Bulletin d’avalanche

Sea To Sky

Apr 22 – 23, 2023Avalanche Canada
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Archivé · expiré 3 years ago

Danger d’avalanche

Mon
Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Start on small slopes, and investigate how well the recent snow has bonded to the old surface before pushing into bigger terrain.

Slabs may take longer than usual to bond where they rest on weak layers or hard crusts.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2.5

    Moderate snowfall continues, building on existing storm slabs, which were typically failing around 30 to 60 cm deep earlier this week. Thicker and touchier slabs may be found in lee terrain features at high elevations. These slabs may take extra time to bond to the snowpack, particularly where they sit on surface hoar crystals or a smooth crust.

    Use extra caution around ridgecrests, rolls, and on convex slopes. Retreat to mellower terrain if you find signs of instability like shooting cracks, or recent avalanches.

Confidence

Low

Avalanche Summary

No notable avalanches were reported before 4pm on Saturday. Looking forward, we expect natural and human triggered storm slab avalanches to be likely on Sunday due to new snow and wind.

On Friday in the Whistler area, explosives avalanche control produced small (size 1 to 1.5) dry loose and storm slab avalanches. Through the day, solar warming caused numerous, small (size 1) wet loose avalanches.

On Thursday in the Brohm area, a large (size 2), rider triggered, storm slab avalanche was reported on a west aspect at treeline. It was 80 cm deep and it ran 300 m down the slope. See the Mountain Information Network post here for more information.

Avoiding cornice exposure is also a good idea, as they are very large and looming at this time of year.

Snowpack Summary

By the end of the day Sunday, storm snow totals will reach 15-30 cm in the alpine. At treeline and below, much of this recent precipitation fell as rain, so the surface is more likely to be wet or frozen.

The wind was strong to extreme from the southeast to southwest up until Friday morning, and is picking up again from the south or southwest on Sunday. This means that deeper, more reactive slabs may be found on leeward slopes in wind-exposed terrain that still holds dry snow.

Below the weekend's storm snow, up to 50 cm of settling snow from earlier in the week sits over a weak layer of surface hoar crystals on sheltered and shaded treeline and alpine slopes or a hard melt-freeze crust on sun-exposed slopes and on all aspects below 1500 m.

The remainder of the snowpack is well-bonded.

Cornices are large and looming at this time of year.

Weather Summary

Saturday Night

Cloudy. 5 to 10 cm of snow expected. Snow/rain line between 1000 and 1500 m. Treeline high around -1 °C. Light southwest ridgetop wind, trending to moderate at very high elevations.

Sunday

Cloudy. 2 to 5 cm through the day. Snow/rain line between 1000 and 1250 m. Moderate south or southwest ridgetop wind.

Monday

Mostly cloudy. Trace of snow/rain expected. Freezing level rising to 1600 m. Light variable ridgetop wind.

Tuesday

Low cloud. No new snow/rain expected. Freezing level rising to 1800 m. Light west or southwest ridgetop wind, trending to moderate northwest at high elevations.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Régions couvertes