Avalanche Forecast

Archived

Apr 20th, 2023–Apr 21st, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Sea To Sky, Brandywine, Garibaldi, Homathko, Spearhead, Tantalus.

Evaluate terrain carefully and travel conservatively at higher elevations as the latest snow begins to stabilize. Slabs may take longer than typical to bond where they rest on weak or smooth layers.

Confidence

Moderate

Avalanche Summary

Small to large (size 1 to 2) storm and wind slab avalanches were triggered by riders, explosives, and naturally between Sunday and Wednesday, generally being about 30 cm thick but up to 80 cm thick in wind-loaded areas (as seen here) and primarily at alpine and treeline elevations. Some of the avalanches were triggered by small pieces of cornices failing.

The possibility remains of triggering storm and wind slabs in steep terrain features at treeline and alpine elevations or where this week's storm snow isn't bonding to surface hoar crystals or a smooth crust. Also note that cornices are very large and could fail at anytime.

Snowpack Summary

The region has seen around 50 cm of snow since the weekend, with another 5 to 15 cm expected Thursday night. The wind has been strong to extreme from the southeast to southwest during this time, including for Thursday night. This means that thicker deposits may be found in lee terrain features in wind-exposed terrain.

All this snow may sit on 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

Thursday Night

Cloudy with snowfall, accumulation 5 to 15 cm, 50 to 80 km/h southeast wind, treeline temperature -7 °C, freezing level 800 m.

Friday

Cloudy with light snowfall, accumulation 1 to 3 cm, 20 km/h southwest wind, treeline temperature -5 °C, freezing level 1300 m.

Saturday

Cloudy with snowfall, accumulation 2 to 5 cm, 20 to 40 km/h south wind, treeline temperature -1 °C, freezing level 1800 m.

Sunday

Cloudy with snowfall, accumulation 5 to 10 cm, 20 to 40 km/h south wind, treeline temperature -3 °C, freezing level 1600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Carefully monitor the bond between the new snow and old surface.
Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.