Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

Wind Slabs may develop Thursday night and Friday as strong winds and some new snow impact the West South. This added load could continue to stress our current snowpack, which still needs time to heal after a week-long storm cycle. Look for red-flag signs of instability such as shooting cracks or whumpfing collapses as you travel and default to lower angled terrain when in doubt.

Avalanche problems

  • Wind Slabs

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

    Even though the snow totals throughout the zone have been variable, Friday should be a day where the zone comes back together as one. Winds on Thursday night will be strong enough to transport snow to create fresh Wind Slabs at middle and upper elevations. As Friday morning approaches, winds should downtrend, but may still be strong enough to continue to wind-load features as new snow starts to fall. A switch in wind direction during the forecast period means that you will have to be aware of wind-affected snow on all aspects and to keep your eyes open for unusual loading patterns. Take a look for actively blowing snow, textured snow surfaces, fresh cornices, or smooth pillow-like piles of snow to help identify where Wind Slabs may have developed. Pay particular attention to the sides of gullies, the base of cliffs, and convex rollovers where wind-deposited snow is often found. Triggering even a small Wind Slab could have significant consequences by then triggering larger Storm Slabs in the recent storm snow. Using small test slopes and uptrack tests can help you test the reactivity of recent Wind Slabs, but as a general rule, you should avoid any suspected wind-loaded features greater than 35 degrees.

    (1/7/2021) This slope had multiple Storm Slab fractures on it and may have failed as recently as this past Tuesday. Slopes like this could easily reload due to strong winds and avalanche again.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    We continue to receive reports of recent large avalanches throughout the zone and believe that the possibility still remains for you to trigger one of these slides on Friday. With the aid of fresh Wind Slabs and a bit of new snow, some slopes could finally reach their tipping point. With so much recent snow out there, any triggered avalanche has the capability of traveling long distances and growing large enough to bury or kill you, regardless of where you are in the zone. Hand pits and test slopes will only give you enough information to determine what is happening near the surface of the snowpack. To get the full picture, you will need to dig down to the 1/1 interface. Unsupported slopes, convex rollovers, and wind-loaded terrain are areas where starting an avalanche is more likely and should be avoided.

    (1/7/2021) This very large natural slide now has fresh snow hiding its debris, leading us to believe it occurred sometime shortly after the New Year.

Avalanche Discussion

Friday should be another day to continue being patient as we work our way out of a major storm cycle and give the snowpack time to heal. Although the danger has dropped to Moderate, the travel advice, size, and distribution all more closely mirror Considerable danger levels. You need to continue to evaluate the snowpack carefully, use cautious route-finding, and conservative decision making out there. Don’t be surprised to hear about some very large (D3) avalanches occurring over the next few days. Although the water numbers for the entirety of the storm favor the volcanoes, totals after New Year’s Day run fairly evenly across the zone. This means that snow above the 1/1 crust is generally uniform across the zone, with the crust typically found around 80-100cm down from the surface. NWAC professionals on Thursday were in the Crystal Mountain backcountry and found a layer of concern approximately 40cm down, weak surface snow that we will keep an eye on going into Friday, along with the remnants of multiple avalanches as large as D2.5. More potential weak points will be created Thursday night and Friday morning with this quick bout of weather, requiring you to dig down to the 1/1 crust to see what troubles lurk beneath the snow surface in the area you are traveling. As noted above, any triggered avalanche has the potential to entrain snow or step down to grow large and destructive.

Other dangerous conditions may exist on Friday as you travel in the mountains. Creeks are running high at lower elevations, large amounts of snow and branches are falling from trees, and the deep snow creates a hazard due to tree wells and deep snow immersion. Find out more information about deep snow safety HERE.

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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