Bulletin d’avalanche

West Slopes North

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 might see wind slab or wet avalanches - or both - depending on where you go in the mountains. Steer around areas of wind drifted snow in steep, upper-elevation terrain. Give sunny slopes some room if you see signs of instability like rollerballs and pinwheels. Unusual avalanche activity in the last week is still a factor in mountain travel. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2.5

    Danger from wind slabs will come in two flavors this weekend. The variety that should be easier to anticipate is recently formed slabs from strong winds and 4-8" of snow early Friday morning. If you trigger one it would probably be on a convex rollover, gully wall, or around a cliff or rocky outcropping.

    Key into the pattern of wind loading by using scoured snow surfaces, cornice-like features, and changes in snow texture and depth to figure out where smaller slabs might lie in wait. A few inches of soft snow might hide signs of wind loading. These avalanches should be small but still have big consequences in terrain with cliffs, rocks, or other hazards in the runout. 

    There are also slabs you are much less likely to see but be more likely to ruin your day (obs, obs). They were not typical wind slabs but occurred in wind loaded terrain. So far the common terrain characteristics for these avalanches are above treeline and wind loaded.

    Pits may or may not do much to help you gauge if the slope in front of you is good to go. If you do dig look for and test a layer of facets or graupel above a melt-freeze crust down anywhere 1-4'. If you head into this sort of terrain you are just assuming a little more risk than usual.

    (2/8/2023)

    Large snowmobile triggered wind slab avalanche on the south side of Baker. East aspect at 6300'. Triggered from red circle. No one was caught.

    Photo: NWAC Public Obs

  • Loose Wet

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

    Saturday should bring more consistent sunshine to the Cascades. Temperatures are not necessarily warm, but light winds won’t do much to keep the snow surface cool either. Below treeline terrain was mostly rained out this week so there shouldn't be much soft loose snow to react with warming. Consider a higher likelihood of wet avalanches if you find more than a few inches of soft new snow below treeline. 

    Look for pinwheels or balls of snow rolling down the slope as telltale signs of warming. Small wet loose avalanches could be a sign larger ones are not far behind. Slopes on the south half of the compass are likely to feel heat from the sun. 

    Wet loose avalanches and rollerballs in 2021 on the south side of Herman.

    Photo: Steve Gately

Avalanche Discussion

Snowfall early Friday put down just enough to keep folks from getting hung up in the rain crust underneath. 3-5" of new snow over rain crust with moist snow below were reported from Canyon Creek. Fresh avalanche activity was limited to small slabs up to 10" deep triggered with avalanche mitigation work. No other avalanches were reported from anywhere in the zone other than large ones from earlier in the week. Rainfall to 5000' and a cycle of natural loose and slab avalanches were observed Thursday. 

There was lots of variability in the snowpack prior to the big storm. Some places were scoured down to near the MLK crust while others sported a stiff wind slab. Some areas accumulated new snow which in turn faceted during cold temperatures. The storm also produced different patterns of natural avalanche activity. The backcountry terrain around Mt. Baker Ski Area saw a widespread avalanche cycle while other areas saw less natural activity.

Régions couvertes