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
2 · Modéré
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

As the snow starts to pile up, expect the avalanche danger to rise significantly throughout the day. In areas where you find more than six inches of new snow, start to dial back your slope angle and begin to steer around open areas steeper than 35 degrees. 

Problèmes avalancheux

  • Storm Slabs

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

    We expect heavy snowfall, strong winds, and warm temperatures to all coincide during the day at Snoqualmie Pass. This is a great receipt for storm slab avalanches. First thing in the morning, you likely won’t find enough new snow to pose much of a threat, but as the snow continues to fall and the winds continue to blow that will change. Constantly monitor the new snow. When you measure more than 6” of new snow, find a poor bond to the recent interface, or see blowing snow start dialing back your terrain use. Cracking in the new snow and an upside-down surface should serve as clues to stay off of slopes greater than 35 degrees. You may encounter the largest and easiest to trigger avalanches in terrain where the wind drifts the snow deeper and later in the day. Make sure to consider your route back to the trailhead when creating your plan.

    (2/13/2021) Example: Storm slabs may occur even in small openings or under tree cover once significant snow accumulates. [Photo: Andy Berner]

Avalanche Discussion

You may find the avalanche danger considerably lower than forecasted first thing in the morning, but that will change quickly during the day. Expect the greatest hazard in the afternoon and during periods of the heaviest snowfall. Snoqualmie Pass could receive between 6-10” of snow above 4000’ by the end of the day. This snow will fall on a variety of snow surfaces, which could include firm crusts, weak facets, feathery surface hoar, and settled powder. As a result, you may find that the snow responds very differently from one slope to the next. 

Below treeline, fluctuating temperatures may limit snow accumulation and reduce the storm slab hazard. You could even see rain at Pass level during the day. If you find yourself near the rain-snow line, encounter wet heavy snow, or see new rollerballs, anticipate small loose wet avalanches in nearby steep terrain.

On Tuesday, mostly sunny skies and mild temperatures caused a natural loose wet avalanche cycle at Snoqualmie Pass. These slides occurred on E-S-W aspects and generally remained small. However, several larger and fast-moving avalanches were observed by NWAC forecasters in the field. A few of these point-release slides even triggered shallow slabs as they descended. The recent storms (3/18-3/22) deposited around 2’ of snow at mid-elevations. This snow quickly became wet and heavy on E-S-W aspects Tuesday morning. In more shaded terrain, colder and drier settled snow maintained through the day. This created a very aspect dependent snowpack prior to our next storm.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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