Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger will be greatest on sun exposed slopes that become unstable with warming. Move off and away from steep terrain if the snow surface becomes saturated and unsupportable. Limited observations above treeline will require you to assess conditions as you ascend.

Avalanche problems

  • Loose Wet

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

    Natural and human triggered loose wet avalanches are likely in sun exposed terrain. Layers of drier new snow at the surface near and above treeline will be more susceptible to warming than rain saturated snow at lower elevations. Move to shaded terrain if you are sinking into wet, unconsolidated snow or witness signs of instability like rollerballs or recent avalanche activity. Plan on limiting travel directly under steep south facing terrain in the afternoon. Loose wet avalanches are unlikely if the snow surface is frozen or partially melted.  Be wary of cornices and other overhead hazards more likely to fall down with rapid warming.

    Wet loose avalanche on a west aspect near Lake Ann at 4800' in mid-February

     

  • Storm Slabs

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

    The 6-12” of precipitation that came down as rain at most elevations fell as many feet of dry snow up in the alpine. In addition, slightly lower snow levels the last few days produced up to 1’ of drier new snow at treeline. The likelihood of triggering a slab avalanche in new snow layers is decreasing but should still factor into your tour plan. Anticipate higher danger on wind loaded or sun warmed slopes. With no observations from alpine terrain it is up to you assess stability as you gain elevation. Mitigate uncertainty by using lower angle and planar terrain to bypass steep, unsupported features where you would be more likely to trigger an avalanche.

Avalanche Discussion

Periods of visibility allowed observers to document extensive avalanche activity from earlier in the week. Crowns showing wide propagation and step-downs in bed surfaces show that avalanche activity was not confined to new snow layers but also broke into deeper layers around the February 14th crust. Continued avalanche activity associated with rain and wet, unconsolidated snow conditions tapered off today with slightly cooler temperatures and diminishing precipitation. A few loose wet avalanches to D1 were observed during sun breaks on solar aspects and mostly involved only the top layer of new snow. No new avalanches were observed in older wet snow layers on test slopes or other steep features.

A few inches of drier new snow accumulated at lower elevations with up to 1’ at treeline by Thursday. The snowpack below the newest snow is rain affected down to the crust buried on February 14th. No notable weak layers were found and cool and clear nights combined with warm days in the forecast should gradually consolidate wet snow layers into a single, solid layer. Below treeline areas accumulated little snow and lost more snowpack to rain and warm temperatures in the last week.

Regions covered