Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Direct sunshine and rising freezing levels could help destabilize the snow surface and produce some Wet Loose avalanches on Thursday. If you notice recent avalanches with fan-shaped debris or fresh rollerballs, head for shadier slopes.

Avalanche problems

  • Loose Wet

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

    Bright sunshine and rising freezing levels are forecasted for Thursday around the West South zone. In many areas, this will be the first day of full sunshine since recent snow has fallen, putting Wet Loose avalanches on our radar. You can look for rollerballs and pinwheels or the snow surface getting warm and sticky as indicators that the sun is destabilizing the snow surface and Wet Loose avalanches may follow. These avalanches will be more likely on slopes that see direct sunshine and could be larger as you ascend in elevation. These slides often start at a point and can entrain snow, fan-out, and even trigger slabs as they descend downhill. You can minimize your exposure to these avalanches by heading toward shadier slopes and ensuring that the slopes above you are not in the sunshine.

    (2/28/2021) Pinwheels and rollerballs were observed the last time the zone went through a warm-up about a week ago. These are good indicators of Wet Loose avalanche potential. [Photo: Enji Cooper]

Avalanche Discussion

You may have already seen some rollerballing or small Wet Loose activity over the past few days due to filtered sunshine and fluctuating freezing levels around the West South. Thursday should be a notch up over the past few days and we expect more widespread avalanche activity involving the recent storm snow sitting atop the 3/5 crust. Whenever we talk about a warm-up and direct sunshine this time of year, you should also keep cornices on your mind. Continue to give cornices a wide berth by not traveling too close to them on ridgelines and staying out from under them. The same can be said for icefall or glide slopes if you find yourself in a location where these hazards exist. On slopes that do not see direct sunshine on Thursday, you could still find some cold dry snow and some isolated lingering Wind Slabs to steer around. These wind-loaded features may be more prevalent as you ascend in elevation and could exist on some uncommon terrain features due to a switch in wind direction over the past weekend.  

We have decided to remove the Deep Persistent Slab problem from our official problem list in the West South. Although the weak snowpack structure remains, a few data points have made us feel more comfortable with this layer than we have recently.

  1. Our last confirmed natural avalanche on the Mid-January crust/facet layer in the West South was over a week ago. (Weekend of 2/27-2/28 near Crystal Mountain).
  2. We have a generally strong and well-settled upper snowpack above this layer. This includes the most recent 3/5 crust, which is thick and supportable in most locations throughout the zone.
  3. Since our last major loading event on this layer, test results have become more inconsistent than they were previously. 

The Mid-January crust still remains 6-10+ feet deep in the snowpack throughout much of the zone, and we believe it is currently dormant. It may wake back up at some point this season, however. At that point, we will put it back on the official problem list and continue to talk about the dangers this layer presents. Until that time, don’t forget about this layer. If you choose to enter more complex or large avalanche terrain, you should continue to talk with your partners about the low-likelihood/high consequence avalanches this layer is capable of producing. Keep in mind that when they occur, these avalanches have broken trees and descended far distances toward their maximum runouts in valley bottoms. The best way to mitigate your risk is to limit your time in and below large avalanche start zones, paths, and runouts. 

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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