Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Snow and avalanche conditions vary extensively between upper elevations, where dry snow fell, and lower elevations, where the recent precipitation fell as rain. Avalanche danger will increase as you gain elevation, and change from wet snow to dry snow problems. At higher elevations, avoid new snow deposits deeper than about 6 inches, especially if stiffer snow sits over fluffier snow, on steep slopes. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    New snow avalanche problems at upper elevations are your largest concern, where it's likely you can trigger an avalanche. We're forecasted to get around 6 inches overnight, and then another 6 inches or so during the day up high.  As the majority of the snow falls, strong winds will blow. The most reactive slabs will probably be in wind-loaded areas. However, towards the end of the storm we'll get a slight rise in freezing levels. Even non-wind-loaded areas may have slightly heavier snow over lighter and dryer snow, which means it's formed an "upside down" snowpack. Avalanches are more likely to occur in those snow conditions. Winds will reduce as snowfall tapers, and any wind slabs may be sneakily hidden by less wind-affected snow. Beware of light, dry snow that has a firmer, wind-affected layer hidden beneath it. 

    Constantly evaluate the snowpack as conditions will change throughout the day. Be on alert for bulls-eye clues, or red flags, as your most obvious indicators to avoid steep slopes. Even if you don't see any of these signs, you could still trigger an avalanche on a steep slope. The new snow will probably be less than 2 feet deep except in deeper drifts, so you can easily dig down to evaluate the bonds with the underlying layer. Pay attention to hollow-feeling snow, or wind drifts around features, in gullies, or along ridgelines. Avoid slopes greater than 30° with more than 6 inches of new snow, but especially if you notice any "upside down" characteristics of heavier snow over lighter, fluffier snow. 

     

    Example photo:  A storm slab with slight wind influence avalanche that occurred at the Baker NRA last year. You can expect something similar to this to occur on Thursday. 

    Photo: Irene Henninger

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    A rain-snow mix at mid-elevations, with rising temperatures during the day, means that we'll probably see wet loose avalanche activity in the new snow layer. Freezing levels will rise during the day, so wet avalanche activity could creep higher as freezing levels inch upwards into previously dry snow.

    We expect most slides to remain fairly shallow, only impacting the top 6 inches or less, with avalanches mainly limited to the new moistened snow. There's a chance they could run a little deeper. Lower down, expect the snowpack to be wet and punchy. There's less of a chance that an avalanche will occur in the old snow layer that only saw rain, but small amounts of shedding could still occur. 

    If you see rollerballs or small avalanches, avoid similar slopes that are steep and travel quickly beneath them. 

    Example photo: Moist conditions in new snow caused rollerballs in the new snow. This is similar to initialy avalanche activity you can expect to see Thursday.  Bearpaw area. Photo: Andrew Kiefer

Avalanche Discussion

This new snow layer comes after a large storm that began Christmas day, producing more than 2 inches of water. This likely fell as around 2 feet of snow at upper elevations. There's still a small chance that an avalanche could fail underneath the Christmas storm layer, although a couple of days since the storm has likely improved stability. The Christmas storm came with wind gusting into the 50's for the majority of the precipitation. We continue to squeeze the most precipitation of the Cascades out from the passing weather systems here in the West North zone, which is not a huge surprise. 

Lower elevations up through part of the mid-elevations have a moist to wet snowpack that's predominantly seen rain in the last week+. Snowlines have consistently been shrinking for weeks now, and consistent snow cover doesn't start until about 3500 feet, or even higher on south-facing aspects. There are open creeks, and thin snowpacks with rocks and trees poking through the snow or just barely covered. Upper elevations have a few feet of snow over a crust from the start of this month, but we're not sure how high in elevation that crust exists. If you get out, and especially if you make it to upper elevations, send us an observation.  Our information is very limited from up high. 

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