Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Mon
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Out of date — this forecast expired 6 years ago.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

New snow and wind should combine to increase the avalanche hazard throughout the day on Sunday in the West South zone. Pay attention to changing conditions and look for signs of unstable snow such as shooting cracks or whumpfing collapses. If you notice these signs or find there is more snow than you were anticipating, be conservative and dial back your terrain choices.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Look for Storm Slabs to develop in areas of the zone where 8” or more of new snow falls throughout the day. Although the volcanoes are set to receive the bulk of the precipitation, other areas of the zone could be dealing with Storm Slab issues in their own right. These slabs may be more reactive in areas where the wind is able to move any freshly fallen snow around to create deeper and stiffer slabs on leeward slopes, at the base of cliffs, or on the sides of gullies. These avalanches generally trigger more easily on slopes steeper than 35 degrees, convexities, and unsupported slopes. Luckily, there are plenty of inconsequential small terrain features that fit this description where you can test the bonding and sensitivity of any potential slab. If you find reactive pockets of snow or a poor bond, look to avoid similar slopes.

    (12/12/2020) Cracking in the snow as you travel is an indication that the snow has slab properties and is unstable.

Avalanche Discussion

The West South currently contains a stout rain crust (12/9) overlaid by up to 15cm of weak low-density snow. We have some uncertainty on how new snow will bond to the old snow surfaces on Sunday, but we do feel confident that any potential avalanche should not affect snow below the 12/9 crust. Saturday showed us that Dry Loose avalanches were stubborn to trigger but some did run on the 12/9 crust in steep terrain within the zone. Reports from Paradise on Saturday confirmed that snow was being transported by the wind throughout the day and starting to wind load some unusual slopes.

We often talk about making your own observations and adjusting your plan based on what you find and Sunday will be an excellent day to put all that practice to use. Find yourself a nice test slope away from avalanche terrain and take a look at the new snow. How has the snow bonded to the old snow surface? How is the old snow bonded to the 12/9 crust? If you find that there is cohesive snow with a poor bond, then you should avoid slopes steeper than 35 degrees. You could also take a measurement of the new snow depth. Is there more or less snow than you were anticipating? If you find more than 8” of new snow, realize that avalanche danger could be higher than predicted and dial back your terrain choices. If you find light and fluffy snow that is unconsolidated, put Dry Loose avalanches back on your radar. You can also take these observations as you travel by digging quick hand pits to test the bonding and by looking around for actively blowing snow, textured snow surfaces, or smooth pillow-like piles of snow to help you determine if there are pockets of wind-blown snow you need to avoid. With the bulk of the precipitation set to fall during the day on Sunday, we expect the hazard should be increasing as the day progresses, demanding that you stay on top of how conditions are changing around you. On the volcanoes, we could approach dangerous avalanche conditions by the end of the day if we exceed our water numbers.

Recent weather wreaked havoc on the snow in the West South. Firm surfaces abound under the recent fresh snow and many previously buried obstacles have recently reemerged. You’ll need to navigate around numerous open creeks, downed logs, and areas of thin coverage. New snow will help, but realize that these obstacles may be shallowly buried until we have a few more storms come through. Be cautious and give yourself extra time to manage these demanding travel conditions.

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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