Avalanche Forecast

Archived

Apr 21st, 2023–Apr 22nd, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

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 or hard, smooth layers.

Confidence

Moderate

Avalanche Summary

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.

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 60 cm of snow since last weekend, with light snow continuing through Saturday afternoon. The wind was strong to extreme from the southeast to southwest up until Friday morning. This means that thicker deposits may be found in lee terrain features in wind-exposed terrain.

This recent 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

Friday Night

Cloudy. Trace of snow expected. Freezing level falling to 1000 m. Treeline temperature around -3°C. Light southwest ridgetop wind.

Saturday

Cloudy. 2 to 5 cm of snow expected. Snow/rain line between 500 and 800 m. Treeline high around 0 °C. Light southwest ridgetop wind, trending to moderate at very high elevations.

Sunday

Cloudy. 10 to 20 cm of snow expected overnight, and 3 to 10 cm through the day. Snow/rain line between 1000 and 1500 m. Moderate south or southwest ridgetop wind, trending to strong at high elevations.

Monday

Mix of sun and cloud. Light snowfall expected. Snow/rain line between 750 and 1500 m. Light variable ridgetop wind.

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.

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.