Bulletin d’avalanche

East Slopes South

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 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Winds may drift the snow into stiff slabs where you could trigger an avalanche. Upper elevations below corniced ridgelines or the base of cliffs are the most likely spots for these avalanches. There is also potential for avalanches on deeply buried weak layers. These avalanches are less likely, but consider the much higher consequences of one of these much larger avalanches if you venture into shady slopes at high elevations. 

Problèmes avalancheux

  • Wind Slabs

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

    At upper elevations, winds may drift the recent snow into stiffer slabs where you could trigger an avalanche. Slopes below ridgelines and the base of cliffs are likely spots for wind slabs to form. Look for textured surfaces or stiff, hollow-sounding snow to identify wind slab locations. If you see shooting cracks in wind-stiffened snow, this is a sign to choose low-angle terrain. Cornice falls are common this time of year and are a hazard on their own, but they can also trigger slab avalanches on the slopes below. Don't linger for long beneath these monsters. We expect most of these avalanches to be small, but there is potential for these avalanches to step down into deeper layers and become large. 

    (3/18/2022)

    An example of a small wind slab below a corniced ridge.

    Photo: Andrew Kiefer

  • Persistent Slabs

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

    Despite the recent warm temperatures, things didn't quite get hot enough for long enough on the northern aspects to help destroy the weak snowpack structure. Weak, faceted snow over the Early February Crust (EFC) still exists, buried 2-4 feet deep on NE to NW aspects at mid and upper elevations. Triggering one of these unsurvivable avalanches is still possible, particularly in wind-loaded alpine terrain with large open bowls. The recent snow load may be enough to make triggering a large and surprising avalanche more likely for a few days. 

    These avalanches can be surprising, propagating widely or getting triggered from a distance. You may or may not see any signs of instability before triggering this type of avalanche. The best way to reduce your risk of triggering one is by avoiding steep, rocky, wind-swept terrain on the north side of the compass. 

    (3/6/2024)

    Steep, shady, wind-loaded terrain is the type of terrain that the persistent problem could plague. 

    Photo: Anthony Lubetski

Avalanche Discussion

If you enjoyed the sunshine on Sunday, be prepared for a cloudier day on Monday with the chance of a few light rain and snow showers. 

While it may not be a sunny day, warm temperatures mean you may trigger some small wet loose avalanches as the snowpack warms in the afternoon. It is early spring, and the dynamic spring weather brings dynamic avalanche conditions. New snow concerns like wind and storm slabs can quickly become wet snow problems by the afternoon. Make frequent observations, and be prepared for rapidly changing conditions and snow stability. 

This past system favored the east slopes of the Cascades. Weather stations across the zone picked up around 6-12 inches of new snow above about 5000ft, with rain below. Observers in neighboring zones reported wet snow easily shedding and even small storm slabs releasing. 

I was in the Ahtanum/Darland Mt area last Tuesday. The prolonged period of sun and warm temperatures had done a number on the lower elevation snowpack and steeper southerly slopes. The snowpack on southerly aspects was wet and moist to the ground but more supportable than other sunny aspects where you could punch through wet snow to your waist. Northerly aspects held a colder, more layered snowpack, with preserved weak snow over the early February crust about 4' down on a N aspect @ 6700'. 

Observations have been sparse. Help create a more accurate forecast by submitting your public observations here. 

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