Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 8 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Snow will continue to stack up through Wednesday, with avalanche activity likely across all elevations. Unstable slopes could exist anywhere the new or wind drifted snow has accumulated. Stick to terrain below 35 degrees, and limit your time traveling under steep, unsupported slopes. 

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Snowfall will continue on Wednesday, increasing the likelihood of storm slab avalanches. Expect avalanche activity anywhere new snow has accumulated, which will include all elevation bands. A brief warm-up Tuesday night may create an “upside-down” snow structure, with denser snow overlying lighter snow, increasing the reactivity of storm slabs. With continued snowfall and wind transport, don't rule out the chance of a natural release at upper elevations.

    With all this wind, large wind slabs are likely growing near ridgelines, rock outcroppings, and even between treed areas. Extra caution is warranted on leeward slopes, where slabs may be thicker and capable of breaking deeper with the combined wind-transported snow.

    Thoughtful terrain selection will be critical for safe travel on Wednesday. Signs of instability such as shooting cracks, failing test slopes, or recent natural avalanches are clear indicators of an unstable snowpack. If in doubt, choose simple terrain, stick to lower-angle slopes, and minimize exposure to steep terrain above you.

    (1/7/2025)

    Natural avalanches on the south side of Red Mt from last season. SS-N-D2/R2-U.

    Photo: Dallas Glass

Avalanche Discussion

It has been a proper storm day in Snoqualmie Pass. Since early this morning, 6" of new snow has accumulated at Pass level, while upper elevations in Alpental have picked up closer to 9". These totals are likely to increase significantly over the next 24 hours as the storm continues. Winds have been moderate to strong at upper elevations, with lighter winds observed at mid and lower elevations. Summit at Snoqualmie–Alpental Pro Patrol reported several natural slab avalanches near ridgelines, failing 6-7" deep.

Forecasters traveled into the Alpental Valley on Tuesday, visiting both the Source Lake area and the Mount Snoqualmie–Snow Lake Divide. Both locations showed wintery conditions, with poor visibility and continuous, intensifying snowfall throughout the morning. Snow depths ranged from approximately 1.5 to 4 feet, with a few inches of new snow accumulating before midday. By midafternoon, warming temperatures allowed for denser snow to fall on lighter snow from earlier in the day.

The January 3rd crust continues to show variability in thickness and supportability across the zone. At mid and upper elevations, the crust is generally thinner, more friable, and at times difficult to identify. In contrast, lower elevations hold a thicker, more supportable crust. In areas with thinner overall snow cover, the crust has been able to harden and become more supportive. To date, no significant avalanche activity has been observed failing on the January 3rd crust.

Régions couvertes