Avalanche Forecast

Archived

Mar 29th, 2021–Mar 30th, 2021

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, 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

Cariboos.

Storm slabs may remain reactive to human triggers as natural avalanche activity tapers off. Start with small terrain features, look for sign of instability and gather information before considering bigger terrain.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

Monday night: Scattered flurries. Moderate northwest wind. Freezing level valley bottom. Alpine temperature -13.

Tuesday: Scattered flurries. Moderate westerly wind. Freezing level 1400 m. Alpine temperature -7.

Wednesday: Sunny. Light to moderate southwest wind. Freezing level 1800 m. Alpine temperature -1.

Thursday: Flurries. Strong southwest wind. Freezing level 1700 m. Alpine temperature -3.

Avalanche Summary

We are still awaiting reports of avalanche activity from the weekend's storm. A widespread natural cycle is likely to have occurred Sunday.

On Saturday, evidence of an old size 2 cornice failure was observed at Allen Creek. Otherwise, we have no reports of avalanche activity since Wednesday's storm when there were a few reports of natural and human triggered storm slab avalanches.

Snowpack Summary

The weekend's storm dropped 20-50 cm of new snow over the region. This snow came with wind from southwest to northwest, loading thick slabs in lee features at upper elevations. The new snow is expected to bond reasonably well with underlying surfaces. Crusty and/or moist surfaces exist below treeline depending on elevation and time of day.

The new snow buries old stubborn slabs at upper elevations and a crust below treeline. Recent warm weather patterns are expected to have helped old persistent weak layers heal. The new snow load (and whether it triggers deeper slabs during the storm) may help shed some light on concerns over a facet layer 150 cm deep from the mid-February cold snap that resulted in few large cornice triggered avalanches in the first half of March.

Terrain and Travel

Keep in mind that human triggering potential persists as natural avalanching tapers off.
Start with conservative lines and watch for clues of instability.
Seek out sheltered terrain where new snow hasn't been wind-affected.
Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.