Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

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

Points saillants

Buried weak snow could result in high-consequence avalanches on large open slopes. The snowpack may not give you any feedback until the avalanche strikes, so your best bet is avoidance by choosing simple terrain. New snow problems still exist throughout the zone and may present as slabs or loose slides.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2

    This is the problem that should drive your terrain selection. A well-documented weak snowpack exists throughout the zone below all the light and fluffy storm snow. The big question mark revolves around the likelihood of triggering. Can humans trigger this layer a few feet below the surface, or will it take something more sizable, like a cornice collapse or a new storm? The answer isn’t clear, but don’t take the gamble. Avoid large open terrain where triggering one of these slides would have devastating consequences. Instead, stick to small low-angle or treed slopes.

    (2/2/2025)

    This avalanche occurred after an audible whumpf. The slide failed on facets over a crust and released the entire width of the feature. NE, 3700ft

    Photo: Summit at Snoqualmie Professional Patrol

  • Wind Slabs

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

    Above our weak interfaces, there is plenty of recent storm snow. You’ll likely need to manage it on slopes over 35 degrees, and it could look different depending on your terrain. We’re calling it a wind slab since wind-loaded slopes will be the most likely location to trigger an avalanche large enough to call consequential. Look for actively blowing snow, fresh cornices, or large pillow-like drifts to help identify wind-loaded features to avoid. You’ll likely notice that the snow is stiffer in wind-affected terrain than the light and fluffy snow elsewhere. 

    Speaking of the low-density storm snow, in sheltered terrain you may see loose avalanches running in the surface snow. Some could fail during periods of sunshine or due to snow shedding from trees and rocks.

    (2/6/2025)

    A large avalanche on Mount Snoqualmie. The failure layer is unknown. We suspect it failed on 2/5. [N/NE 6100' Crooked Couloir]

    Photo: Eddie Schoen

Avalanche Discussion

On Thursday, NWAC forecasters were on Kendall Peak looking at the January Drought Crust (JDL) and the 1/10 complex. They continued to get propagation saw tests to fail to the end of the column with relatively short cut lengths (~35/100). They also noted a few natural avalanches in steep rocky terrain - both loose and shallow slabs. Avalanche professionals on Cave Ridge and near Pineapple Pass had very similar reports.

An avalanche professional observed a large natural avalanche on Mount Snoqualmie. The failure date is unknown, but we suspect it failed on 2/5. It looks similar to a large wind slab, but we can’t rule out that persistent grains were involved, especially given its aspect and elevation (N/NE ~6100’). The Summit at Snoqualmie Pro Patrol reported an audible whumpf and resulting avalanche down to the 1/10 complex that occurred on 2/5 in west-facing terrain.

Although the JDL and 1/10 complex present differently across the landscape, they are generally considered weak. Test results continue to suggest that these layers can propagate a fracture given the right trigger. The storm snow above them is mostly right-side-up but contains some weak points that could fail in specific terrain. Relatively benign weather could help some of these typical storm layers start to heal, but it won’t be enough to cure those persistent problems. There's plenty of snow available for transport, and wind-loading was observed on Thursday, along with some solar-induced slides. It remains to be seen if sunshine helps the storm snow “slab up,” inching us closer to more avalanche activity on our buried weak layers. 

Régions couvertes