Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

Very dangerous avalanche conditions exist with heavy snowfall and rising temperatures. Natural avalanches are expected to run, and some of these may be very large. Stay off of, and out from underneath steep slopes on Tuesday and Tuesday night.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    Heavy snowfall with warming temperatures will create instabilities in the new snow. Most storm slabs occur during the storm, and it will be storming on Tuesday. Signs of instability are shooting cracks and recent slab avalanches. These may occur even on small, steep features and could be 12" deep below treeline. At higher elevations slabs could be up to 2ft deep during the day tomorrow, and growing rapidly. Tuesday is a good day to plan to avoid avalanche terrain altogether, staying well away from any steep slope.

    In addition to storm slabs on the surface, deeper weak layers exist in areas with a shallow snowpack such as the Winthrop foothills, and the lowlands around Twisp. Any storm slab or loose wet avalanche could step down to these old weak snow layers and create large and destructive avalanches in unusual locations. 

    Example storm slab

  • Loose Wet

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

    Wet loose avalanches may become a problem by the afternoon at low elevations, with snow turning to rain. These could run on steep slopes and could easily be large enough to bury and kill a person. Signs of wet loose instability include rollerballs, wet sticky snow over dry snow, and recent fan shaped avalanches. Avoid going underneath steep slopes, even if it's on a trail through the trees as wet loose slides could run through open forested terrain. 

    Example loose wet avalanche.

Avalanche Discussion

Heavy snow should begin to add up quickly in the Methow and surround valleys. With warming temperatures and very strong winds into Tuesday night, one could expect a significant avalanche cycle. This is essentially a two day event, with things winding down on Wednesday.

Near Washington Pass, the snowpack is deep, strong and avalanche concerns are limited to recent snow and wind events. However, in the eastern part of the zone the snowpack is more shallow. Here, persistent weak layers may be found near the ground, and we may get enough new snow for these to become problematic in the next day or two. Last week, an observer near Aspen Lake reported an avalanche on old, weak layers beneath the recent storm snow, whumping collapses, and propagating test results. In areas like the Winthrop foothills, the lower Twisp River, the Lost River drainages, and areas east of Mazama the snowpack may be shallow and weak. If you're venturing into these eastern mountains, expect a weak and dangerous snowpack that could become reactive on Tuesday.

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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