Bulletin d’avalanche

North Rockies

Feb 13 – 14, 2022Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Tue
Wed
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible

Points saillants

A widespread surface crust will create safe avalanche conditions but poor riding quality.

If this crust breaks down at lower elevations loose wet avalanches will be possible in steep terrain.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    1–2

    This is only a concern in the southern part of the region. If the snow surface remains dry in the high alpine, strong westerly winds may have redistributed available snow into wind slabs in lee areas. Be aware as you transition above the rain crust and avoid any wind-loaded areas.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    1–2

    Warm temperatures and light rain may cause the surface crust to break down throughout the day. If the crust does break down, loose wet avalanches will be possible in steeper terrain

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

The ridge of high pressure will start to break down with increasing cloud cover and the potential for light precipitation.

Saturday Overnight: Mainly cloudy with the potential for light precipitation. Freezing level dropping to around 500 m. Moderate northwest winds at ridgetop.

Sunday: Mainly cloudy with light precipitation. Freezing level rising to around 1500 m in the afternoon. Light southwest winds at ridgetop.

Monday: Cloudy with snowfall. Freezing level around 1000 m. Light to moderate southwest winds at ridgetop.

Tuesday: Mainly cloudy with light snowfall. Freezing level around 500 m. Strong to extreme northwest winds at ridgetop. 

Avalanche Summary

During the rain event on Wednesday, a natural avalanche cycle occurred. Numerous wet loose avalanches were observed on all aspects and elevations. A few notable large slab avalanches were observed in the south of the region, which we suspect occurred during this rain event. Examples of these avalanches can be seen in this MIN report. 

The last persistent avalanches associated with the late January surface hoar layer occurred on February 7th in the south of the region. These natural avalanches occurred on a shaded aspect below treeline.

Snowpack Summary

Recent rain and high freezing levels created a widespread curst on the snow surface of variable thickness that extends all the way to mountain top. Where this crust is thick and supportive, avalanches are unlikely. Warm temperatures, rain or strong solar radiation could cause this crust to break down.

Below the crust, last week's 30-50 cm of storm snow buried a weak layer of surface hoar crystals. The last reported avalanche on this layer was on February 7th in the southeast of the region and it is becoming increasingly hard to find in the snowpack with no recent reactivity in tests. 

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • A crust on the surface will help bind the snow together, but may make for tough travel conditions.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • Watch for areas of hard wind slab on alpine features.

Régions couvertes