Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Saturday should be a bit of a “calm before the storm” where cloudy skies and a cool breeze create generally safe avalanche conditions. If you find yourself traveling on cold dry snow at upper elevations, keep an eye out for small pockets where the wind formed firmer pillow-like drifts. Don’t let one of these small slabs surprise you in high-consequence terrain.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1

    If you’re going to trigger an avalanche on Saturday, it will probably be in a small wind-loaded pocket. These slabs may be a few days old or they could be forming as the winds start to increase during the day. Either way, you want to pay attention for simple clues like textured surfaces, scoured slopes, and sharp drifts to anticipate where one of these slabs could exist. Even though they should be rather shallow and small, if you’re traveling above a cliff or in a rocky chute, one of these isolated slides could take you for a nasty ride.

    (4/13/2023) These wind slab clues helped us determine the local wind patterns and potentially wind-loaded slopes. Photo: Dallas Glass

Avalanche Discussion

After several days of spring-like weather, Saturday will be a bit of a transition for the mountains. Even though a weak storm will start to impact the zone, there shouldn’t be enough new snow to create any real avalanche issues. Instead, cloudy skies and a cooling breeze should help the snowpack remain strong and stable. 

We expect the snow surface to freeze, at least to some degree, Friday night. You could find a punchy crust or a firm solid surface on E-S-W aspects Saturday. This should limit any wet avalanche concerns. However, if the snow doesn’t freeze or there is more sunshine than expected, anticipate loose wet avalanches. You’re most likely to find wet mushy snow near rocks and on steep sunny slopes. If you encounter these conditions, use a bit of caution and seek our more frozen or shaded terrain. 

Observations from around the zone on Friday indicated that the sun was making quick work by weakening the snow surface. Rollerballs and a few small human-triggered loose wet slides were reported. In the Crystal backcountry, a rider trigger an avalanche on Threeway Peak where they were caught and carried over a cliff (N, 6500ft). Fortunately, they were uninjured. The observer made an excellent point, “Small slide but in consequential terrain made for a big event.”

One of the more interesting observations from Friday was of a very large (D3+) natural avalanche spotted south of White Pass in the Goat Rock Wilderness. A wide slab stepped down into older snow layers and produced a huge slide. We don’t know exactly when this avalanche occurred. It is a reminder, that even though the date on the calendar makes us think it’s spring, below thick surface crust (4/11), the snowpack is still very cold, dry, and layered. “Shed” style avalanches (glide, cornice, and deep slabs) will occur as the snowpack struggles to transition to spring. While these types of events are very unlikely Saturday, it’s just good practice to not hang out in the runouts of large avalanche paths particularly if you see looming cornices or crevasse-like glide cracks.

Expect variable travel conditions Saturday with breakable crust, icy surfaces, frozen debris, and cold dry snow. 

Régions couvertes