Avalanche forecast

Olympics

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Drier weather, soft snow, and a little sunshine will make the mountains feel very inviting. However, a recent storm and a known buried weak layer of snow should keep conditions dangerous. You could trigger an avalanche on steep open slopes, especially where the wind drifted the snow deeper.

Avalanche problems

  • Persistent Slabs

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

    We think the weak layer we've been tracking - buried surface hoar - has become a persistent problem. A 1-2 ft slab lies above surface hoar buried 12/8. This slab/weak layer structure became quite reactive last weekend. It was the culprit for a D1.5 natural avalanche (12/10) in Poma Bowl and a D2 remotely triggered avalanche on a NW aspect at 5200 ft (12/11). We have no observations from the Olympics since 12/11, so we don't know how this layer has evolved during a period of generally cool high pressure. What we do know, is that you don't want to get caught in one of these avalanches. Persistent weak layers such as surface hoar can remain reactive long after a storm. You can trigger surprising avalanches from slope angles as shallow as 30 degrees, remotely trigger a slope from nearby, or experience much wider slab propagation than you expect. Until we have a better handle on the problem, it is wise to adopt a more conservative approach than you normally would due to the higher consequence (albeit reasonably low probability) of the problem. If you travel in avalanche terrain, stick to slopes less than 30 degrees. For those experienced travelers, only consider easing into terrain up to 35 degrees after performing multiple ECT or shovel tap tests and confirming a lack of propagation on the weak layer. 

    Given the amount of sunshine Hurricane Ridge has experienced since the last storm, healing of the weak layer would be much more likely on SW-S-SE aspects, while colder shaded aspects should be treated with utmost caution.

    (12/10/2022)

    Natural soft slab running on surface hoar. Poma Bowl, Hurricane Ridge.

    Photo: NPS Olympic Rangers

Avalanche Discussion

These are not normal conditions at Hurricane Ridge and you can't expect the instabilities to diminish rapidly with time after the storm. Similar snowpack conditions have been reported in the Cascades with reactivity remaining in the southern Washington Cascades and Mt. Hood areas. Undoubtedly, the conditions have evolved significantly since we last received observations over the weekend and the reactivity of the layer may differ from expectation. However, uncertainty warrants an especially cautious approach. You can use snow profiles and snowpack tests to confirm the presence of this layer, but they don’t prove its absence. 

This is the time when we really need your observations. If you head out, did you find the slab/weak layer structure intact? Could you see a thin, grey line? Was it reactive? We're also interested in tracking snow surfaces for what might be buried when snow from the next storm starts trickling in over the weekend.

You may find recent winds have formed small wind slabs that could be reactive on very steep, unsupported slopes near ridgelines. If you head onto south-facing slopes, the 9500 ft freezing levels forecast for Hurricane Ridge are much higher than we've seen in a while. While these slopes have already seen plenty of sunshine, it would be prudent to move to cooler, shaded slopes if you see rollerballs or wet loose avalanches.

Other observations from Hurricane ridge this week show small cornices, scoured ridges, and sculpted snow features all telling the story of the recent winds. 

Even though it feels like winter, plenty of exposed and shallow buried obstacles still exist to make travel more challenging and potentially dangerous.

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