Bulletin d’avalanche

East Slopes South

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Strong winds and new snow will develop dangerous avalanche conditions at upper elevations. You could easily trigger large avalanches in wind drifted snow. Avoid steep open slopes with stiff wind-drifted snow and seek out lower angle or sheltered terrain instead.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2

    Strong winds and a significant storm will impact the Cascades on Wednesday. Expect peak precipitation to occur during the day, with increasing wind speeds. Plenty of snow is available for transport, and the storm will bring plenty more snow over the Cascade crest to the east slopes of the Cascades. Winds are forecasted in the 25-35mph range and will easily drift snow around, even at lower elevations. So any steep open terrain will potentially harbor large wind slabs. But avoiding these wind slabs in alpine terrain will be especially challenging. So while the storm pummels the mountains, avoiding steep, wind-exposed terrain at all elevations will be best. Simple, low-angle slopes will be the best option to reduce to likelihood of triggering an avalanche. The most likely places to trigger wind slabs will be steep slopes below ridges, steep convex rolls, and the base of cliffs. Feel for stiff over soft snow layering and look for signs of cracking or collapsing to identify and avoid areas of unstable wind-drifted snow. New snow will accumulate on various surfaces, including slick crusts on southerly slopes and weak snow on northerly aspects. Therefore you could find reactive storm slabs on steep slopes in sheltered areas. You can use small, inconsequential test slopes and quick hand pits to observe how the new snow reacts. Avoid steep terrain if you find the new snow sliding easily or test slopes producing mini avalanches.

    (2/28/2023)

    These pillow like drifts below ridges are prime locations to trigger a wind slab. 

    Photo: Katie Warren

Avalanche Discussion

A generally strong snowpack exists throughout the East South, and the recent storms have been improving winter recreation opportunities significantly. However, the recent snow has piled up on various crusts. While we have not seen any avalanche activity on deeper, older snow layers, we are tracking these interfaces with the additional loading events. 

I traveled into the Ahtanum Meadows area on Tuesday. Generally, I found 7-12 inches of new snow and excellent riding conditions. Snowpack test yielded unremarkable results. However, I did observe some weak snow below the Valentine's Crust, about 20 inches below the snow surface. You can check out my observation here for more details. Before the storm cycle on the 25th, Joe Dellaporta traveled into the American Ridge area near Bumping Lake and observed slick surfaces at lower elevations, dry faceting snow at upper elevations in the shade, and a thin sun crust on slopes with a southern tilt (observation). 

Thanks for the recent observations!

Régions couvertes