Avalanche forecast

East Slopes North

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

A warm day with clearing skies will bring wet avalanches to sunny slopes. It may be easy to trigger avalanches in the recent snow, especially where overnight winds form drifts at upper elevations. Give yourself plenty of safer terrain options, and be ready to stick to lower-angle and sun-sheltered slopes.

Avalanche problems

  • Loose Wet

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

    Wet avalanches could occur naturally as the snow surface becomes moist. After a cloudy start, clearing will allow the sun to warm the snow surface. Watch for roller balls and snow falling from trees as indicators that the snow is getting moist and weak. Moist snow surfaces and wet snow that slides easily are also good indicators that you could trigger an avalanche. Watch for natural avalanches coming from overhead slopes and hazards like falling tree bombs and cornices. You'll want to exercise caution near terrain traps like above cliff bands or tight gullies where a slide could push you into hazards. 

    (11/25/2022)

    An example of small loose avalanches above Highway 20 from earlier this seaon.

    Photo: Willie Webster

  • Storm Slabs

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

    A relatively warm storm brought roughly 10-20" of snow may have created hard over soft layering in the upper snowpack. Watch for cracking in the snow, recent avalanches, and small test slopes that slide easily as indicators of instability. If you see these "red flag" signs, stick to well-supported slopes under 35 degrees. Use quick tests frequently as you travel to assess the conditions.

    Above treeline, avalanches could be bigger and easier to trigger. Avoid steep leeward, wind-loaded slopes. Pay close attention to any blowing snow or recent wind drifting patterns.  Be aware that cornices have gotten quite large and have occasionally fallen during recent storm and loading events. Stay out from under terrain with large, looming cornices and err on the conservative side if visibility is poor and you can't see the overhead slopes.

    (3/5/2023)

    A skier-triggered avalanche from last week. S, 5,600, Upper Twisp River

    Photo: Willie Webster

Avalanche Discussion

On Monday, an observer in Cutthroat Creek reported 6" of new snow and wet avalanches up to size D1.5 on south aspects. On Sunday, an observer reported a large and widely propagating slab avalanche that was about 2 feet deep in Liberty Bowl near Blue Lake Col. On Friday, large (D2) wind slabs ran on north, west, and southwest aspects around the Hairpin Valley. Some of these had crowns up to 4 feet deep, where snow sifted off of cliffs to form deeper slabs. 

On Friday, Drew Lovell reported from a prolonged period near Hart's Pass, where his concerns lay in the recent snow and alternated between loose and wind slab avalanches.  Also on Friday, Wille Webster was in the Silverstar area and found up to 3 feet of recent snow since late February. An observer on Wednesday reported a thin sun crust (likely formed Sunday) below the recent snow on southerly slopes, the crust faded away at higher elevations.  Significant snowfall and intermittent wind events since late February have brought loose avalanches or the occasional small wind or storm slab avalanche. In that time, the snowpack has gained close to 3 feet in many locations.

The Valentine's crust is 3-5 feet below the surface in the western half of the zone, including near Washington Pass, the upper Silverstar drainage, and Hart's Pass. You can expect to find it closer to the surface at lower elevations and further east in the zone. There have been numerous observations and snowpack tests indicating weak snow and poor structure below the crust. While avalanches on this layer seem unlikely, there's a chance that the weight of the new snow could initiate a slide in places where the crust is crumbly and breakable. If you're motivated to dig deep enough, you can probably still find the January 5th surface hoar. It's so deep and rounded, that it hasn't been a concern for avalanches in over a month near Washington Pass. We have less of an understanding of the progression of these layers east of Mazama and the Twisp River drainage.  

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