Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

With warmer temperatures and ample sunshine, small wet loose slides could become common on most steep slopes. In high, exposed places you could still trigger a small, soft wind slab on steep or unsupported slopes. You might still be able to trigger a larger and more surprising slab on deeper layers at upper elevations with large loads like cornice fall, or snowmobiles. 

Problemi valanghivi

  • Loose Wet

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

    4-6" of new snow resting on a sun crust makes a good recipe for loose wet avalanches.  Loose slides could occur naturally as the snow surface becomes moist with sunshine and daytime warming. Watch for roller balls and tree bombs as indicators that the snow is becoming moist. For the most part, these should be small, but in larger terrain they could entrain more snow than you'd want to mess with. If its not the sun and warming that does it, small dry sluffs could be triggered on steep slopes in the shade. For both of these, you'll want to exercise caution near terrain traps like slopes above cliff bands or tight gullies where a slide could push you somewhere with increased consequences.

    Example loose wet slides from the West South zone earlier this week.

    Photo: Andy Harrington

  • Wind Slabs

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

    Small, soft slab avalanches could remain possible on Wednesday. You're likely to find these at upper elevation where more snow fell, and wind transport was active through the day on Tuesday. Look for drifting patterns and textures, and feel for slightly stiffer snow as you gain elevation. Look for signs of instability like cracking  and use small test slopes to check for instability.  Steer around drifts on steep and/or unsupported wind drifted features.

    Be aware that cornices have gotten quite large and have occasionally fallen during recent loading and warming events. Cornices or other large triggers like snowmobiles could potentiall initiate deeper and more surprising slab avalanches. Give yourself a wide berth from corniced terrain and large, steep slopes in the unlikely event that one of these does occur.

    (2/17/2023) Look for blowing snow as an indicator that fresh wind slabs are forming. Photo: Drew Lovell

Avalanche Discussion

We're in store for a slow warming trend. Temperatures and sunshine should begin to have more and more of an affect on the snow and avalanche conditions over the next few days. Observers have reported a couple of small natural and ski triggered wind slabs over the past few days. A small round of wet avalanches up to size D1.5 ran on south aspects with warm temperatures on Monday. Over the weekend, a 2-4ft deep slabs were reported from areas such as Liberty Bowl near Blue Lake Col and in the Hairpin Valley. Many of these ran beneath large rocky cliffs where storm snow deposited more deeply. Significant snowfall and intermittent wind events since late February have added about 3ft to the snowpack. 

Drew spent a couple weeks near Hart's Pass, and reported that concerns were mainly within recent snow, alternating between loose and wind slab avalanches.  Also on Friday, Wille Webster was in the Silverstar area and found up to 3 feet of recent snow since late February. 

The Valentine's crust is 3-5 feet below the surface in the western half of the zone, including near Washington Pass, the upper Silverstar drainage, and Hart's Pass. You can expect to find it closer to the surface at lower elevations and further east in the zone. There have been numerous observations and snowpack tests indicating weak snow and poor structure below the crust. Avalanches on this layer are unlikely. If you're motivated to dig deep enough, you can probably still find the January 5th surface hoar. It's so deep and rounded, that it hasn't been a concern for avalanches in over a month near Washington Pass. We have less of an understanding of the progression of these layers east of Mazama and the Twisp River drainage.  

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