Bulletin d’avalanche

Northwest Inland

Apr 25 – 26, 2023Avalanche Canada
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Archivé · expiré 3 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Forecast 10-20 cm of snow and strong southwesterly wind are expected to form wind slabs reactive to human triggers on lee features at treeline and above.

Concern for triggering large persistent slab avalanches remains. Avoid steep, rocky, and wind-affected areas where triggering slabs are more likely.

Problèmes avalancheux

  • Loose Wet

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

    Even short periods of strong solar radiation may trigger wet loose avalanches on steep, sunny slopes.

  • Wind Slabs

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

    Forecast 10-20 cm of snow and strong southwesterly wind are expected to form fresh wind slabs on lee features at treeline and above.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–3

    30-50 cm of snow sits above a layer of facets and surface hoar on shaded slopes. On other slopes, this layer is a crust with facets above. Whumfing and settlements in the upper snowpack have been reported on this interface as well as snowpack test results indicating that human-triggering this slab is possible. Avoid steep open slopes capable of producing large avalanches.

Confidence

Low

Avalanche Summary

Numerous naturally triggered wet loose avalanches up to size 2 were reported on all aspects/elevations on Monday.

Most professional operations are now closed which means we have very little snowpack or avalanche observation data. Please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.

Snowpack Summary

Forecast 10-20 cm of snow and strong southwesterly wind are expected to form fresh wind slabs on lee features at treeline and above.

A crust exists up to ridgetop on south-facing slopes and on all aspects up to approximately 1500 m.

A weak layer buried in late March is down 30-50 cm and exists as surface hoar or small facets on north facing slopes and a crust with small facets on top on sunny aspects. Test results show that this layer may be reactive to human triggers in isolated locations in the alpine where the layer is well-preserved. See MIN.

The middle of the snowpack is strong and contains numerous hard crusts. Near the ground, weak faceted crystals exist. There hasn't been avalanche activity on this layer recently, but it remains on our radar and may become active when we experience change, such as rapid loading (heavy snowfall or rain) or prolonged warming.

Weather Summary

Tuesday Night

Snow; 5-20 cm / 50 km/h south ridgetop wind / Temperature at treeline around -3 C / Freezing level 1000 m

Wednesday

Mix of sun and cloud with isolated flurries; 3-10 cm / 50 km/h southwest ridgetop wind / Temperature at treeline around 0 C / Freezing level 1300 m

Thursday

Mix of sun and cloud / 40 km/h southwest ridgetop wind / Temperature at treeline around 1 C / Freezing level 1400 m

Friday

Sunny / 10 km/h south ridgetop wind / Temperature at treeline around 8 C / Freezing level rapidly rising to 2700 m!

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

Régions couvertes