Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Updated 6:00 am: Wind Slab Avalanche Problem added due to increased winds overnight.

Deep persistent slabs could avalanche with your added weight in isolated areas. They are getting more difficult to trigger, but if you do trigger one, expect catastrophic results and you will most likely die. Assess the weak layer with a snow pit before considering exposing yourself to open slopes greater than 35 degrees.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Soft, fresh wind slabs that may react to a human trigger developed Thursday night.  You will find them at higher elevations, and they will probably remain small in size, but could have enough mass to knock you off your feet or take you for a ride.  These avalanches might add enough weight to trigger an avalanche in the underlying deep persistent slab, resulting in a very large and deadly avalanche. 

    Search the snow surface for signs of wind deposits, like textured snow or drifts around objects.  Feel for snow becoming stiffer beneath you.  When you notice drifts or find the snow feels different, use these observations to anticipate nearby wind-loaded terrain. If you suspect a wind slab exists on a feature, seek out less wind-affected or lower angled slopes. 

    Small wind slabs could react to a human trigger on leeward slopes.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    You could trigger an avalanche on a deep persistent layer which is buried 4-6 feet down. The layer is progressively more difficult to trigger as time passes. At the depth this layer is buried, it is unclear whether the sole weight of a person would cause an avalanche unless they found a shallower spot, which is possible. A snowmobile could easily trigger it at that depth. If an avalanche does occur, it will be very large and you will probably not survive. 

    For this avalanche problem, there are no obvious signs of instability like you might find with other problems. You need to dig down to the Jan 13 crust and make note of the layer above it, observing the presence of persistent grains and how readily that layer fails. Broad open slopes and large features in areas steeper than 35 degrees is where you are most likely to find the weakness, so avoid those slopes unless you have investigated the strength of the weak layer. If you must get on steep slopes, your best option is to travel on slopes that you already know slid on that layer.

    (2/6/2021) This slab was intentionally triggered by a cornice drop in the West South zone on Saturday. It propagated widely and is believed to have run on the Mid-January crust/facet combo. It is not unlike what we are seeing here in the West North zone. [E aspect, 6300'. Photo: Jeremy Allyn]

Avalanche Discussion

Shallow wind slabs may have developed in lee areas along ridgelines and around features at higher elevations in the last 24 hours. Search for active signs of loading, like blowing snow, and feel for deposits of firmer snow to avoid on steep slopes. Small loose avalanches could also occur. Either of these might catch you and take you for a ride, or could add enough weight to trigger the deeper slab, resulting in a very large avalanche. 

Unfortunately, a snowbiker triggered an avalanche on the deep persistent layer in the East Central zone on Monday, and was buried and killed. The Accident Reports page provides more details about the incident. You can also see the short video about it in the media gallery below. Avalanches failed on this layer in nearly all of the forecast zones in the Cascades in the last 2 weeks, and a number of them involved people. Recently the avalanche count has slowed, but the layer is still lurking.  Make your decision to travel out on a steep slope based on solid evidence, because the risk versus reward is not worth the consequence of not making it home at night. 

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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