Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Your risk of triggering a slab increases throughout the day as strong winds redistribute fresh snow. Slabs will be more reactive above treeline where the new snow may bond less well to firm surfaces. Blowing/drifting, punchy snow, or a poor bond to the old snow interface all serve as a reminder to steer around unsupported wind-loaded slopes steeper than 35 degrees.

Problemi valanghivi

  • Wind Slabs

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

    Slabs will build from scratch as snow moves in and winds increase Saturday night through Sunday. Strong winds will efficiently redistribute the expected 6" of new snow that falls above 5000 ft to form slabs that could be approaching large size by the end of the day. At lower elevations, the rain will fall, but as you transition to dry snow, begin monitoring the average height of new snow and the thickness of wind-loaded deposits. Wind-scoured slopes highlight heightened danger on the opposite side where the winds will be blowing and drifting the snow to form lens-shaped pillows. Steer around these drifts and pillows on slopes steeper than 35 degrees. Frequent rapid slope tests and shallow hand pits can help you identify the bond with the underlying crust and upside-down/unstable layering within the drifted snow.

    Example: Fresh cornices and loaded slopes near ridgelines. This shallow slab was likely in wind-loaded terrain.

    Photo: Dallas Glass

Avalanche Discussion

Much-needed snowfall is returning to Hurricane Ridge Saturday night and Sunday after winter took a break around January 11th with temperatures largely staying above freezing for 2.5 weeks. The recent mild weather took a toll on the snowpack. Glide cracks have opened up over this stretch (see photo gallery) and may present an objective hazard on convex rollovers as blowing snow obscures visibility on Sunday. Shallower sun-exposed aspects and ridges have melted back significantly exposing grass and rocks. Avalanche activity ground to a halt in the past week as the upper snowpack transitioned to a morass of crusts. On Saturday, observers chiseled out some snow pits and reported 20 inches of mostly knife hard crusts above rounded grains. A large-grain melt form layer down 34 inches has the potential for reactivity, but this is not a concern at this time given strong bridging from the ice in the upper 20 inches of the snowpack. Isolated shallow drifts deposited with a skiff of snow on January 20th sit on top of the crust and have faceted on shaded aspects. A wafer-thin crust covers these drifts. While these are not a problem near treeline at Hurricane Ridge, it is possible that they could serve as a weak layer on shaded terrain at the highest elevations or in other parts of the range.  

Below the 4000-5000 ft rain/snow line, we expect the snowpack to be well suited to handle the water. However, if you find wet, slushy snow you can sink into deeper than your ankle, expect you can trigger small wet loose avalanches on steep slopes. Isolated glide avalanches may become reactive once again on steep slopes and are most likely in areas where a glide crack has already opened up.

2021-22 Forecast Schedule: Avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays. During the week when the Hurricane Ridge road is closed, forecast information will be updated daily to include expected conditions and relevant travel advice under the No Rating label.

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