Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You can trigger avalanches where you find shallow drifts of new snow at upper elevations. You may find areas of weak, older snow in cold, shaded valleys. Expect light snow with clearing skies in the afternoon.

Problèmes avalancheux

  • Wind Slabs

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

    Watch for triggering small slab avalanches in freshly drifted snow on leeward sides of ridges at upper elevations. Steer around drifts and wind-loaded slopes steeper than 35 degrees. You can use a pole to feel for stiffer, wind-transported snow and deeper drifts.  At upper elevations, you may find 4-6" of recent snow and drifted slabs up to 1 foot deep. The initial slabs formed late on Wednesday and may continue to form into Friday. On Thursday, an observer reported a small wind slab avalanche in Spire Gulley, pictured here.

    (12/7/2023)

    A shallow crown (20cm) from a small triggered wind slab avalanche in Spire Gulley. NE, 7,300ft

Avalanche Discussion

After light snow early in the day, skies may clear on Friday afternoon. I don't anticipate enough sun to cause avalanches.

If you experience whumping collapses, stick to lower-angle slopes and avoid large terrain features. While avalanches on old, weak layers are unlikely, it's worth keeping a decent buffer around large terrain until the wet snow in the upper snowpack can freeze into a more stout crust. The November 30th surface hoar may still be intact in cold valley bottoms east of Washington Pass. Even in these areas, you can find the weak layer in the middle of the snowpack, capped with a surface layer of top 6-10" of rain-soaked snow. The progressively freezing melt forms are slowly adding strength to the snowpack. I suspect that even where the surface hoar is found, it likely is no longer a culprit weak layer for avalanches.

On Thursday, Willie Webster surveyed the snowpack throughout the Highway 20 corridor. He found the above-mentioned weak structure in the Hairpin Valley. The entire snowpack at the aptly named Rainy Pass had been wetted all the way to the ground. Any weak layers that had existed there are likely no longer an issue. Willie also found evidence of a widespread wet avalanche cycle (Dec 4-5th) with slides up to D2.5.

On December 4th, observers reported whumphing collapses and shooting cracks in the snow. They also a natural slab avalanche beneath the cliff on Hinkhouse Peak (see photo below). 

If you got out, please let us know what you found in the mountains by submitting an observation.

Régions couvertes