Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Even though the calendar says November, and the sun sits low in the sky, don’t underestimate the combination of direct sunshine and warm temperatures on steep southerly slopes. If you see new rollerballs or find the surface snow becoming wet and sticky, seek out shadier terrain.

Problèmes avalancheux

  • Loose Wet

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

    If the skies stay clear all day, warming temperatures and plenty of sunshine could cause the upper snowpack to become wet, sticky, and unstable. You may notice this first as the surface becomes heavy or natural rollerballs travel downhill in very steep terrain. If you see these signs, it’s time to head for shadier aspects. Recent warming events reached up to around 5500’ in elevation and caused natural loose wet avalanches on Granite Mt. However, the highest elevation peaks around Snoqualmie Pass did not see as significant of warming nor direct sun. As a result, the snowpack in the upper elevations may be most affected by Sunday’s weather. At lower elevations, recent rain and warm weather will likely curtail any significant loose wet issues.

    (11/27/2020) Pinwheels at Mt. Rainier after rising freezing levels and the sun came out a few days after a storm. [S aspect 5400']

Avalanche Discussion

You may find it a bit chilly at the trailheads Sunday morning and wonder if the warming pattern discussed in the forecast was a mistake. Strong temperature inversions could keep the Pass and valley bottoms cold, but expect temperatures to warm significantly as you climb. The biggest source of uncertainty in the forecast comes from the sky. We expect clouds to stay further west throughout the day, but if they show up early, it could limit the sun’s effect and minimize the avalanche danger. 

Even though Saturday’s weather system didn’t produce much precipitation for the Pass, it’s worth remembering that several people triggered and observed slab avalanches Wednesday through Friday. These slides failed on a mid-storm layer about 2” above a thin rain crust from the 24th. At this point, we’re about 4-5 days past the initial loading event, and that layer likely gained strength. However, if you use the nice weather and lower danger Sunday to travel up onto some of the taller peaks in the zone, keep your eyes open on steep shaded slopes, where a pocket of wind drifted snow may linger. 

Early season conditions still exist, particularly near the valley bottoms. Open creeks, small trees, and holes near rocks abound. The snowpack increases in depth dramatically as you ascend and coverage above 4000’ is much deeper than at trailhead levels.

Régions couvertes