Lawinenlagebericht

East Slopes North

Northwest Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Wet slabs and loose wet avalanches may release, and could be destructive as the slow thaw continues. Rain falling on a dry snowpack presents a challenging and complex situation, so hedge your bets and stick to low angled slopes for the time being. You're likely to find challenging travel conditions that could include a breakable rain crust, and deep mushy wet snow. 

Lawinenprobleme

  • Wet Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–2.5

    The mostly dry snowpack is going to get rained on, and we could see a variety of dangerous avalanches. As water creeps deeper into the snowpack, widely propagating slabs may become possible. Buried layers of small facets, surface hoar, and larger facets near the ground could all act as the weak layer for destructive wet slab avalanches. You may be able to trigger wet loose slides that entrain deeper snow and become large as well. In other areas, you might just find challenging travel with deep mushy snow, or a breakable rain crust. 

    The current conditions are a bit unusual, and wet slabs are tricky to predict, so give yourself an extra margin of safety with your travels. This means steering well out from underneath large, steep slopes while the snowpack adjusts. Look for recent avalanche activity as the number one bullseye of instability information. Wet, mushy, and unsupportable snow are also good indicators that wet avalanches are possible. 

    The same layers that we were concerned about with a persistent slab problem are concerning as the snowpack begins to take on water. See Willie's video below for a great example of the current situation.

    Example of a very large, wet avalanche.

    Photo: Andy Harrington

Avalanche Discussion

Washington Pass picked up about 1.8" of water equivalent since Christmas Eve with about 13" of snow, some sleet, freezing rain, and rain. Expect mostly rain with some freezing rain at lower elevations on Monday Morning. Combined with our previously low density, dry, cold and layered snowpack, this makes for a very challenging and complex situation. The extent of any recent natural avalanche cycle is still unknown with limited obs and likely poor travel. On Saturday, Willie reported lots of 6-12" storm slabs east of Washington Pass, and very weak snowpack structure near the ground. Warming temperatures at higher elevations was causing the snow at the surface to become wet, sticky, and more cohesive. Lower elevations had stayed cold with dry snow.

The mountains close to the Cascade crest have accumulated about 33" of snow since the 20th. Last Tuesday, observers near Cutthroat Lake reported two larger natural slab avalanches likely due to new snow and wind loading. At least one of these may have run on older weak layers around 7,200ft, ENE in Swamp Creek (see photo below).  Observers continue to report lots of collapsing and cracks shooting through the snow in the eastern foothills. On the 18th, an observer triggered a small avalanche on an unsupported northerly feature below treeline in the Silverstar drainage. The slide ran on the mid-November facets. The December 18th interface holds weak grains of small facets, surface hoar, and crusts on southerly aspects. You may be able to find buried surface hoar from December 8th about 2.5 feet below the snow surface.

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