Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

Sat
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Triggering an avalanche on Friday will be unlikely. The culprit the forecasters have been discussing over the last week is a layer of buried surface hoar on northerly and easterly facing slopes and it is becoming increasingly stubborn to non-reactive. If you are hunting out those obscure, steep, and committing lines in extreme terrain, it is still not a bad idea to dig in and evaluate the snowpack before dropping in.

Avalanche problems

  • Persistent Slabs

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

    The persistent slab problem is related to a layer of buried surface hoar that has become more stubborn day by day. On Thursday no propatation was found during snowpack testing on this layer in northerly terrain at multiple locations; typically where we would expect it to be most reactive. In snow pits, the surface hoar crystals have been found to be laying down and beginning to degrade. In the last few days no avalanches or signs of unstable snow such as collapses, whumphs, or cracking in the slab have been observed. 

    The weak layer has been found anywhere from 40 - 60 cm (16 - 24") below the surface. It is still out there and pretty easy to find in snow pits. It is too early to take it off the problem list entirely, if for no other reason than to keep in in mind. In rare isolated terrain there is a low likelihood of triggering an avalanche that could be large.

Avalanche Discussion

In Central Oregon, we do not get many persistent weak layers but it does happen from time to time. December and early January is when we typically see them. With time, they usually become non reactive. Compared to other regions in the mountain west, our persistent weak layers do not persist for long. Also, with time after the last addition of snow, these layers tend to quiet down and become less active. It is possible that when the next big  storm comes through and adds weight to the upper snowpack, this layer could 'wake up' and become active again. 

On Thursday, new surface hoar formation was observed on the top of the snowpack on west, and north facing slopes near and below treeline. Anything can happen before the next round of storm snow comes in. Surface hoar can be destroyed by wind and sun and may or may not stick around long enough to become buried by new snow. We will keep an eye on it between now and then. It is not a concern on the surface, only when it becomes buried. 

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