Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Avalanche activity will increase throughout the day as we get more precipitation. Slabs of dry snow at higher elevations are likely to avalanche with a human trigger. Lower down, the snow has seen plenty of rain, and wet avalanche activity may continue. Avoid steep slopes at all elevations, and if you notice any natural avalanche activity, steer around lower-angle slopes beneath large avalanche paths. 

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Avalanche danger will increase throughout the day. We're forecasted to receive up to a foot and a half of snow overnight through to the end of the day Monday. If we get more snow than forecasted, or conditions are more reactive, take a step back and reevaluate.

    Dry snow will form fresh new slabs at mid and upper elevations. You are most likely to trigger one of these avalanches in wind-loaded terrain. However, changes in temperature or snowfall intensity can create instabilities in wind-protected terrain as well.

    Most areas should see moderate snowfall and wind speeds. Schreibers Meadows and the Baker backcountry may see the most snow, strongest winds, and greatest avalanche danger of anywhere in the zone due to the southerly influence of this storm. 

    Track the depth and distribution of new and wind-drifted snow over the old surface below. You can evaluate how well new slabs are bonding with simple tests like slope cuts, skin track tests, and hand shears. At some point, new snow depths may grow deep enough that these tests will no longer be representative of weaknesses. Blowing and drifting snow will show you which slopes could be wind-loaded. Stick to more sheltered, lower-angled terrain to reduce uncertainty during stormy conditions.

    Example photo: a Storm slab avalanche, similar to one you might trigger on Monday. 

    Photo: Irene Henninger

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Rain has fallen at mid and lower elevations since Friday. Depending on where you are in the zone and your elevation, water may have saturated well over a foot into the snowpack. Natural wet avalanche activity mainly occurred on Friday and Saturday. Natural activity may continue, but human-triggered avalanches are possible, and could grow to large in size depending on the depths of wetting in the snowpack. For now, avoid slopes greater than 30°. If you notice natural avalanche activity or have any doubt, avoid traveling in runouts beneath steep slopes as well. 

    There's a chance that glide avalanches could occur on steep, smooth, rock and shrubby surfaces. If you notice glide cracks, steer clear of slopes beneath the cracks. After several days of moisture percolating into the snowpack, wet slab avalanches may wake up. We've got a lot of uncertainty about whether this may happen, but keep it on your radar during your outing. 

    (1/20/2024)

    Large wet loose avalanches which likely occurred Friday or early Saturday in the Baker backcountry. We don't expect as much wet avalanche activity as there was earlier in the rain event. 

    Photo: Julz Holder - Grounding Truth

Avalanche Discussion

Current avalanche concerns have a lot of grey areas and don't fit perfectly into boxes. Smaller avalanches at upper elevation have a very small chance of stepping down, causing large  dry slab avalanches on any number of layers that we've got concerns about in the top 3-5 feet of the snowpack. We suspect that due to the warm temperatures, any shallower instabilities in the snowpack will heal quickly, and overall, the snow may be stubborn. You still might find the right spot where you could trigger a large avalanche if you're out in steep terrain on Monday. 

On Sunday, rain and moist conditions went a little higher in elevation than we thought they'd go. We received reports that moisture saturated much deeper into the snowpack. Runnels were reported as forming by multiple parties. Not as much natural avalanche activity was seen as in the previous few days, but small human-triggered avalanches occurred. Expect more of the same, but possibly larger human triggered avalanches, both wet and dry, on Monday. While not a major concern, deeper slab avalanches show that there are still less than bomb-proof layer interfaces above the 12/30 crust. It just takes a really, really big trigger to get one of these slabs moving. 

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