Bulletin d’avalanche

Olympics

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 8 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Anywhere rain falls on previously dry snow, expect the potential for wet avalanches. Above the snow line, expect to find reactive drifts just in the lee of ridgelines. If you encounter either of these problems, steer around wet, sticky snow or lens-shaped pillows where you can trigger an avalanche.

Problèmes avalancheux

  • Loose Wet

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

    We don't expect that that 1/4 inch of rain on snow will cause widespread wet loose activity because the snow has settled significantly and crusted over on many slopes. We're expecting around 0.25" of rain to fall at lower and middle elevations around Hurricane Ridge. Expect more in the southern Olympics. The more rain saturates the snow, the more an avalanche has available to entrain.  Generally small human-triggered or natural avalanches are possible. Therefore, watch for steep slopes that may be above you. While snow could destabilize on shaded aspects at lower elevations, snowpacks are unlikely to produce avalanches that will harm you.

    Most wet loose avalanches run the length of a slope steeper than 35 degrees and fan out as they descend. If you head to upper elevations, you may encounter wet, heavy snow accumulating. You could push this snow on top of surface crusts and once it gets moving, it will entrain the snow beneath it. 

    Example: A natural wet avalanche.

    Photo: Dallas Glass

  • Wind Slabs

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

    With 2-3" of new snow falling at upper elevations and increasing, but generally light SW winds on Friday, the wind slab avalanche concern would typically be minor. However slabs could overly weaker snow surfaces that may be preserved on some upper elevation shaded aspects above around 6000-6500 ft. This could produce small slabs that propagate more widely than you expect and catch you off guard. If you venture up there, dig down to the new snow/old snow interface and look for a thin gray line (surface hoar) or sugary facets. We're not sure how patchy or widespread these weak surfaces will be or whether they will get buried intact, but keep them on your radar and report back if you find them.

    Example: A touchy, but small wind slab that overlies weak snow above a crust.

Avalanche Discussion

Olympic NPS rangers ventured out to Hurricane Hill to enjoy a warm, cloudy day with temperatures in the mid-30s, rounding out an unusually pronounced late-December ridge of high pressure. This has deflated the snowpack since last weekend. Solar aspects have a friable 1 cm thick crust. Crusts are barely supportable in wind-swept areas. On N aspects, they encountered heavy, smooth powder, with a bit of wetting in upper half inch of the snowpack. Of note, they found 2-3 cm of near-surface facets on low-angle or flat slopes near the top of Hurricane Hill and patches of 3 mm feathery surface hoar in open areas surrounded by trees on the ridgeline out to Hurricane Hill. You're likely to find the 12/24 crust within the upper foot of the snowpack, likely averaging 6-8 inches down on a shaded aspect.

Glide cracks have opened in some parts of the Cascades. If you encounter them, rain will make them more likely to release. If you do see a brown frown, don't linger underneath it.

The snow last week drastically improved coverage and travel conditions. Even still, open creeks, random holes, and grabby bushes should remain on your mind.

Régions couvertes