Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Complicated conditions require a simple approach to reduce risk:  avoid traveling on or below big and steep slopes that could produce large avalanches. Don't get caught off guard by smaller loose snow or slab avalanches in seemingly less threatening terrain.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Large, somewhat atypical avalanches, signs of instability, and a poor snowpack structure are the signs and symptoms of a persistent slab avalanche problem. A weak upper snowpack that developed during the January drought is now struggling to support the three feet or more of new snow that’s fallen since Friday. 

    These types of avalanches are tricky. Snowpack structures vary across the forecast zone or even across the same slope. Big triggers like a snowmobile or group of people could trigger an avalanche where the weight of a single person will not. These avalanches could propagate widely, release in adjacent terrain, from the middle of or even below a steep slope.  What’s most frustrating is a handful of big slopes cold produce large, dangerous avalanches, while most others are relatively stable. But it’s hard to exactly pick out which ones will and which won’t release.

    Don’t ignore signs of instability. But don’t assume there is no issue if you don’t experience whumphing, or see shooting cracks and recent avalanches. Digging a pit on one slope may or may not be relevant in assessing a different slope. The best way to reduce risk is to avoid traveling on, adjacent to, or directly below big and steep slopes that can produce one of these avalanches.

    (2/3/2025)

     Avalanche control work on Monday morning produced this large slab avalanche.  The crown was estimated to be around 4' deep. It likely failed at the old-new interface or a crust-facet combination a bit lower. 

    (SS-AL-D2-O)

    Photo: Mount Baker Ski Area

  • Wind Slabs

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

    Look for fresh wind slabs, mainly in the eastern and northern portions of the forecast zone. While high wind speeds are not forecast, it won’t take much to get soft snow at the surface to drift onto leeward slopes. A small avalanche can also trigger a bigger one that releases in deeper layers of weak snow.

    Active drifting will show you which slopes are loading up. Textured or scoured snow surfaces and cornices will point towards slopes holding freshly wind drifted snow if the wind isn’t blowing. You might be avoiding big, steep open slopes due to danger from larger avalanches, but could still find wind slabs on smaller terrain features.

    (12/29/2021)

    Use wind eroded surfaces to figure out where wind slabs may have formed.

     

  • Loose Dry

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

    There’s no shortage of loose unconsolidated snow out there. If you do push onto steep slopes expect to get some snow moving down the hill with you. The biggest risk might be in lower elevation terrain where there are numerous creeks, rocks, and other low snowpack hazards to get dragged into. Look for loose snow avalanches below cliffs, especially if the sun comes out and gets some snow to shed onto the slopes below.

    (2/26/2023)

    Small loose snow avalanches can still push you around in sheltered terrain with creeks and other hazards below.

    Photo: Zack McGill - Cascade Mountain Ascents

Avalanche Discussion

The long stretch of dry, generally cooler weather in January left us with a parting gift of weak snow, which is now well buried and has produced natural and human-triggered avalanches up and down the west slope of the Cascades. While the snowpack setup is different between avalanche forecast zones - and even varies within individual zones - the story is the same. It will just take longer than usual for the slabs of new and wind drifted snow to stabilize. With a lack of recent observations from the West Central zone, it's recommended to check the avalanche forecast for the zone nearest to where you are heading into the mountains. For instance, if you are going to be along Hwy 2 then look at Stevens Pass. 

In addition to avalanche danger, deep new snow also brings the risk of snow immersion. Keep your partners in sight or at least be able to communicate at all times. 

Regioni coperte