Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

After the recent snowfall and winds, you could still trigger avalanches in pockets of wind drifted snow. Terrain features of concern are ridges, the base of cliffs, and steep rollovers midslope, particularly in alpine terrain. Look for these smooth, pillow like drifts and steer around these features where you find them in steep terrain.

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    As the morning progresses, clouds may thin, and the sun is likely to make an appearance in the afternoon. The fresh snow will be particularly sensitive to sun and warming. So a healthy dose of sunshine along with warming temperatures will likely lead to wet loose avalanches in steep, sunny slopes. Cliffs, rocks, and tree bombs are often where these avalanches initiate from, so be aware of overhead hazard from steep, sunny terrain. If you feel the snow beneath you becoming sticky with wet surfaces in the sun, move to lower angle or shadier terrain. 

  • Wind Slabs

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

    Strong winds drifted around Saturday's storm snow, and shallow wind slabs were a common problem on Sunday. There will still be lingering pockets of unstable wind slabs where you could trigger an avalanche on Monday. Most of these should be small and possibly stubborn to trigger. However, as you ascend in elevation, avalanches are likely to be larger and remain more sensitive. Look for smooth pillow-like drifts, textured surfaces, and cornices along ridgelines to identify probable wind slab locations. Before committing to steep slopes in wind exposed areas, look for signs of instability in small test slopes, such as long shooting cracks. Steer around these stiff drifts of snow where they exist on slopes greater than 35 degrees. 

    (1/20/2023) A small skier triggered wind pocket on a convexity. Note the slightly textured surface. Photo: Andy Harrington

Avalanche Discussion

Saturday night into Sunday brought 7-10 inches of new snow with gusty winds to Snoqualmie Pass. Observations from Sunday indicated shallow wind slabs as the primary concern. But the new snow is stacking up on various surfaces and burying the MLK crust deeper. Before this storm, slopes in the direct sun had a thin sun crust, while shadier terrain preserved some weaker surfaces. Before stepping out into more committing or steep terrain on Monday, take a minute to check the bonding of the new snow to the old surface to see if it fails easily wherever you're recreating. Slopes with a weak interface between the old and new snow layer could break wider than anticipated. On slopes with a sun crust, a bed surface may now exist for avalanches to run far and fast, whether that's in loose form or as a slab. Any avalanche should only include the snow above the MLK crust (about 1.5-2 feet below the surface), and the majority should revolve around the new storm snow.

Régions couvertes