Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

An incoming storm will renew our concern for Wind Slabs on Saturday. The likelihood of triggering an avalanche should increase throughout the day as wind and snow impact the zone. Identify and avoid features such as convex rollovers or rocky chutes where the wind likes to drift the snow into unstable piles.

Problemi valanghivi

  • Wind Slabs

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

    Wind ahead of the onset of precipitation could drift already in place dry snow into shallow slabs. As the snow starts to fall later in the day, look for these slabs to increase in thickness and become more likely. You might find slabs on a variety of aspects due to an expected afternoon wind direction change. Regardless of aspect, these slabs will be more prevalent near ridgelines, convex slopes, or rocky features such as the base of cliffs and confined gullies. Using small test slopes can help give you an indication of how the new snow is reacting to your weight. Take a look for actively blowing snow, freshly built cornices, or new drifts to help you identify wind-loaded features to avoid. 

    (1/20/2023)

    A recent Wind Slab avalanche that was observed on Mt. Adams on 1/20. Note its location below a ridgeline and originating at the base of rocks.

    Photo: Paris Gore

Avalanche Discussion

While the hazard level remains at Moderate for Saturday, the problem set and severity of that Moderate rating is different than what you may have experienced on Friday. We anticipate increasing avalanche hazard throughout the day as a storm works its way into the zone. This storm is expected to bring snow and strong winds with higher accumulations expected on the volcanoes and potentially breezier conditions expected near the crest. With the storm expected to continue through the evening hours and into Sunday morning, you might see conditions start to approach Considerable in the evening hours, particularly on the volcanoes or at upper elevations.

Observations from the zone in recent days have been extremely limited, but the new snow should be falling on a variety of surfaces and further increasing the depth over the prominent MLK crust. On sun-exposed slopes, a sun-crust is expected to have formed on Friday, while shadier slopes likely have some weaker surfaces. Where they exist, those weak surfaces could persist and become buried by this storm or could get wiped out by the winds. If it’s preserved, you could see isolated avalanches breaking in some surprising ways such as spanning far distances or wrapping around terrain features. So make sure you take a minute to check the bonding of the new snow to the old surface to see if it is failing easily wherever you’re recreating. Any avalanche should be confined to the snow above the MLK crust (about 1.5 feet below the surface) and the majority should revolve around the incoming storm snow.

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