Avalanche Forecast

Archived

Mar 13th, 2022–Mar 14th, 2022

Alpine

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast Inland.

Watch for pockets of fresh wind slab forming at upper elevations. Don't forget about a buried weak layer that remains triggerable.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Sunday night: Snowfall 3-8 cm, 30-50 km/h southwest wind, alpine temperature -4 C. Freezing level 1500 m.

Monday: Snowfall 5-10 cm, 30-40 km/h southwest wind, alpine temperature -2 C. Freezing level 1700 m.

Tuesday: Snowfall 5-10 cm, 20-40 km/h southwest wind, alpine temperature -3 C. Freezing level 1500m.

Wednesday: Overnight snowfall around 5 cm then cloudy, 10-20 km/h southwest wind, treeline temperature -6 C. Freezing level 1400 m.

Avalanche Summary

No new avalanche observations since Wednesday when a rider triggered a persistent slab avalanche along the Duffey at 2000 m on a northeast aspect. Another suspected persistent slab avalanche was triggered by a rider on Tuesday in the north of the region. Both slabs were around 30 to 40 cm thick, resulting in small avalanches (size 1 to 1.5). It remains possible that humans could trigger this layer, where it exists.

Snowpack Summary

Small amounts of new snow and southwest wind are likely forming wind slabs in lee terrain features. The new snow accumulates onto variable surfaces including a hard melt-freeze crust on solar aspects and low elevations, previously wind-affected snow at higher elevations and perhaps a thin layer of surface hoar or faceted snow in sheltered areas.

Around 30 to 60 cm deep, sugary faceted grains may be found around a melt-freeze crust that formed February in the north of the region (e.g., Duffey, Hurley). The layer has been most prevalent on north to northeast aspects around 1900 to 2100 m. Check out this forecaster blog for more info.

Various crusts may be found in the south of the region (e.g., Coquihalla, Manning) but reports suggest they are bonding to the snowpack and are not an avalanche concern.

There are no deeper concerns at this time.

Terrain and Travel

Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.