Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

Dangerous avalanche conditions remain after a wet and windy storm that brought a widespread avalanche cycle on Tuesday. You can trigger large avalanches near and above treeline where the wind drifted thick slabs. You may still be able to trigger avalanches below treeline where you find either entirely dry snow or wet, weak snow.

Problemi valanghivi

  • Wind Slabs

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

    You can trigger large avalanches on leeward, wind-exposed slopes. Strong southwest winds transported snow and formed thick slabs on Tuesday night into Wednesday. Signs of wind slab instabilities are shooting cracks, whumphing collapses, and recent slab avalanches on leeward and cross-loaded slopes. stay off of slopes steeper than 35 degrees where you find deeply drifted snow, wind features, and overhead cornices. Cornices may be large and easy to trigger. If you do get up onto a ridgeline, give these a wide berth as they could break and trigger very large avalanches below. 

    In addition to slabs on the surface, deeper weak layers exist above 5,000ft in areas with a shallow snowpack, such as the Wenatchee Mountains. Any avalanche could step down to these old weak snow layers and create dangerous and destructive avalanches. 

    Example of intense wind loading off a ridgeline.

  • Loose Wet

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

    At low elevations, you may find an entirely weak, wet snowpack. You may be able to trigger avalanches where you sink into wet snow up to the top of your boots. Avoid slopes 35 degrees and steeper where you find wet, weak snow, especially where the snow is unsupportive and collapses under your weight. As you move higher in the mountains, you'll find that snow surface is firm and supportive. In these areas, it will be difficult to trigger avalanches. 

    Deeper weak layers exist in areas with a shallow snowpack such as the Wenatchee Mountains. In these areas, you could trigger a dangerous persistent slab or wet slab avalanche on old snow near the ground. These would be difficult to manage, could be triggered from a distance. It's best to give avalanche terrain a wide berth on Thursday in areas with a previously shallow snowpack. Wet slabs are difficult to predict and can be unmanageable.

    (1/13/2021) Wet avalanches on Granite Peak in the neighboring Snoqualmie Pass zone. [Photo: Charlie Hagedorn]

Avalanche Discussion

From January 11th to 13th a major storm limited travel and observations at upper elevations. Large and destructive avalanches ran, though observations are limited. Backcountry travel has been limited by the intensity of the storm and the amount of recent snow, rain, and wind. All of this leaves much uncertainty, especially around what's happening especially at upper elevations. With uncertainty around the likelihood of avalanches at upper elevations, it's best to approach avalanche terrain cautiously and make conservative terrain choices. 

A widespread avalanche cycle occurred on the 12th. Observations have been limited but in adjacent zones, the activity has been well documented. I was on Stevens Pass, on Tuesday and every avalanche path I could see had at least one, if not multiple avalanches in it. On Washington Pass, observers reported avalanches up to D3.5 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. 

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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