Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A sizeable storm in the forecast means you can trigger slab avalanches in layers of new and wind-drifted snow on Sunday.  Stick to sheltered, lower-angled terrain and limit exposure to big slopes overhead during periods of heavy snowfall.  Strong winds, snowfall, and poor visibility could make navigating bigger, more open terrain difficult.  Plan on starting and probably finishing your day with a conservative plan.

Avalanche problems

  • Storm Slabs

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

    It won’t be the day to tip-toe around the avalanche problem. In addition to the increasing likelihood of human and naturally triggered avalanches, weather conditions should make navigating and assessing avalanche terrain quite difficult. Expect moderate snowfall and strong winds to persist for much of the day.

    You are more likely to trigger an avalanche on wind-loaded slopes. But consider all steep slopes as suspect given the amount of new snow in the forecast and the possibility it’s loading layers of buried surface hoar and weak facets. Don't ignore signs of instability like whumphing or shooting cracks. When in doubt, stay on slopes to low in angle to slide

    (1/18/2024)

    Small avalanches on features like this gully wall are a good sign you can trigger a larger avalanche on a bigger slope.

    Photo: Irene Henninger

Avalanche Discussion

If snow levels are slightly higher than forecast, you could see rollerballs and small wet avalanches at lower and even mid-elevations.  Natural wet loose avalanches tend to initiate in cliffy or treed terrain. You can also get wet snow moving downhill with you when descending steep slopes. Lower elevations may not be significantly safer if it’s raining or the snow is wet and mushy.

Besides fresh slabs of new and wind-drifted snow, the main factor affecting stability going into the weekend is how much surface hoar survived the first round of wind and increasing temperatures. A layer of surface hoar buried about a foot deep was found in wind-sheltered, northerly terrain in a neighboring forecast zone. It repeatedly produced propagation in testing. While this is only one observation, it also confirms that buried surface hoar can be found in terrain with certain characteristics - mid-elevation, shaded slopes where the surface hoar didn’t melt and the wind didn’t blow it away.

On Saturday, observers in West North reported marginal visibility, strong winds, and fresh, reactive wind slabs on leeward aspects. While none of the reported wind slabs were bigger than D1, difficult travel likely kept most people out of the kind of terrain where they could trigger anything bigger. A thin but crunchy rain crust was found on all aspects up to and above 4500’.  Lighter winds and notably less wind transport were observed in Stevens and Snoqualmie Passes. The only recently reported avalanche from either of these zones was a small but remotely triggered wind slab avalanche in Snoqualmie Pass. on Friday.

 

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