Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

A quick moving storm will bring up to 12" of light new snow and periods of strong wind. Identify and avoid steep terrain where the wind is building slabs of dense, stiff snow or anywhere the new snow is poorly bonded to layers below.

Avalanche problems

  • Wind Slabs

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

    Expect to see new wind slabs on Thursday with potentially dangerous conditions developing in the alpine. Fresh wind slabs will once again build on leeward slopes. Identify areas of wind slab using visual clues like wind scoured snow surfaces and cornice features that point in the direction of wind loading. Poor visibility may make it difficult to identify wind loaded slopes in the morning - err on the side of caution when traveling near avalanche terrain and build this uncertainty into your plan for the day.

    (12/29/2021)

    Wind eroded snow surface on Shuksan Arm.

    Photo: Lee Lazzara

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Periods of intense snowfall Thursday will build soft but reactive slabs, especially where accumulating on a weak snow surface. The danger in wind sheltered terrain will likely be greater in the southern half of West Central where more snowfall is forecast. In addition, observers around Stevens Pass reported widespread surface hoar and facets on all aspects. These weak snow grains could inhibit the bond between the old snow surface and new snow layers building above. Any steep slope is suspect where you find 12” or more of new snow. Use hand shears and other simple tests to evaluate new snow layering. Factor in the consequences of getting caught in even a small avalanche in lower elevation areas where there could be tree wells, open creeks, or gullies in the track or runout 

     

    (12/22/2021)

    No shovel required . . . hand shears are a fast and simple test to evaluate layers in the upper snowpack. 

    Photo: Andy Harrington

Avalanche Discussion

Clear skies and cold temperatures dominated the West Central after nearly a week of steady snowfall before and during Christmas. Despite receiving 3-5' feet of snow in favored locations, most reported avalanche activity in surrounding zones was limited to shallow, human triggered storm and wind slab avalanches.  Varying winds the last few days created new, small wind slabs on a variety of aspects. More noteworthy observations include two large avalanches triggered during avalanche mitigation work in the West North and large natural avalanches in alpine terrain in Snoqualmie and Stevens Passes and on Mt. Shuksan. These were likely part of a natural avalanche cycle during the period of extended snowfall. These outliers indicate that layers deeper in the snowpack like the Solstice crust are still in the back of our minds when it comes to upper elevation terrain. While triggering such an avalanche is unlikely, it's not impossible in extreme terrain or with a large trigger like a smaller avalanche or cornice falling from above.

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