Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Wet avalanches are the main hazard for the next few days. Reduce your exposure to large cornices and glide cracks. Avoid travel on or below steep slopes if the snow is wet, soft, and unsupportable. Small avalanches in dry snow should be on your radar anywhere you find more than a few inches of new snow and signs of wind transport.

Problemi valanghivi

  • Loose Wet

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

    Continued warm temperatures and increasing sun will keep wet avalanches in play until temperatures cool. You are more likely to see wet avalanches on slopes facing the sun but shaded slopes have warmed enough you might see them on those aspects as well. Lots of slopes have produced wet loose avalanches but that doesn't mean there can't be more.

    They are more likely to occur when the snow is wet and unsupportable. You might even trigger one on a steep slope.  Wet loose avalanches commonly initiate in rocky or treed terrain. Keep an eye on what is above you and limit time spent below slopes where you suspect or witness signs of wet avalanche activity.

    Example of a wet loose avalanche starting in steeper terrain above. Snoqualmie Pass in April 2021.

    Photo: Ian Nicholson

  • Glide Cracks

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2–3

    Glide avalanches, wet slabs, and cornice fall all become hazards during extended periods of above freezing temperatures. The likelihood of seeing one of these avalanches is low but the consequences are high if one occurs above you. In addition to being large and powerful, they can also trigger larger avalanches in much deeper layers.

    Limit travel below large cornices, definitely don't have lunch under one. Also, be on the lookout for glide cracks where the entire snowpack is beginning to slide on the ground below. There isn't much you can do about these types of avalanches other than stay out of the way.

    Note the yawning glide crack where the slab (aka the entire snowpack) is slipping on the smooth rock. Also, look for a "wrinkled" looking snow surface where the gliding slab is pushing on the snowpack below.

Avalanche Discussion

Wet loose avalanche activity was observed in West North and Stevens Pass in the last 24 hours. A very large natural avalanche was reported from Bedal Creek that occurred Saturday afternoon or Sunday Morning. Information is limited but it was large enough to gouge out a track low in the valley. On Saturday, backcountry travelers on Palmer Mountain reported wet loose avalanche activity on upper-elevation slopes in the sunshine.

While the North Cascades stayed mostly dry Monday, precipitation amounts increased traveling farther south in the Cascades. Weather stations in the southern portion of West Central picked up 0.3-0.4" of precipitation as rain below treeline and probably near treeline as well. Dry-ish new snow likely fell at upper elevations.

Monday was the fourth day with temperatures continuously above freezing. This shift in conditions also requires a shift in mindset. While dry snow avalanche problems like storm and wind slabs will still be with us, warming-related avalanche problems should be a consideration any day it’s not cold and stormy. 

Glide, cornice, and wet slab avalanches are just straight-up difficult to forecast. The setup for these avalanches to occur - prolonged warming, glide cracks, and sagging cornices - is coming together. If you see one of these it will probably be large and deadly to anybody in the way. But determining the likelihood is a near roll of the dice. Despite Moderate danger at all elevations, you may see zero avalanche activity or you may see a D3 triggered by cornice fall. Don’t be surprised by either outcome.

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