Boletín de aludes

West Slopes North

Northwest Avalanche Center
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Peligro de aludes

Mon
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Expect to find wind slabs in the top few feet of snow from the last 3 days of stormy weather. You may find drifting in unusual locations, such as down low on slopes, and avalanches could fail 6 inches to 2 or more feet deep. Make sure to thoroughly investigate for wind slabs and any weaknesses in the top few feet of snow before exposing yourself to any slopes steeper than 35 degrees.  

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    On Saturday afternoon we received reports of two separate avalanches on the north side of Table Mountain (north facing, ~4500ft). A small human triggered avalanche occurred in 5 Minute Trees, a slope which already had several tracks on it from the same day. It caught and carried the backcountry rider, burying them to their knees. We’re glad to hear that they got out without injuries. Nearby, a large (size D2+) natural avalanche was witnessed in Blueberry Chutes, and it is suspected that a cornice may have triggered it. Avalanches are most likely to fail on new snow instabilities, but these now may be a few feet deep, and big enough to bury, injure, or kill you. 

    Strong winds in the last 48 hours redistributed the snow into slabs, especially at mid to upper elevations.  As you travel, feel for stiffer snow beneath you. Visualise clues of wind loading such as smooth pillows or textures surfaces. Avoid these wind loaded slopes in areas steeper than 35 degrees.

    (3/6/2021) A small human triggered avalanche in Five Minute Trees (Bagley Basin, north facing, 4500ft) which occurred Saturday afternoon. The person was buried to their knees, and we're glad to hear that they were uninjured.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1

    Snow at lower elevations may not have gotten as wind affected as higher elevation terrain. With well over a foot of snow at lower elevations, storm slab avalanches could occur. Investigate any interfaces in the new snow layers with quick pits before exposing yourself to steep slopes. Use small test slopes to see if you might trigger a slide on it.  Stay off slopes steeper than 35 degrees while this new snow adjusts unless you've thoroughly investigated the new layers.

    Small human triggered storm slabs could occur on Sunday.

Avalanche Discussion

As of Saturday evening, 19 inches of snow (2.5” water) has fallen at the Heather Meadows weather station since Thursday. Far more snow fell at higher elevations. We may see up to another foot by Sunday afternoon. Today was a good reminder that avalanches can surprise you, even on slopes that have already been skied. With considerable avalanche danger, natural avalanches are possible and human triggered avalanches are likely. Take this into account as you travel in the backcountry on Sunday. 

There are layers of concern in our snowpack buried over 10 feet deep, although most  recent avalanches failed on shallower layers in this zone. The new snow load may test the deeply buried weakness, waking it up once again. We last saw it over a week ago, when there was a widespread natural avalanche cycle that resulted in many very large avalanches (D3+), some hitting Highway 20 just outside Newhalem. Several very large avalanches were reported further south in the zone. Our concern, a mid January deep persistent layer is 200 - 300+cm deep in most areas and is hard for a human to trigger. However, a huge sudden load such as a cornice fall or a shallower wind slab avalanche might trigger an avalanche on that layer. 

Snow and avalanche conditions are variable in the West North zone and throughout the Cascades right now. In general, recent storm snow is stabilizing quickly, but very large natural avalanches along the border of the Stevens and West Central zones continue to keep these old and deep weak layers on our minds in this zone as well. Read the West Central or Stevens Pass Forecasts to learn more about it. 

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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