Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

You will find dangerous avalanche conditions and overlapping new snow problems in the mountains of the West South on Wednesday. Give the snowpack time to adjust to the recent stormy weather by avoiding slopes over 35 degrees where you’re more likely to trigger an avalanche.

Avalanche problems

  • Storm Slabs

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

    The storm isn’t quite over yet. We should still squeeze out a few more inches of snow before skies start to clear on Wednesday. Slabs will be larger, and possibly more reactive, as you ascend in elevation or in wind-loaded terrain. Take the time to investigate all of the recent snow above the 2/3 interface for storm instabilities, a poor bond, or heavy over weak snow. You should dig with your shovel or hand to look for these potential points of failure. Visual clues such as recent avalanches, shooting cracks, or whumpfing collapses as you travel are bullseye information that the snowpack needs more time to heal. You can also use small test slopes to see how the storm snow is failing under your weight. If you notice it is failing in blocks or see any of the signs of instability listed above, avoid slopes over 35 degrees.

    Reports from Tuesday indicate there was plenty of wind transport of the newly fallen snow as well. The management of Wind Slabs is not much different in this case than that of the Storm Slabs. You should avoid slopes over 35 degrees if you suspect them to be wind-loaded. Be cautious on the leeward side of ridgelines or anywhere you notice smooth pillow-like piles of snow.

    (2/7/2023)

    A skier intentionally triggered a slab on a test slope near White Pass on 2/7. This crown is about 1 foot deep. [W 6400']

    Photo: Dallas Glass

  • Loose Wet

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

    In addition to the larger and more dangerous slabs, there are other new snow issues you might encounter on Wednesday. The sun is forecasted to make an appearance in the afternoon and could destabilize the snow surface resulting in Wet Loose avalanches. This may not pan out, but if the conditions are met these avalanches could grow large and are worth putting on your radar. Look for snow shedding from trees and rocks or fresh rollerballs/pinwheels on sun-exposed slopes. These are precursors to Wet Loose avalanches and should be a sign for you to head for shadier slopes. These slides often start at a point and then fan out as they descend, possibly growing large or even triggering slabs. On some slopes, this same process could manifest as solar-induced Dry Loose. Their activity, signs, and management are the same. If you suspect that a loose cycle is imminent, head for shadier slopes away from overhead hazard. 

    (1/1/2023)

    If the sun comes out on Wednesday, you could see natural rollerballs and loose wet avalanches on steep sun-exposed slopes.

    Photo: Dallas Glass

Avalanche Discussion

As of Tuesday afternoon, the West South is still in the midst of a storm delivering steady snow showers and wind. We should see continued snowfall accompanied by cooling temperatures into the overnight hours before precipitation starts to taper. 

Observations to this point are limited, but avalanche professionals near White Pass reported triggering slabs as deep as 1 foot on test slopes and plenty of wind transport. That likely extended north along the crest to the Crystal Mountain area where Pro Patrol reported that cornices were building throughout the day. Recreationalists in the Crystal Mountain backcountry corroborated this report mentioning significant wind transport on East Peak. As expected, Paradise far outpaced other areas of the zone and has recorded over a foot of new snow. 

This storm comes on the heels of a weekend where multiple shallow avalanches were triggered throughout the zone. These slides are suspected to have failed at the 2/3 interface or just above it. As skies clear on Wednesday and peak storm instability passes, slopes should again be primed for human-triggered avalanches. If the same weakness that resulted in avalanches over the weekend remains, slides could be large and more consequential moving forward. You should focus your observations on the snow above the 2/3 interface before committing to terrain. Although we do have some layers of concern below this layer and above the MLK crust, we have not received word of any avalanches breaking down to these layers as of Tuesday evening. 

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