Bulletin d’avalanche

South Coast Inland

Apr 19 – 20, 2021Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Wet slab and wet loose avalanches have been reactive with the recent warm weather. Start and finish your day early to avoid exposure to sun-exposed avalanche terrain. 

Steer clear of cornices overhead and plan your egress route carefully. 

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–3

    Cornices are at their largest at this time of year, and become weaker with warm temperatures and solar radiation.

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3.5

    The likelihood of wet slab avalanches increases during prolonged periods of warm temperatures, as the heat penetrates deeper into the snowpack. In the neighboring Seat to sky Region multiple very large wet slab avalanches have been observed in the last couple of days. These avalanches are dense, destructive, and can run far, reaching otherwise snow-free valley bottoms.

    Wet loose avalanche activity can also be expected on sun-exposed slopes and below treeline. These avalanches are generally smaller than wet slabs but they can gather mass as they travel and reach low elevations.

Confidence

Moderate - Confidence is due to a stable weather pattern with little change expected. Uncertainty is due to the limited number of field observations.

Weather Forecast

Tuesday: Sunny with light wind. Alpine high temperature near +4 and freezing level 2500 m.

Wednesday: A mix of sun and cloud with light to moderate wind. Alpine high temperature near +6 and freezing level 2600 m.

Thursday: A mix of sun and cloud and light wind. Alpine temperatures near +4 and freezing levels 2200 m. 

Expect the Alpine temperatures in the South on the Coquihalla to be warmer (+10-12 degrees) by the afternoon) than North on the Duffy. 

Avalanche Summary

The few reports still trickling in confirm that widespread loose wet and cornice activity was still ongoing as of the weekend. The Coquihalla zone has also seen glide slabs up to size 3 and 2 wet slab avalanches up to size 2 on Sunday.

In the neighboring Sea to Sky region, multiple wet slab avalanches were observed over the weekend near Whistler, size 2-4. Many of these involved the full depth of the snowpack, running to the valley bottom. We suspect similar activity to have occurred in the Inland region as well.

Snowpack Summary

A slight dip in overnight freezing levels combined with radiant cooling has formed a melt-freeze crust from 1700-2200 m. At lower elevations the snowpack is isothermal. The crust will likely break down quickly with solar radiation and freezing levels through the roof. Steep north aspects above 2200 m and higher may still hold dry wintery snow.

Cornices are large and looming along ridgelines. Sun and warm temperatures will increase the chances of cornice failures, especially when temperatures remain above zero overnight.

Terrain and Travel

  • Avalanche hazard is expected to to increase througout the day, think carefully about your egress.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Keep in mind that wet avalanches can be destructive due to their high density.
  • Avoid lingering or regrouping in runout zones.

Régions couvertes