Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
1 · Faible
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 find shallow wind slabs below ridgelines at upper elevations.  Use caution on steep slopes with recently drifted snow. You can still find drier snow on shady aspects and a crust of variable thickness on most other aspects.

Problèmes avalancheux

  • Wind Slabs

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

    Once again the forecast doesn't favor the East North zone for enough new snow or wind slab to warrant much concern about fresh wind slab development.  However, you may still find and trigger shallow wind slabs formed recently. These should primarily be located near exposed ridges and along the base of cliffs closer to the Cascade crest. Even though we expect these slabs to remain small, they might surprise you and trigger easily over a variety of older surfaces. Don’t let them catch you by surprise and send you over a cliff or other terrain trap. 

    It's a big zone and if you find yourself in an area that has received a few inches of new snow, keep an eye out for small wet loose avalanches.  On steep sunny slopes, it won't take long for sunshine to move new snow downhill in the form of rollerballs or pinwheels.  Small wet loose avalanches are possible if those sunbreaks stick around longer than expected.  If you find yourself in this situation on Saturday, move to a shadier cooler aspect or lower-angle terrain.  

    (2/18/2023)

    Signs of wind loading to look for Saturday.

    Photo: Dallas Glass

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.  While not much new snow has fallen since Thursday, be aware of refrozen chunks of rollerballs or small wet loose avalanches that may be lurking under a shallow fresh coating of new snow. 

Colder weather will lower the risk of glide avalanches, but they can still release days after conditions begin to cool.  You can deal with this unlikely but serious avalanche problem by steering clear of areas below crevasse-like cracks.

While this storm shouldn’t be enough to wake up any deeper weaklayers, we are still tracking a few interfaces in the snowpack. 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. We have less of an understanding of the progression of these layers east of Mazama and the Twisp River drainage.

Régions couvertes