Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
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Out of date — this forecast expired 6 years ago.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

If you can venture up through the wet mess that this atmospheric river left us to where the snow is cold and dry on Thursday, you have my respect and you should look out for dangerous avalanche conditions due to windblown snow. The mountains will look very different from when you last saw them and you should be prepared for dynamic conditions by easing into terrain and steering around those wind affected slopes.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    The winds were cranking all around the West South as we said goodbye to the atmospheric river event on Tuesday night. Wind speeds over 100 mph were captured at multiple of NWAC’s weather stations around the zone, while others “only” made it to 80 or 90mph. These winds were certainly strong enough to transport any cold and dry snow onto leeward slopes or toward the sides of gullies and bases of cliffs to form dangerous Wind Slabs. The main problem these winds may have had was finding cold dry snow to transport. You’ll have to look to upper elevations above the rain/snow line to find this snow, and subsequently find Wind Slabs. We have some uncertainty around what elevation this transition takes place at, and it may be different depending on where you are in the zone, but it does exist. When you find it, you’ll know immediately and you should be on the lookout for wind-textured snow surfaces, freshly built cornices, and smooth pillow-like piles of snow to help you identify wind-loaded slopes that you should avoid. 

    (1/12/2021) This Storm Slab (D2) naturally triggered on 1/12 at Crystal Mountain. Wind Slabs could act similarly on Thursday on leeward slopes near ridgelines above the rain/snow line.

  • Loose Wet

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

    Looks like we’re going for another wild ride as freezing levels skyrocket to over 10,000 feet in the West South on Thursday. It could feel a bit warmer on the volcanoes where cool winds from the East have less influence than they do on areas closer to the crest. Regardless of your location, if you make it to the upper elevations where cold dry snow exists, and find that the sun is out and snow surfaces are getting wetted for the first time, look out for wet avalanches on terrain features steeper than 35 degrees. Avoid steep rocky slopes and cliff bands, where snow could shed from above. Even tree bombs could trigger these slides. Wet Loose avalanches are capable of entraining lots of snow, triggering slabs, and traveling far distances as they descend. Those fresh cornices that I mentioned a minute ago could also fall if the sun gets to them, so give them a wide berth.

    The snowpack is pretty beat up below the rain/snow line at this point, but may still be capable of producing surprising wet avalanches, such as Glides on Thursday. The snowpack needs time to adjust to all the recent rain and any Glide avalanche would be large to very large. Avoid traveling underneath glide cracks, which look a lot like crevasses.

    (1/1/2021) New rollerballs on the Valley Rd near Paradise, Mt Rainier National Park. Clues like this indicate the surface snow is becoming wet and unstable.

Avalanche Discussion

Well, it could be worse. It could be the 2014-2015 season where we never really had snow to play in. At least we were having a good winter before this event, and I’m sure we will continue that going forward. There’s a lot of winter left. But as of right now, we have transitioned from a cold and snowy playground at all elevations to some sort of wet mess below the rain/snow line throughout the zone in only a few short days. That snowy playground should still exist as you ascend in elevation, but it could be an epic journey to get there. As you might guess, observations have been limited, including automated weather station data, but we are slowly gathering information on what happened around the zone. From the information available, it’s obvious that we just had a major loading event. This event happened relatively quickly, and a widespread natural avalanche cycle occurred as a result of it. There have been large avalanches reported throughout the zone during this cycle, with both wet and dry snow avalanches occurring. In most other zones on the West side of the crest, naturals up to size D3 have been observed. Apart from the in your face avalanche hazard, roads are flooded, power has been knocked out, trees are breaking under the weight of snow and ice, and creeks are running high. If you venture out into the mountains on Thursday, you need to be prepared for things to look very different than just a few days ago. With all this wetted snow and cooling temperatures, the snowpack should be freezing from the top down, potentially creating slide for life conditions. Unless of course the skyrocketing freezing levels and sunshine are able to get to the snow surface and keep things wetted. No matter how the weather shakes out, take it easy out there and realize that there will be other days to make your dreams come true. Since I’m sure you won’t be spending a long day in the mountains, you may as well get home early and share what you found on our public observations page.

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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