Bulletin d’avalanche

Olympics

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You can trigger small avalanches anywhere you find active wind or recent wind loading and a steep lee slope. Low-density dry snow abounds on cooler, shaded aspects and may form fresh drifts as winds increase on Saturday. Use simple hand shears and small wind loaded test slopes to evaluate slab reactivity and bond to the underlying snow or crust interface.

Problèmes avalancheux

  • Wind Slabs

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

    SW winds will increase into the moderate range Saturday afternoon, forming more reactive slabs by the end of the day. Although sun-exposed aspects will have a crust limiting snow available for transport on these aspects, shaded slopes have plenty of snow ripe to move. You may find slabs have formed on the leeward side of ridges, under cornices, in gullies/couloirs, and cross-loading alpine features. Active transport will be your best clue to visually identify which slopes are loading up, but settlement under your planks as you travel should be a sound indicator as well. If visibility deteriorates, you should consider reducing your terrain selection. Steer around steep, wind-loaded slopes and consider evaluating slab layering down to and including the 2/20 crust. Slabs may have formed over very low-density snow, wind-pressed surfaces, crusts, or even very small weak snow grains formed during the last few cold clear nights. Crusts and weak snow grains at the interface could make for small wind slabs that would likely take you for a ride where 6" or thicker. 

     

    (2/23/2023)

    Cracking on wind pillows at ridgeline

    Photo: Sam Siemens-Luthy

Avalanche Discussion

Observers reported fantastic riding conditions on Thursday and Friday. 2-3" of fresh snow had fallen since 2/22 with very low density "snow flurries" continuing to pile up.  8-10" of snow now sits over the 2/20 crust.  Although winds have been shifting direction, more snow loading appears to have occurred on E aspects since the last storm. These older drifts do not generally appear to be a concern moving forward.

Although the snow has settled somewhat, dry loose avalanches may continue on slopes 40 degrees and steeper. This can be consequential where it could push you over a cliff or into unwanted obstacles. Sunshine warmed snow surfaces on W-S-E aspects, forming plenty of loose avalanches and a crust by late Friday. This crust, combined with increasing clouds and wind should limit wet loose avalanche potential on Saturday. 

Snow pits at 5000 ft on an E aspect on Thursday show two crust sandwiches (see media gallery). The upper one was formed warmer daytime temperatures 2/20 and 2/19 with some snowfall in between. Snowpack tests show a slight weakness just below the 2/20 crust proper, but it does not appear concerning. The lower double crust formed around 2/13. The layer of snow between the two crusts has consolidated significantly since last week.

Maintain awareness for changing weather on Saturday as winds increase and the snow starts to fall late in the day. If the snow arrives earlier than we expect, consider moderating your terrain selection further. 

Régions couvertes