Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Natural and human triggered avalanches in steep, wind loaded terrain were reported from other zones Sunday afternoon. Similar avalanches will be slightly more difficult to trigger Monday but still pose a significant hazard to backcountry travel. The safest plan is to just avoid steep slopes you suspect hold wind drifted snow .

Problemi valanghivi

  • Wind Slabs

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

    There is a good chance that wind slabs from the latest storm will be hidden by at least a few inches of snow falling with no wind. In some places wind slabs formed over the old snow surface of weak facets and/or surface hoar that could make slabs easier to trigger and also delay stabilization.

    • Look for signs of wind affected snow like scoured ridgelines, fresh cornices, and smooth drifts to figure out the wind loading pattern in the surrounding terrain. Shooting cracks mean you found reactive wind slab.
    • Keep track of differences in how much light snow you are moving through vs. how stiff the snow feels underfoot. Deeper snow and softer layers below likely equal less wind effect while stiffer snow underfoot is probably wind slab.
    • Take a few minutes to look for and assess facets or surface hoar that could be at the old/new snow interface. 
    •  Test slopes and other assessment tools can help you evaluate the bond of wind slabs to the layers below.

     

    (2/26/2023)

    A small, remotely triggered wind slab on a south aspect in West North @ 4700', triggered from where the two skiers are standing. There was a noticeable collapse when it released and facets were found in the bed surface.

    Photo: Jason Speer - Baker Mountain Guides

  • Loose Dry

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

    There is no shortage of light, fresh snow out there. Many small, human triggered avalanches - somewhere between dry loose and very soft storm slabs - were reported from steep, wind sheltered areas. They are probably not big enough to bury you but the outcome could be different with terrain traps in the runout or on big steep slopes where they can run far and entrain more snow.

    These kinds of avalanches shouldn’t take you by surprise - move slowly over steep rolls in wind sheltered terrain and stay alert to the amount of snow moving with you when descending.

    (2/26/2023)

    Human triggered dry loose avalanche in Swfit Creek just outside of the Mt. Baker ski area boundary.

    Photo: Zack McGill - Cascade Mountain Ascents

Avalanche Discussion

Snowfall will continue in parts of the West Central as convergence zone snow showers pick up with a wind shift to the west.  With this type of post-storm pattern one area might see several inches of new snow while there might be none a few ridges away. Be ready to assess danger form additional snowfall overnight, especially around the Mountian Loop. Showers should end by morning before light snowfall returns later in the day.

A few hours of decent visibility allowed for observations of a handful of natural avalanches to D2 in West North It also got some folks out onto steep, wind loaded slopes where they triggered slab avalanches up to D2 in size. No one was reported as caught or injured. Reported avalanches were on north through east facing slopes near treeline. Most occurred just below ridgeline but some were found mid-slope in cross-loaded features.  Reported avalanche activity in other zones was limited to small but fast-running dry loose and slab avalanches.  

West Central met expectations for snowfall with the latest storm dropping 12-16" of new snow with strong winds persisting through the day near Darrington. Similar conditions were found in West North with 12" at Stevens Pass and even less at Snoqualmie Pass. Steady, strong winds created a highly variable pattern of accumulation with 0”-24” on the ground depending on the aspect in relation to wind. Outside of wind affected terrain the new snow lacked significant cohesion and released as very soft slabs or sluffed easily

 

 

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