Bollettino valanghe

Central Cascades

Central Oregon Avalanche Center
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Pericolo valanghe

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Limite del bosco
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In sintesi

Large human triggered avalanches will be possible in wind drifted snow near and above treeline. Wet loose avalanches will also be possible on sunny slopes, especially at lower elevations as the day warms up. Look for signs of unstable snow, and if in doubt, stick to slopes under 30 degrees.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    On Saturday in the alpine I observed sustained strong winds moving a lot of snow primarily from the east. I also found small wind slabs on south facing slopes and cracking in wind drifted snow on west and northeast aspects. Winds were also changing directions and became quite varible in the afternoon.

    With the variable wind directions and cracking observed on several aspects, wind slabs will continue to be possible on all aspects near and above treeline. Most avalanches will likely be small (D1); however, isolated features that collect snow could lead to larger slabs that could bury a person (D2).  Larger avalanches could also occur on a melt freeze crust with weak snow on it. See the Forecast Discussion below for more details.

    Look for clues such as wind drifted snow, pillow like features and textured snow surface. Other red flags are blowing snow, cracking, collapses and recent avalanches. Consider using safe test slopes on similar aspects and elevations to assess the snow before riding. Rememeber that any slope where the wind can freely blow snow can see slab formation even at lower elevations (i.e. open steep slopes and burn areas).

     If in doubt, stick to slopes under 30 degrees.

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    With temperatures reaching above freezing, be on the lookout for wet loose avalanches. This will be more likely in areas at lower elevation like Santiam Pass which will see a high of 44F on Sunday. Steep sunny slopes are usually where we can find this avalanche type.

    Look for clues such as pin wheels, wet/slushy snow and snow melting off trees. You can also utilize small/steep test slopes to assess for this problem. Use timing to avoid this problem, and if you see any signs of wet loose activity, move to slopes with less solar effect.

Avalanche Discussion

On Friday a large skier triggered avalanche was reported near treeline on a NNE slope. This avalanche ran on the old melt freeze crust with some weak snow  (1mm facets) on top of the crust layer that was buried 18". Facets were also found on Saturday at 8,000ft on a northeast aspect on this same melt freeze crust down 47".  The depth of this old crust layer will vary depending on how much drifted snow is sitting on it. With the presence of this weak snow, slab avalanches may run larger and propagate farther than expected, especially on northern aspects in the alpine.

We have only had one report of an avalanche on this layer, and the distribution is likley variable. However, your best bet is to use your avalanche probe to find this crust layer and dig in the snowpack to look for weak snow on top of the crust. I often use compression tests and extended column tests to look for these layers. Whenever there is uncertainty in the snowpack (like what we have with this layer), I often dial back my terrain choices and stick to lower angle slopes and slopes with less consequences.

As always, keep cornices in mind if you travel to ridge tops. As we see warmer temperatures, cornices will be easier to break and often break back farther than expected. Don't hang out under cornices, and  give them a wide berth.

Thank you all for your observations! 

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