Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 7 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

How dry the snow is will determine what type of avalanche you’re dealing with. Avoid steep terrain where the snow is turning wet and heavy, or where you see rollerballs, pinwheels, or small wet avalanches. Long shooting cracks in drier snow are a clear red flag that slab avalanches are likely on steep slopes.

Problèmes avalancheux

  • Storm Slabs

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

    Moderate snowfall combined with rising temperatures sets the stage for storm slabs to develop over slightly softer, weaker snow below. Expect slab reactivity to increase through the day, with peak instability in the afternoon. If snowfall amounts exceed the forecast, expect greater danger at mid elevations as well.

    You’re most likely to trigger a slab on leeward slopes loaded with wind-drifted snow, or during periods of heavier snowfall. Use small test slopes and hand pits to assess how new and wind-drifted snow layers are bonding. Stomping on wind-drifted features, such as small cornices or wind lips, can also help you evaluate wind-loaded slopes.

    Use small, wind-drffted features for slope tests.

    Photo: Jason Speer - Baker Mountain Guides

  • Loose Wet

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

    Rising snow levels will likely lead to an uptick in wet avalanche activity, especially where fresh snowfall is followed by warming temperatures or rain. Wet avalanches are most common below steep rocky headwalls and cliffs, but could also be triggered on any steep slope. If temperatures run warmer than forecast, wet avalanche activity may also extend into higher elevations. Low elevations should see few avalanches, as nearly no snow has accumulated there in the last five days.

    Pinwheels are a sign the snow  surface is warming up.

    Photo: Zack McGill - Cascade Mountain Ascents

Avalanche Discussion

Dank, plaster-like snow was the story on Sunday, with about 5 inches of moist new snow observed at 5,000 feet. The new snow layers were generally well-bonded, though the wet snow produced plenty of rollerballs and pinwheels on steeper slopes. A bit of sluffing was reported where new snow was poorly bonded to crust. A few crowns from slightly older D1 slab avalanches were observed on northerly, wind-loaded slopes around 4,700 feet in the Baker Backcountry. 

On Saturday, small natural wet avalanches were seen in Canyon Creek and also on Shuksan Arm. A cornice failure that triggered a wet avalanche, D2 in size, occurred on the north side of Table Mountain above Iceberg Lake. Several older cornice failures were also noted in the same area.

At mid elevations, the new snow was generally too moist to support much wind transport or slab formation. Conditions are likely different at upper elevations, where stronger winds and colder, drier snow prevailed. Poor weather and limited visibility kept most travelers out of the alpine, leaving no observations from higher terrain.

Looking ahead, temperatures are forecast to continue climbing with freezing levels reaching 9,000 feet or higher by Tuesday afternoon. Periods of full sun are also expected. While not a certainty, there is a good chance of larger and longer-running wet avalanches, especially at upper elevations that have received several feet of new snow over the past five days.

Régions couvertes