Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Daytime warming will drive avalanche conditions, increasing the chance of cornice falls and wet avalanches. Falling cornices could have surprising results including triggering very large avalanches. Keep timing and overhead hazards in mind, and be ready to move to shadier and lower-angle terrain as temperatures heat up. 

Problemi valanghivi

  • Loose Wet

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

    Expect conditions to become more dangerous as the day warms. Look for rollerballs, tree bombs, and feel for heavy wet snow as indicators that the danger is increasing. Slides may become large on steep or rocky slopes as the day progresses and warming continues to break down the crusts in the upper part of the snowpack. Time your day to stay off of steep, sunny slopes as they get wet and weak. 

    (3/17/2023)

    Two wet avalanches, up to size D1.5, in the neighboring West North zone.

  • Cornices

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

    With ongoing warming, keep an eye out for anomalous events like cornice fall and even glide avalanches. Cornices can fall without warning and can have unexpected consequences, including triggering very large avalanches. They can break further back than anticipated. When traveling on ridges, make sure to stay well away from the edge and look for clues like rocks or trees sticking out of the snow to indicate places that are not overhung snow. Stay out from under cornices and be sure to only stop and re-group in areas free from overhead hazards.  

    (3/16/2023)

    Cornice fall over a recent skin track in Cutthroat drainage observed on Thursday morning.

    Photo: Ryan Minton

Avalanche Discussion

On Saturday, observers reported lots of snow falling from trees and small wet avalanches on steep, southerly aspects. Significant snowfall and intermittent wind events since late February added about 3ft to the snowpack. The current warming trend is changing the snowpack and has caused over a foot of settlement in less than a week at Washington Pass.

Three very large natural avalanches ran around the 14th above treeline; A D3 on an east aspect in Cutthroat Creek, and two D3s on  Big Kangaroo Peak, one on the northwest aspect and another on the northeast aspect into Willow Creek. These ran beneath large rocky cliffs. The slide in Willow Creek appears to have run down to the ground at a moraine, with a crown easily 3-6ft deep, possibly up to 10ft. 

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 this crust. It's suspected to have been a weak layer for some of the very large avalanches at the end of the last storm cycle. If you're motivated to dig deep enough, you can probably still find the January 5th surface hoar. We have less of an understanding of the progression of these layers east of Mazama and the Twisp River drainage.  

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