Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger increases to High the farther south you travel in the forecast zone. Avoid all avalanche terrain anywhere you encounter very heavy snowfall combined with strong winds, find widespread signs of instability like shooting cracks or whumphing, or see recent avalanche activity. Dangerous avalanche conditions persist in most areas and require a cautious mindset. When in doubt stick to slopes less than 35 degrees. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–3

    West South could see anywhere from a few inches to a few feet of new snow overnight into Wednesday. It will fall on the 12-24” (or more!) of new snow that has come down so far. Winds should also stay strong enough to transport abundant fresh snow onto leeward slopes. Lots of new snow loading up a snowpack with known weak layers is enough to demand extra, extra caution. You are more likely to trigger an avalanche in wind-loaded terrain, but consider all slopes as suspect until proven otherwise.

    Observations were few across the Cascades given stormy conditions pretty much everywhere. With this in mind take an assessment mindset into the mountains with you tomorrow. Start with a conservative plan in simple terrain. Get a handle on weather factors, snowpack structure, and recent avalanche activity before considering anything more complex. The simplest bet will be to stay off large steep slopes or any steep slope with consequences in the runout.

     

    (1/7/2024)

    A large avalanche in the Union Creek drainage near Crystal.

    Photo: Yijie

Avalanche Discussion

Other than stormy, whiteout conditions and lots of closed ski area terrain, the most notable observation came from White Pass where numerous avalanches to D2 were triggered with avalanche control work. The crust-facet combination buried on Jan 2nd is suspected to be the weak layer in these avalanches. Another observer out in the storm easily triggered small, unsupported pockets of wind-drifted snow. 

The snowpack in the West South zone is chock full of potential weak layers. The two that seem to be the most common are the 1/2 and 12/30 crusts. These layers are suspected in a few recent avalanches and could “wake-up” during this major loading event.  They are also the prime suspects in a natural avalanche on Saturday and a human-triggered slide Sunday.

New snow instabilities often gain strength - and avalanche danger falls off - quickly after a storm. Given the presence of weak crust-facet combinations, that may not be the case this time around. Continued avalanche activity since the weekend means these layers are still in play and should be at the top of your list. These slides would be many feet deep, wrap terrain features, and generally ruin your day if you find one. Choose wisely.

On a more positive note . . . . Paradise broke 100" of snow depth as of Tuesday evening. It's about time.

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