Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

Very dangerous avalanche conditions exist due to wet, heavy snow and rain falling with a gradual warming trend. Very large avalanches may run from upper elevations down to valley bottom with wet debris, and wet slabs may occur on steep slopes in the foothills. Friday is a good one to stick to flat terrain, well away from steep slopes.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–3

    Another foot of heavy, wet snow may fall at upper elevations by the end of the day on Friday. The snowpack beneath is drier and low density, so this makes for upside-down storm snow. To complicate matters, slabs may be the depth of the new snow, but in isolated areas deeper, weak layers could make for surprising and much larger avalanches if they step down. Slides could run down from upper elevations and cover access roads.

    Make sure to stay off of steep slopes, and well out from underneath larger terrain features as the storm continues.

    (1/8/2023)

    Example storm slab in terrain below treeline.

    Photo:

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    Wet slabs and wet loose avalanches should be expected as the snowpack takes on rain. There was a round of wet slides earlier in the week that were taking the entire snowpack out to the soil, and we could see more of these occur overnight into Friday. As the snowpack becomes wetted by rain up to around 5,000ft, expect these to be commonplace on steep slopes. Slides could become large and gouge to the crust from Christmas. 

    Stay off of and out from underneath steep slopes, especially at lower elevations. 

    (1/11/2023)

    Large wet loose and wet slab avalanche in the Methow Valley from earlier in the week. 

    Photo: Willie Webster

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    The weight of the new snow is likely stressing buried persistent weak layers. You're most likely to find these outside of wind affected areas, in sparse trees and on north to east aspects and perhaps further east in the zone. We suspect weak snow surrounding a crust from Christmas, and possibly buried surface hoar from around January 4th. A skier triggered a large slab on a north aspect at 4,800ft near Silverstar, so we should take this as bullseye evidence. You can look for long shooting cracks as you travel, and check for planar failures with a variety of tests. Both parties that have triggered slides in wind sheltered terrain reported no signs of instability beforehand, so the absence of information doesn't necessarily mean stability.

    Hedge your bets by staying off of, and well out from underneath steep slopes in terrain described above, especially as snow continues to pile up, and temperatures warm. 

Avalanche Discussion

Temperatures should continue to gradually warm up overnight Thursday into the day on Friday. Snow should keep piling up at higher elevations, but is likely becoming quite heavy and wet. The gradual warming trend and continued precipitaton are expected to lead to a natural avalanche cycle. Slides could become large and destructive from higher elevation slopes with wet, chunky debris. Friday will be a good one to stick to flat terrain, well away from big, steep mountainsides but also small, steep areas like terrain trap gullies.

Josh made it up into the Twisp drainage and reported subtle upside-down snow by 2pm. They were able to trigger small loose dry avalanches at 4,900ft. At this same elevation on a northerly aspect they found tilt tests to fail down about 10" on an interface from around January 9th. The Christmas crust was down about 2ft, and they got sudden planer test and propagating test results on it (CTM SP, ECTP H). A report of a large ski triggered slab on a north aspect at 4,800ft came in from the Silverstar Creek area on Tuesday. The slide did not occur in wind affected terrain, but in sparse trees. This is all information to take into account as the storm continues, and folks hunt out better visibility and areas that are typically considered safer.

Other avalanches of note: On Monday, Willie reported two small soft slab avalanches hit the closed Hwy 20 in the Liberty Bell group on Monday morning. Winds were strong with intense blowing snow in the morning, then skies broke and the wind calmed down. Shallow storm slabs were easily triggered about 8" down. Tests showed potential for failure down about 1ft and 1.5ft on large, preserved stellars.On Sunday, a party reported triggering a small slab near Varden Creek on a north aspect at 6,000ft. The skier that triggered the slide was the fourth on the slope, and got carried a little ways but was luckily ok.  WSDOT forecasters reported a wet avalanche that gouged to the ground near the town of Methow. On Saturday, an observer near Twisp reported a mix of snow and rain with a similar avalanche gouging to the ground.

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