Avalanche forecast

West Slopes South

Northwest Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

As we transition out of a major storm cycle into nicer weather, human triggered avalanches will continue to be of concern on Wednesday. Avoid wind-drifted piles of snow where avalanches could be triggered more easily. If you feel the snow getting wet and sticky from the sun, head for shadier slopes. 

Avalanche problems

  • Wind Slabs

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

    Strong winds have been creating Wind Slabs throughout the West South in areas that have received snow instead of rain. Wind Slabs are often found on leeward slopes, at the base of cliffs, or on the sides of gullies, but take note of fresh cornices, textured surfaces, or smooth pillow-like piles of snow to help you determine more specific locations to avoid. As you ascend in elevation above the previous rain line from this weekend, slabs could be much larger and possibly more reactive. They could also be harder and feel hollow beneath your feet. As you travel, take note of clues of unstable snow such as shooting cracks or whumpfing collapses, and use small test slopes to test for slab potential and poor reactivity. If you notice any of these signs of instability, steer around wind-loaded slopes.

    (12/22/2020) This Wind Slab was human triggered on Tuesday on a common ascent route in the neighboring Snoqualmie Pass zone.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Rising freezing levels throughout the day and some sunshine could combine to trigger a few Wet Loose avalanches on Wednesday on solar slopes. Closer to the crest, some cool East winds could keep the Wet Loose at bay. Areas further from the crest or protected from the East winds, such as on the volcanoes, should be a bit warmer and the snow surface could destabilize to create avalanches. In short, if you feel the snow surface heating up, you should be aware that Wet Loose avalanches are possible and of your exposure to avalanche terrain. If you notice rollerballs, snow shedding from rocks, or see fan-shaped avalanche debris, seek out shaded terrain away from sun-exposed slopes above you.

Avalanche Discussion

It was nice to wake up to some snow on Tuesday morning after a weekend that saw areas of the West South get close to 5” of rain. Most NWAC weather stations recorded between 4-7” of new snow that was accompanied by some gusty winds. This snow is helping us to change our focus toward new snow avalanche problems and away from the wet and wild weekend which saw widespread Wet Slab avalanche activity throughout the zone. Although no longer our main focus, this past weekend is not something to be put out of your mind completely. We just received a pretty ridiculous amount of water in a fairly short time period, and as mentioned above, saw a lot of avalanches, so it’s worth revisiting quickly. We have been concerned about weak snow (12/13) sitting a few inches above a prominent crust (12/9) throughout the zone. Prior to Saturday night, this weak snow was buried as deep as 3 feet. Sunday morning brought word from Crystal Mountain Pro Patrol of multiple crowns in the Crystal Mountain backcountry, with slides estimated up to size D2. Sunday and Monday, NWAC observers and forecasters were able to confirm a widespread avalanche cycle at Paradise with over 20 avalanches counted within a relatively small geographic area and with poor visibility. The largest slide appeared to approach size D3 and had close to a 3-foot crown. On Tuesday, White Pass Pro Patrol was able to get visibility into the surrounding mountains and confirmed that there were multiple large avalanches that had occurred in the Goat Rocks Wilderness. What this tells me is that the snowpack had a weak structure and we certainly put enough load on it to test that structure, with the result being lots of avalanches large enough to bury or kill you. Does this mean that this layer is now played out and we can take it off our radar? I wouldn’t go that far quite yet, but avalanches appear to be trending toward unlikely.

As we move through the holiday week and into some nicer weather, we anticipate a busy few days in the backcountry. Before heading into consequential terrain, think about what we do and do not know about the snowpack structure and this previous storm. Take some time and do a little digging where you are looking to recreate to determine if the 12/13 layer is still present or if there are any interstorm layers that are reactive to your weight. The likelihood for natural avalanches is decreasing, but conditions could still be ripe for human triggered avalanches to occur, particularly if you find yourself in terrain that did not slide during the previous cycle or has been recently affected by the wind. When in doubt, dial back your terrain choices.

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.

Regions covered