Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Stormy conditions are forecast to develop in the afternoon with heavy snowfall, strong winds and rising snow levels. Be ready to adjust your travel plans based on changing weather and snow conditions. Move towards sheltered, lower-angled terrain as conditions deteriorate.

Avalanche problems

  • Storm Slabs

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

    A warmer storm with heavy precipitation will impact the Cascades Monday afternoon into Tuesday morning. Precipitation is forecast to stay as snow at mid and upper elevations. There could be 8-12" of new snow by the end of the day.

    As usual, you are more likely to trigger a slab avalanche in wind-loaded terrain. But the combination of snowfall and rising temperatures is the setup to see unstable slabs in more sheltered areas as well. 

    Look for dense snow over a lighter, weaker layer below. Test slopes and hand pits should show if unstable slabs are forming. Long shooting cracks and avalanches are signs it’s time to avoid steep slopes. If you find less than 6” of new snow then slab avalanches are unlikely.

    Crown of natural storm slab avalanche from a prior winter. While this one was shallow, it propagated widely around the corner to the right.

  • Loose Wet

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

    Rising snow levels will trigger a changeover from snowfall to rain at lower elevations. While most of these areas don’t have the snow cover to produce avalanches, some do have enough. Look for wet avalanche activity at mid-elevations if snow levels are higher than forecast.

    Take note when precipitation switches to rain, especially if it’s falling on dry snow. Start looking for pinwheels and rollerballs as the surface becomes wet and mushy. Move off of and away from steep slopes if these signs of instability increase - or if you start seeing wet avalanches. 

     

    Wet, clumpy snow and rollerballs are signs you could find wet avalanches in steep terrain. 

    Photo: NWAC Public Obs

Avalanche Discussion

Strong winds with gusts to over 40mph were recorded at Pan Dome on Sunday. Observations were limited, but one person out Sunday found active wind transport and fresh slabs up to 8" deep. No shooting cracks, propagation, or triggered avalanches were reported.

On Saturday observers across West North found most wind-sheltered, mid-elevation terrain held about 6” of new snow with deeper drifts and wind slabs on leeward slopes. Bare crust was a common sight along scoured ridgelines and in high alpine terrain. Wind slabs were found to be unreactive despite the presence of a layer of softer snow between denser layers. The new snow was also well bonded to the old and wet - but now frozen - snow surface in wind-loaded areas.

A single natural avalanche, likely occurring during the latest storm on the 22nd, was observed on a north aspect at 5100’. No human-triggered avalanches were reported on Saturday despite sunny skies and lots of traffic.

Regions covered