Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can trigger avalanches near and above treeline where the wind drifted slabs. You may still be able to trigger small avalanches on steep slopes below treeline where you find weak, soft snow on the surface. For Friday, expect light precipitation in the morning with warming temperatures throughout the day.

Problemi valanghivi

  • Wind Slabs

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

    You can trigger large avalanches on leeward, wind-exposed slopes. Gusty southwest winds transported snow and formed thick slabs on Tuesday night and again Thursday eveneing. Signs of wind slab instabilities are shooting cracks, whumphing collapses, and recent slab avalanches on leeward and cross-loaded slopes. Avoid convex rolls in the terrain or unsupported features where you find recently drifted snow. Use caution on slopes steeper than 35 degrees where you find drifted snow, wind features, and overhead cornices. You may still be able to trigger fresh cornices. Give these a wide berth as they could break and trigger large avalanches below. 

    Example of intense wind loading off a ridgeline.

  • Loose Dry

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

    While avalanches below treeline are generally unlikely, theres a chance you may be able to trigger them where you find soft uncohesive snow on the surface. The snow stayed relatively dry in the upper reaches of the below treeline band or above about 5,500ft. Use test slopes and snowpack tests to check if the snow slides easily. Use caution around very steep slopes and near terrain traps (gullies, cliffs, and rocks) where you find signs of instability. Consider avoiding convex roll-overs and unsupported features, like pillows,  which will be easier to trigger than planar, supported slopes.

Avalanche Discussion

Expect light precipitation Thursday night into Friday morning on Washington Pass. While temperatures will warm, precipitation should mostly be snow. Very little snow will make it to Mazama or further down the valleys. 

From January 11th to 13th a major storm limited travel and observations at upper elevations. Very large and destructive avalanches ran through entire avalanche paths. The avalanche cycle occurred on the night of the 12th. Observers reported avalanches at least to  D3 in size (big enough to break mature timber and bury cars) including an avalanche that hit a closed portion of Highway 20, below Delancey Ridge. This avalnache ran over 3,000ft and formed debris piles that were 9 feet deep in places. With observations and travel limited by the intensity of the storm, we still have uncertainty, around what's happening at upper elevations.

From weather station data, Harts Pass received 2.7" in water equivalent, half of which likely fell as snow after the rain event at 6500ft. The Washington Pass weather station gained 2 feet of height of snow, even with the rain event, and similarly logged at least 1 foot after the shift back to snow on Tuesday night.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources. Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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