Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You'll likely notice the wind if you’re out exploring your relationship with the mountains on Wednesday. If you see snow blowing into new drifts, consider the potential for wind slabs. Due to the atypical wind direction, they may be in locations you’re not used to.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    We’re in store for an east wind event at Snoqualmie Pass. After a warm couple of days, the question becomes - how much snow is available for transport? There’s likely just enough dry snow out there that you’ll need to look out for fresh slabs on specific terrain features such as rocky chutes or convexities. Easterly winds often result in more cross-loading and mid-slope loading than you might be used to. They also load different aspects than our typical storms. Look for actively blowing snow or new drifts to identify wind-loaded features to avoid. You can use small test slopes to check the reactivity of potential slabs.

    On Tuesday, NWAC forecasters and avalanche professionals both observed wind slabs near rocky terrain. There could be a few older slabs out there in similar areas on Wednesday interspersed with the newly built ones. 

    (2/13/2024)

    A small skier-triggered wind slab in a confined/rocky chute. It failed on the Early February Crust. 

    Photo: Andy Harrington

Avalanche Discussion

After a few days of warm weather resulting in widespread wet avalanche activity, we’re turning the page and heading back into a colder regime. Easterly winds are expected to ramp up on Wednesday ahead of an approaching storm system. 

The focus now turns to the snow surface. How much snow is available for transport on Wednesday, and what will new snow be falling on? There’s a mixed bag out there, depending on your aspect or elevation. 

At mid to upper elevations, you can generally find 1-1.5 feet of snow over the stout Early February Crust (EFC). The moisture content and amount of crusts within this snow varies greatly between shaded and sun-exposed slopes. You’ll find crust sandwiches or a thicker EFC on slopes that typically see direct sunshine. The possibility of weak facets is higher on shaded slopes, including right on top of the EFC. Most aspects have seen at least some warming over the past few days, softening the surface.

A new crust is expected to form as the moist surface cools on Wednesday night. Surface hoar was widespread on Tuesday and could persist in wind and sun-sheltered locations. We expect all avalanche activity in the coming days to be confined to the snow above the EFC, with most occurring within the incoming snow.

Lower elevations contain few avalanche problems, but travel can be difficult. You’ll likely need to navigate slick crusts, open creeks, exposed rocks, and refrozen avalanche debris.

Régions couvertes