Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Continued sunny weather and high freezing levels will maintain our concern for avalanches on Friday. It could take some time for the sun to overcome cool morning temperatures and increase the hazard. 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

    Keep an eye out for rollerballs and pinwheels or the snow surface getting warm and sticky as indicators that the sun is destabilizing the snow surface on Friday. If you notice these signs, natural Wet Loose avalanches may follow or you may be capable of pushing snow downhill to create Wet Loose avalanches of your own. These avalanches will be more likely on slopes that see direct sunshine, particularly later in the day as the snow surface softens, 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.

    (3/9/2021) Rollerballs and pinwheels were already observed within the zone the past few days with filtered sunshine. On Thursday, we expect to see more of these and some actual Wet Loose avalanches due to more sunshine and rising freezing levels. [Photo: Enji Cooper]

Avalanche Discussion

Freezing levels on Friday are expected to continue to rise as high pressure and mostly sunny skies maintain their hold on the Snoqualmie Pass zone. Small Wet Loose avalanches and rollerballs have recently been observed at the pass during this warm-up, and we expect this to continue as we move toward the weekend. These avalanches have needed some time to overcome the cool morning temperatures, meaning that hazard is typically increasing throughout the day as the sun’s influence grows stronger. In addition to Wet Loose avalanches, cornice falls and glide slopes are other avalanche hazards often associated with a warm-up and you should continue to give these hazards a wide berth as we transition toward a more spring-like snowpack. On aspects that do not see direct sunshine, you could find that cold dry snow still exists over the 3/5 crust. Signs point toward a weakening bond with the 3/5 crust, so keep dry loose avalanches or pockets of wind-drifted snow on your radar on these slopes and don’t get swept off your feet in consequential terrain.

We have decided to remove the Deep Persistent Slab problem from our official problem list at Snoqualmie Pass. 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 at Snoqualmie Pass was over a week ago. (The Chair Peak slide on 2/28-3/1). The last suspected avalanche on this layer throughout the region may have been a few days later in the West South.
  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 8-10 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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