Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

Very mild temperatures are beginning to create wet and weaker snow surfaces. You could trigger small wet loose avalanches and rollerballs on steep sunny slopes and maybe even on shaded ones. Use normal caution, exposing only one person at a time to avalanche terrain. 

Avalanche problems

  • Loose Wet

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

    Snow surfaces may not refreeze very well overnight with warm temperatures and cloud cover. Expect wet snow on southerly aspects and moist, sticky snow over drier snow on shaded slopes. As the day warms you may find areas where you could easily trigger rollerballs and small loose wet avalanches. Cornices are beginning to sag, and may fail sporadically with the warm temperatures. 

    If you observe wet, gloppy snow and rollerballs, expect you could initiate wet loose avalanches on very steep slopes. Keep in mind overhead hazards or other areas where getting caught in even a small, wet avalanche may hold increased consequences. If you find the right combination of steep, unbroken slopes at the wrong time, slides could run further than expected.

    (2/4/2022)

    Example small wet loose avalanches.

    Photo: Public Observation

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–2

    A previously problematic layer can be found 1.5-2ft below the surface. There is uncertainty how very warm temperatures and wet snow may influence chances for persistent slabs on Thursday. Weak sugar-like facets (or surface hoar) sit above, and sometimes between, a crust and was buried by a storm in late January. The weak layer has been consistently found on NW-NE aspects between 4,000ft and 4,700ft. This low elevation band produced startling collapses and shooting cracks a week ago. Backcountry travelers were surprised when they triggered avalanches on similar layers in the West North zone, and East North zone last weekend. 

    You probably won't get whumphing collapses, or shooting cracks to warn you. If you do see experience these signs, heed what the snow is telling you and stick to slopes less than 35 degrees. Digging and doing snowpack tests are one of the better ways to evaluate this type of instability. Cornices could also fail and trigger large persistent slabs. Use normal caution and avoid exposing more than one person to avalanche terrain at a time.

    A large snowmobile triggered avalanche that released on late January crust-facet layers. NE aspect at 5400' in the West North zone. 

    Photo: Graham Clark

Avalanche Discussion

Warm temperatures with clouds and breaks of sun are in the forecast. We're likely to experience a number of days with little to no refreeze of the upper snowpack starting Wednesday. Danger of wet loose avalanches may increase with this forecasted warm up, but there's uncertainty to how the snow may react. Rollerballs and loose wet avalanches (up to size D2) were reported on sunny slopes over the weekend. 

A week ago, signs of instability were plentiful. There are signs that the weak layer associated with the long dry spell in January is rounding and strengthening at low to mid-elevations. A recent observation from an east aspect at 6,000ft shows sudden collapse results in one test, and no results in another. Previous observers targeting it on northerly aspects have reported overall strengthening and decreasing likelihood of triggering avalanches. After a storm brought close to 2 feet of new snow early last week, observers reported shooting cracks and whumphing collapses on northerly aspects in the low 4,000ft elevation band (top of Stevens Pass, Yodelin, and Henry Creek clearcuts). 

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