Avalanche Forecast

Archived

Feb 26th, 2020–Feb 27th, 2020

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 possible, human triggered probable.

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.

Wind loaded pockets of snow may sit on a weak interface. Caution around wind loaded ridgetops in the alpine and on convexities at upper treeline elevations.

Confidence

Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack.

Weather Forecast

Wednesday night: Scattered flurries bringing a trace of new snow. Moderate southwest wind. Freezing level 1100 m.

Thursday: Scattered flurries bringing a trace of new snow. Moderate southwest wind. Freezing level 1400 m.

Friday: Mix of sun and cloud. Light to moderate southwest wind. Freezing level 1600 m in the north, 2000 m in the south.

Saturday: Around 5 cm new snow. Light to moderate southwest wind. Freezing level 1400 m.

Avalanche Summary

Some minor snowballing observed on steep sunny slopes Wednesday. A few skier controlled wind slabs up to size 1.5 were reported Tuesday. Natural and skier triggered wind slab avalanches were observed on northeast to west aspects in the alpine size 1.5-2 on Monday. We have not received reports of avalanche activity in the south of the region.

Snowpack Summary

15-30 cm of recent snow, and as high as 50 cm in the Coquihalla, may overly isolated patches of surface hoar in sheltered areas or sun crusts on solar aspects. Wind slab formation has been variable through the region. Extensive wind slab development has been reported in the western reaches of the region, and is suspected in the Coquihalla. In the northeast of the region, wind loading may be isolated to soft slabs in immediate lees in the alpine.

In the north part of the region (ie. Duffey/Hurley/Goldbridge), a deep instability exists at the base of the snowpack. It has not produced recent avalanche activity, with the most recent event on February 17. Rapid warming or heavy loading by new snow/wind/rain events

Terrain and Travel

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Brief periods of sun could quickly initiate natural avalanche activity.
Surface hoar distribution is highly variable. Avoid generalizing your observations.
Investigate the bond of the recent snow before committing to your line.

Problems

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.