Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Saturday should be a transition day as we move toward colder weather. Keep low-likelihood, high-consequence wet slides in the back of your mind until a thick surface crust develops. You may find that travel conditions pose a greater hazard than avalanches throughout much of the zone.

Problèmes avalancheux

  • Glide Cracks

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–2.5

    We'll finally start cooling down on Saturday, which should put an end to our wet avalanche concerns. Although lower-elevation snow is capped by a stiff freezing rain crust, wet and punchy snow likely still exists higher up. We've gone several nights without a strong overnight freeze, and rain showers have fizzled in and out the past few days.  Wet snow avalanches are hard to predict, but the tea leaves indicate that they could still occur at Snoqualmie, particularly in the morning hours. We're talking about low-likelihood, high-consequence wet slides such as glides. Look for slopes with sagging cornices, crevasse-like cracks, or blocks of snow clinging to rocky ledges. They can help you identify locations where one of these unpredictable avalanches could occur. 

    (12/18/2024)

    A large pile of wet avalanche debris from natural glide avalanches at Alpental this week.

    Photo: Summit at Snoqualmie Pro Patrol

Avalanche Discussion

The winds of change are blowing, and that's a good thing for Snoqualmie Pass. The past week has been warm and wet, with an atmospheric river (AR) delivering roughly 3.5" of precipitation on Tuesday evening. The AR started as snow, but quickly transitioned to rain above ~4400' and freezing rain below. This made a mess of our already thin early-season snowpack and kicked off a wet avalanche cycle. 

Travel has been difficult at The Pass since the storm. A stout freezing rain crust at lower elevations helped save our snowpack, but also became a barrier to access the mountains. Pro patrollers from The Summit at Snoqualmie have been out and about this week, letting us know about glide avalanches in the Alpental Valley. We've kept this problem in the forecast for several days now as the warm and at times, wet, weather continued. 

On Saturday, we're forecast to start the day warm before a pattern shift slowly lowers freezing levels during the onset of precipitation. Expect to experience significant winds throughout the day. The combination of strong winds and lowering freezing levels should be enough to fully lock up the surface of the snowpack and put an end to our wet avalanche concerns. Of course, if the temps drop fast enough and newly fallen snow starts to blow around in the strong winds, you could find a few pockets of wind-drifted snow by day's end. 

This week certainly didn't help build our early-season snowpack or alleviate our travel concerns. Anticipate difficult travel due to hazards such as firm crusts, frozen avalanche debris, swollen creeks, open holes, and exposed rocks/logs. In certain terrain, there’s a chance you could slip and go for a long uncontrolled slide. So travel with the appropriate gear and default to lower-angled slopes if the surface is firm and slick.

Régions couvertes