Lawinenlagebericht

Stevens Pass

Dec 21 – 22, 2018Northwest Avalanche Center
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Archiviert · abgelaufen 8 years ago

Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Recent blowing snow and strong winds have maintained heightened avalanche danger at upper elevations. Steer around wind drifted features near and above treeline and minimize your exposure to large steep slopes and avalanche paths. Only expose one group member at a time to slopes steeper than 35 degrees and identify safer areas to stop and regroup.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1

    Steer around wind loaded features and areas where the snow deep and thickly pillowed on slopes steeper than 35 degrees. Use caution on leeward slopes just below ridges.

    Avalanches will be easier to trigger as you climb higher in the mountains. Strong wind and new snow from the past 3 days have formed slabs near and above treeline. If you trigger an avalanche in wind drifted snow, dig into deeper layers, resulting in a very large and dangerous deep persistent slab.

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2

    You could trigger avalanches in the eastern portion of the zone and on steep, shaded slopes facing west through north through east. While deep persistent slabs are generally difficult to trigger, they are also hard to predict. They will give few warning signs before releasing. If you travel over the wrong spot, you could trigger a very large and dangerous avalanche. The best way to reduce the risk of this is a low likelihood, high consequence scenario is to minimize your exposure to terrain capable of producing large avalanches:

    -Limit the amount of time you spend on or near slopes 35 degrees and steeper.

    -Put an extra buffer of terrain between where you travel and where avalanches could start.

    -Stay well out from under large avalanche paths and identify safer areas to stop and regroup.

Snowpack Discussion

Regional Synopsis: December 19, 2018

Why has the avalanche danger been so high for so long? Two reasons: A very active and wet weather pattern combined with a widespread persistent weak layer.

For perspective, the approximate snow totals from 12/9-12/19 are:

  • Mt Baker: 102”

  • Washington Pass: 55”

  • Stevens Pass: 76” mid-mountain

  • Snoqualmie Pass: 68” mid-mountain

  • Crystal Mountain 70” Green Valley

  • Paradise: 78”

  • Mt Hood Meadows: 44” mid-mountain

  • Olympics: 48”

In many areas, a layer of buried surface hoar and/or weak sugary facets was buried on December 9th. This layer has been the cause of numerous natural, explosive, and skier triggered avalanches. As this layer gets deeper it gets harder to assess. In short, the scenario is tricky and getting more dangerous by the day.

Higher snowfall totals along the Hwy 542 corridor/Mt Baker area have driven several avalanche cycles during this period. Loading from recent storms has been more incremental to the east and south of the Mt. Baker area, so we have not yet experienced a widespread cycle in other areas.

When will we reach the breaking point? It’s hard to say. What we do know is we have a deep weak layer, reports of very large explosives triggered slides at Mission Ridge and Crystal Mountain, and more storms on the way.

Be patient and continue to stick to lower angle slopes with nothing above you.  This is a good time to avoid areas where avalanches can start, run, and stop.

We’d like to thank all of you who have sent NWAC your observations. If you are out in the mountains, let us know what you see.

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