Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
2 · Modéré
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

Changes in precipitation type will result in a change in avalanche potential. Your primary avalanche problem will depend on where you are in the zone or what elevation band you’re traveling in. Make travel plans that allow you a quick exit back to your car if the weather isn’t panning out how you hoped.

Problèmes avalancheux

  • Loose Wet

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

    The highest chance for wet avalanches will be in locations where rain falls on dry snow for the first time. Areas such as the Pass proper or the eastern part of the zone that have remained cold recently come to mind as examples of where wet avalanches may be more prevalent. These slides often start at a point and fan out as they descend, possibly growing large or triggering slabs in the process. Avoid steep slopes over 35 degrees if you see new rollerballs and pinwheels, fan-shaped avalanche debris, or rain falling on dry snow.

    (1/20/2024)

    Rollerballs and snow shedding from trees and rocks are indicators of wet avalanche potential. 

    Photo: Nicco Muratore

  • Wind Slabs

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

    Above the rain/snow line, fresh wind slabs might develop on leeward slopes or near the base of cliffs. Look for actively blowing snow and new drifts to help identify wind-loaded features. Use small test slopes and uptrack tests to look for cracking of the surface or snow failing in blocks to help indicate instability. Of course, seeing other avalanches is the surest bet that the snowpack is unstable and a good indication that you should dial back your terrain choices. Otherwise, steer around wind-loaded features where you’re more likely to trigger an avalanche.

    (1/20/2024)

    A shallow wind slab at the base of rocky terrain. 

    Photo: Dallas Glass

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–3

    The transition to warmer temperatures and the addition of liquid precipitation will help to stress our snowpack and our deeper layers of concern. It’s been over a week since our last suspected avalanche on the Solstice Crust complex. In neighboring zones, this layer has been much more active. Although unlikely, an avalanche on this layer would be very large and destructive. You won’t get any warning or notice signs of instability before they fail. Your best mitigation tool will be to minimize your exposure to big open slopes.

    (1/10/2024)

    This very large avalanche released using explosives during avalanche control at Alpental. It is an indication that deeply buried weak layers could still be active. 

    Photo: Alpental Ski Patrol

Avalanche Discussion

It’s shaping up to be a messy Sunday in the Snoqualmie Pass zone. You could encounter snow, rain, freezing rain, or sleet during your travels. You will probably experience some combination of them if you’re out long enough and cover enough distance. This is not a favorable flow pattern for the Pass, which could be good or bad, depending on your outlook on life.

We’re transitioning from a cold and dry snowpack into something warmer and wetter. Areas not heavily influenced by the east flow have already felt this change with more widespread wet avalanche activity such as rollerballs and pinwheels. On Saturday, avalanche professionals and recreationalists reported variable conditions, including freezing rain crusts, well-settled powder, and moist surface snow. Small wind slabs and wet avalanches were spotted. In the eastern part of the zone, conditions are colder and more winterlike. 

Unusual weather can result in unusual avalanches. The freezing rain crusts reported on Saturday could make a good sliding surface for new snow on Sunday. The 1/16 interface has spotty distribution but contains faceted grains. It may have been the failure point for an avalanche on Dungeon Peak on Friday. One avalanche professional observed a whumpfing collapse at lower elevations in Commonwealth Basin on Saturday, which may have been the 1/16. Small avalanches could step down and trigger deeper pockets on this layer in isolated locations on Sunday.

Régions couvertes