Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Expect a cooler, windier day with a trace of new snow. You can easily trigger loose avalanches in the recent snow. You may be able to trigger more dangerous slab avalanches, where winds form drifts at upper elevations.

Avalanche problems

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    There's still plenty of soft, dry snow in a variety of terrain. You can easily trigger point releases in on steep slopes that could run fast and accumulate enough snow to be dangerous if you're not paying attention.  You'll want to exercise caution near terrain traps like above cliff bands or tight gullies where a slide could be dangerous. You may find wet avalanches on steep, sunny slopes. Watch for roller balls and snow falling from trees as indicators that the snow is getting moist and weak. Watch for natural avalanches coming from overhead slopes and other hazards like falling tree bombs and cornices that could trigger avalanches.

    (3/9/2023)

    Dry loose sluffs from last week near Harts Pass.

    Photo: Drew Lovell

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    While there hasn't been much previous wind transport of the recent snow, westerly winds are forecast to increase on Wednesday. There's plenty of snow available to form fresh slabs. Watch for plumes of blowing snow to point to the loaded slopes. 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. 

    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 loading and warming 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.

    (2/17/2023) Look for blowing snow as an indicator that fresh wind slabs are forming. Photo: Drew Lovell

Avalanche Discussion

On Tuesday, observers reported triggering a number of fast-running sluffs in the recent snow. 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. 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 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. Avalanches on this layer are unlikely. 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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