Bulletin d’avalanche

East Slopes North

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

Points saillants

You may be able to trigger wet avalanches as snow surfaces get warm and wet. Give yourself options to move to lower-angle or shadier slopes to avoid triggering wet slides. Loose avalanches are also possible on steep, shaded slopes at upper elevations.

Problèmes avalancheux

  • Loose Wet

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

    Expect more sun and warmer temperatures than the last couple of days. Wet avalanches may be easy to trigger and could occur naturally. If the surface snow starts getting moist or you see rollerballs, expect wet avalanches could follow. Avalanches should mostly be small as frozen crusts lie just under the surface of many sunny slopes. Build options into your travel plan to stick to shadier or lower-angle to avoid wet avalanches. Time your trip to be off of slopes before the sun makes the surface wet and weak.

    On steep, northerly slopes at upper elevations, you can trigger dry loose avalanches. Use caution around consequential features and terrain traps like cliffs, rocks, and gullies. Here, loose avalanches that wouldn't normally pose much threat could have dangerous consequences.

    Rollerballs shedding below rocky features are indicators that small wet loose avalanches may not be far behind on similar slopes.  

    Photo: Robert Hahn

Avalanche Discussion

Before conditions cooled on Thursday, the recent spring weather really affected the old snow surface. A crust of variable thickness formed on E-S-W aspects high into the terrain due to sunshine and in shadier areas at lower elevations because of warm temperatures. Higher northerly aspects still managed to preserve cold dry soft snow over the past week. 

The Valentine's crust is 3-5 feet below the surface in the western half of the zone. You can expect to find shallower at lower elevations and further east. There have been numerous observations and snowpack tests indicating weak snow and poor structure exist below this crust. It's suspected to have been a weak layer for some of the very large avalanches at the end of the last storm cycle. On Sunday, Willie Webster went to the far eastern part of the zone, north of Tiffany Mountain. He found a much shallower and more faceted snowpack than what we tpically see west of Mazama.

Régions couvertes