Avalanche Forecast

Archived

Jan 20th, 2020–Jan 21st, 2020

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast Inland.

Use caution on steep open slopes in the northern part of the region where triggering wind slab and deep persistent slab avalanches is a concern.

Confidence

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

Weather Forecast

MONDAY NIGHT: Light snow with up to 5 cm, moderate wind from the south, alpine temperatures around -3 C.

TUESDAY: 5-15 cm of snow, strong wind from the south, freezing level around 1200 m with alpine high temperatures around -3 C.

WEDNESDAY: Cloudy with isolated flurries, light to moderate wind from the southwest, alpine high temperatures around -3 C.

THURSDAY: 5-15 cm of snow, strong wind from the southwest, freezing level up to 1800 m with alpine high temperatures around -1 C.

Avalanche Summary

On Sunday, several small (size 1) slabs were triggered by riders in the northern part of the region while small wet loose avalanches were reported around the Coquihalla. Several larger (size 2-2.5) natural slab avalanches were reported a few days ago during a period of intense snowfall.

Snowpack Summary

Relatively continuous light snowfalls over the past few days have brought recent storm totals to 25-50 cm in the north of the region. This recent snow has been heavily wind-affected in exposed areas at all elevations. The south of the region has received less snow and with warm temperatures has moist and crusty surfaces.

90-150 cm of snow currently sits above a weak layer of surface hoar from Christmas that professionals are tracking in the north of the region. It may be found at treeline and below on shaded aspects in sheltered areas. A deep persistent weak layer remains a serious concern at the bottom of the snowpack in the northern half of the region (e.g., Duffey, Hurley). It's made up of sugary faceted grains and a hard melt-freeze crust. This layer is most likely to be triggered in thin, rocky features where it exists closer to triggering forces on the surface.

There are currently no concerns about deep weaknesses in the snowpack near Coquihalla summit and elsewhere in the south of the region.

Terrain and Travel

Avoid freshly wind loaded terrain features.
In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.