Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Unsettled, windy weather will approach on Monday with light snow in the mountains. If you hit the wrong spot, you could trigger a large and surprising slab avalanche on shaded, northerly aspects. Continue to keep your distance from large, steep slopes at mid and upper elevations.

Avalanche problems

  • Persistent Slabs

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

    Continue to use caution around avalanche terrain on the north half of the compass. There's still a chance that you could trigger a surprising slab avalanche that could break widely across a slope. Use extra caution on leeward sides of ridges that hold fresh drifts from northwest winds on Friday night. Watch for "red flag" signs like whumphing collapses, cracks shooting through the snow, and tests that propagate or fail suddenly. If you see these indicators, stick to slopes less than 35 degrees and avoid traveling in or under large avalanche paths and steep slopes. Put plenty of space between where you travel and big terrain features.  

    The late January weak layer can be found 1.5-2ft below the surface. Weak sugar-like facets (or surface hoar) sit above, and sometimes between, a crust. The weak layer is most consistent and well-developed on NW-NE aspects between 4,000ft and 4,700ft. This low elevation band produced startling collapses and shooting cracks last week. There is uncertainty with higher elevation, alpine terrain. Saturday was an active day in the West North zone, where backcountry travelers triggered large persistent slab avalanches on the same layer that exists in this zone.

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

    Photo: Graham Clark

Avalanche Discussion

Rollerballs and loose wet avalanches (up to size D2) have been reported on sunny slopes and at all elevations in the past 3 days. While wet avalanches aren't expected on Monday, watch for triggering them at low elevations. If you see significant rain or sun, especially in the eastern portion of the zone, you could encounter wet avalanches. Temperature inversions may cause some snow surfaces to be moist or weaker near 4,500-5,000ft.

While time and a lack of significant new snow are helping the late January weak layer, there is still some uncertainty whether travelers can trigger it. Observers targeting it on northerly aspects have reported variable results with some tests indicating the potential for triggering persistent slabs (Saturday, Skyline Ridge) and other tests and profiles indicating stability. There are signs that at mid-elevations the weak layer is rounding and strengthening but information is limited above 5,600ft.  On Thursday, explosive testing at Stevens Pass Mountain Resort produced no results on east through south aspects from 4,800 to 5,000ft. Early last week, observers reported shooting cracks or whumphing collapses on northerly aspects in the low 4,000ft elevation band (top of Stevens Pass, Yodelin, and Henry Creek clearcuts) after a storm brought close to 2 feet of new snow. Check out the other recent observations from Henry Creek, Upper Nason creek, and the Stevens Pass sidecountry. 

Regions covered