photo: Josh Lipkowitz

Avalanche Discussion

Enter day two of our active weather pattern: More wind (but from a different direction) and more snow showers. This storm track has slowly increased the avalanche potential in our zone and will continue to do so into the weekend. The main event is on tap for Friday night into Saturday, and will likely focus on the volcanoes. More on that tomorrow. 

On Thursday, NWAC forecasters visited the Crystal Lakes area and found that it got hammered by the wind. Variable surface conditions included the spectrum - firm crusts, wind skins, sastrugi, breakable crust, and pockets of soft snow. Crystal Pro Patrol reported shallow wind slabs reactive to ski cuts during their morning mitigation efforts. With wind speeds as high as 60 mph recorded at the top of Crystal on Wednesday night, it's no wonder. Further south along the crest, White Pass Pro Patrol reported actively blowing snow due to stiff winds, particularly in the morning. 

These observations leave us wondering how much snow is still available for transport. Observations from earlier this week paint a picture of wind-textured surfaces throughout the volcanoes and crest, but plenty of well-settled dry snow on shaded aspects. Weather station data suggests that Crystal may have been a slight outlier in terms of the wind strength on Wednesday night. The hunch is that we're not done transporting snow yet within the West South plus new snow is on the way, particularly for the volcanoes.

As alluded to above, the snow surface is now quite variable throughout the zone. However, the structure remains fairly uniform. We do not have any major layers of concern below the 12/7 interface that formed during last weekend's rain event. This easily identifiable crust is a foot or less below the surface. Any avalanche activity in the coming days should be confined to the snow above it. An interface just above the 12/7 has been highlighted in snowpack tests recently, so we'll keep an eye on it heading into the weekend.

This storm will likely help our early-season conditions down low, but not fully eliminate them. Watch out for shallowly buried or exposed rocks, creeks, holes, and logs.

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