Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Avalanche danger is slowly decreasing, but you can still trigger one on steep slopes holding slabs of wind-drifted snow. Deep, unconsolidated snow and tree wells might be the greatest danger you encounter on Sunday. 

Avalanche problems

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–1.5

    Cold, light snow at the surface is easy to push around and get moving in steep terrain. While mostly small, loose snow avalanches can pick you up and carry you downhill into a tree, gully, or other hazards. Be aware of how much snow is moving with you if descending steep terrain.

    The sun hasn’t had much of an effect the last few days, but when it does eventually come out for real and warm up the snow surface, be ready for a round of loose snow avalanches. Look for rollerballs and small loose snow avalanches if the sun makes and appearance. Warming can also form a reactive slab from loose dry snow at the surface.

    (2/26/2024)

    Dry loose avalanches in non wind-affected snow.

    Photo: Zoë Vernon

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Another day of gusty winds made for another day of wind transport and slab formation. Wind speeds and fresh slab formation should be lesser on Sunday, so you will mostly deal with slightly stale, day-old slabs. Cornices grew larger during the last few rounds of storms and could be quite fragile - give them plenty of room when traveling along ridgelines.

    Look for variations in snow appearance, texture, and stiffness to determine which slopes are most likely to hold wind slab. Stomping on tiny cornices and other features shaped or loaded by wind can help you determine reactivity. If you observe active wind transport, be ready to find more reactive slabs. When in doubt, use a lower-angled line to navigate around wind-loaded slopes.

    (3/2/2024)

    Skier-triggered slab avalanche in wind-drifted snow. Southwest aspect of Herman at about 5100'.

    (SS-AS-D1-S)

    Photo: Kameron Decker Harris

Avalanche Discussion

Preliminary Report: An avalanche accident occurred on Friday, March 1, near Darland Mt in the Ahtanum Meadows area. Two snowmobilers were involved in the slide. One rider was fully buried and killed. The avalanche occurred around 6600ft in a generally east-facing bowl. NWAC staff will visit the accident site on Saturday. Our deepest condolences to the family, friends, and community.

The setup for deep snow immersion or disappearing into a tree well is currently about as dangerous as it gets.  Many feet of light and unconsolidated snow combined with previously low snow cover have created countless traps that seem fully covered at the surface.  Avoid traveling close to trees, have a partner, and keep them in sight at all times.  A tree well was responsible for a fatal accident in backcountry terrain on Friday.

Observers reported a handful of small, human-triggered avalanches in terrain with recent wind loading on Saturday. While the overall wind direction was from the south, swirling, gusty winds loaded a variety of aspects around the Baker BC. Other signs of instability consisted of fresh wind-drifted features easily cracking and failing 8-12” deep and some small loose dry avalanches triggered on shorter, steep slopes. While the snow is still deep, it’s settled enough to make for easier travel going both up and down the hill.

The last storm left behind crowns and debris from natural avalanches on many northerly facing, upper elevation start zones around the Baker BC. Similar avalanche activity is suspected from other parts of the forecast zone, but observations were lacking as of Saturday afternoon. Layers of weak faceted snow that failed under extreme loading during the latest storm are the likely culprit. 

No human-triggered avalanches related to faceted snow or crust-facet combinations have yet to be reported from West North since Tuesday, February 27th. On the other hand, avalanche forecast zones to the south (West South), the entire east slopes of the Cascades, and also to the north (Canada) have legitimate persistent slab problems with continued avalanche activity related to similar layering.

Now buried under several feet of new snow, it’s unlikely - but not impossible - a person could trigger a deeper avalanche. The best chance would be on northerly aspects at upper elevations, and where the snowpack is also shallower over the Early February Crust. Locations farther east in the zone may have a better-developed weak layer and less snow over the crust. 

Don’t ignore signs of instability like whumping or shooting cracks - they are the best sign that you could trigger one of these in steep terrain. Bigger loads like a falling cornice, smaller avalanche or group of people might trigger one of these larger avalanches where a single person would not.

In wind-sheltered areas, the snow that has fallen since the 24th is generally right-side up, with intra-storm layers showing little reactivity. A recent snowpit (photo) in the Baker BC showed nearly 5’ of new snow with over 6’ on top of the Early February Crust. Wind-loaded slopes representative of ridgeline start zones have 8' or more over the same crust.

 

 

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