Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

We’re deep into a prolonged warm period without a significant overnight freeze. Warm temperatures, sunshine, and light winds should make for plenty of wet unstable snow. Pay particular attention to what’s above you. Natural wet avalanches may release from steep rocky faces with no warning. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Multi-day wet avalanche cycles are very challenging to predict. With yet another day of warm weather and sunshine, the scales could be tipping. Without the cooling winds, Saturday could shape up to be the most dangerous of this warm period. You’ll need to deal with two versions of the same problem. 

    It’s hard to say if you’ll see natural wet loose avalanches, but all the ingredients are there. You may not be able to assess them until it’s actively avalanching. Rocky slopes above you may warm much faster than where you’re standing. Choose routes that limit any time you spend under big faces especially where snow still clings to rocks or cornices overhang the slope. Cornices and snow shedding can be dangerous in their own right even before they trigger a wet loose avalanche. 

    The other flavor of this problem is much easier to anticipate. You will be able to push loose slides on steep slopes where you find wet sticky snow. A weak crust may limit this issue in the morning, but that won’t last long. While most of these slides should be small, if they catch you they might not let go, and could take you where ever they run.

    This may be a good day to be out of the mountains early, especially if you start to see even small wet loose slides. Don't forget about all that terrain you'll need to cross on your way back to the car. 

    (2/27/2025)

    A natural wet loose avalanche near Far Away Rock on Mt Rainier. Avalanches will be possible on steep and sunlit slopes on Friday. 

    Photo: Dallas Glass

Avalanche Discussion

Preliminary Report: On Friday, February 28, three snowmobilers were riding near Harts Pass in the East North zone when they triggered a large slab avalanche. Two riders were caught and carried. One rider was fully buried and killed. The other was partially buried and injured. NWAC is working with local avalanche professionals to conduct an investigation. Our deepest condolences to the family, friends, and community. (NE, 6,800ft HS-AM-D2.5-R4-O)

Middle elevation temperatures haven’t dipped below freezing since Wednesday across most of the zone. Even with such warm weather, clear skies Friday night should allow for a bit of surface cooling and result in a weak freeze in open areas. With another warm sunny day in store, it might feel more like May than March, and that shallow crust won’t last long. 

It’s hard to say with certainty that there will be significantly more natural wet avalanches on Saturday, but without any significant cooling wind, the odds seem to lean in that direction. With the prolonged warmth, slides might not only be more common but, they could also become larger. To make it even more complex, some parts of the zone could see the scales tip, while others see less activity. 

So far wet avalanches in the West South zone have been pretty limited. While there have been plenty of rollerballs, wet loose slides have been generally small. An NWAC forecaster near Crystal Mt on Friday found he could push snow late in the day on steep sunny slopes. 

Any avalanches should be limited to the recent snow (12-20 inches, 30-50cm) above the recent atmospheric river (AR) crust. This snow is generally very well settled, strong, and bonded to the crust. All those things should help. 

If you’re in search of dry snow, higher elevation, shaded terrain seems to have generally escaped the heat. However, most of these areas are wind affected. If your travels are taking you above our forecast area (~8000ft) on some of the volcanoes, significant blowing snow has been observed in these areas. While it’s still warm up high, you’ll likely encounter other types of avalanche concerns. 

Régions couvertes