Avalanche forecast

West Slopes South

Northwest Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

The southern half of the zone should be in the bulls-eye of this storm and dangerous avalanche conditions are expected to develop. Regardless of your location, look for actively blowing snow or fresh drifts to help identify wind-loaded slopes to avoid - they might be on a variety of aspects. If storm totals exceed expectations, you could see avalanche potential increase outside of wind-effected areas.

Avalanche problems

  • Wind Slabs

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

    Wind speeds should peak in the overnight hours on Thursday night before trending downward and switching direction during the day on Friday. This means you could encounter new Wind Slabs on a variety of aspects with potentially different reactivity based on their age or your location in the zone. Look for pillow-like drifts or areas that look “fat” compared to the surrounding terrain near ridgelines or on convex rollovers to help identify wind-loaded slopes to avoid. The wind also likes to sift snow into deeper piles in confined gullies or near the base of cliffs. In some locations, you could encounter firm snow that feels hollow or notice freshly built cornices to further help key you into potentially unstable areas to steer around.

    If the snow is really stacking up in your location, you could see slab development outside of wind-effected areas. Look for shooting cracks or blocks of snow failing easily on test slopes or in hand pits as an indication to start avoiding all steep slopes over 35 degrees.

    (3/5/2023)

    A human-triggered Wind Slab near 3-Way Peak in the Crystal Backcountry earlier this week. [N, 6500ft]

    Photo: Roger Strong

Avalanche Discussion

Thursday was a windy one around the West South, and in the southern half of the zone, it was fairly snowy as well. Mount St. Helens and Mt. Adams appear to be getting the bulk of this storm and should continue to be the snow benefactors overnight into Friday. Locations closer to the crest such as White Pass should also do well. It's in these areas where you’re more likely to find dangerous avalanche conditions on Friday, particularly early in the morning. That’s not to say you won’t encounter avalanches elsewhere. With moderate to strong winds and a good shot of snow, you could find unstable slopes regardless of your location.

Leading up to this stormy period, the snowpack around the West South was believed to be generally stable and right-side-up. Convective snow showers and periods of sun breaks impacted the zone throughout much of the past week. Most recent avalanches have been shallow Wind Slabs or Loose Dry slides in steep terrain. On slopes that see direct sunshine, you could find some thin sun crusts in the upper snowpack while more shaded slopes were observed to harbor weak surfaces earlier this week. 

Besides the new snow problems you’ll need to manage on Friday, the concern heading into this loading event is that those weak surfaces were buried by light convective showers and could now come to life. That’s what happened in the neighboring Mt. Hood zone on Wednesday as moderate snowfall occurred. So be on the lookout for avalanches breaking widely or spanning terrain features as an indication to dial back your travel plans. 

Regions covered