Avalanche Forecast

Issued: Mar 12th, 2021 4:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada ldreier, Avalanche Canada

The storm is continuing strong with 20 to 30 cm new snow overnight and 30 to 50 cm during the day combined with extreme southwest wind. Travel in avalanche terrain is not recommended. 

Summary

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

FRIDAY NIGHT: Cloudy, 20 to 30 cm new snow and up to 60 cm in the very south of the region, 80 km/h southwest wind, alpine low -3 C, freezing level rising to 1000 m. 

SATURDAY: Cloudy, 30 to 50 cm new snow, 100 km/h southwest wind, alpine high 0 C, freezing level 1100 m.

SUNDAY: Mix of sun and cloud, 20 cm new snow, 30 km/h northwest wind, alpine high -5 C, freezing level 300 m.

MONDAY: Mix of sun and cloud, trace of snow, 30 km/h southwest wind, alpine high -3 C, freezing level 500 m.

Avalanche Summary

A natural avalanche cycle starting in the morning with avalanches up to size 2 was reported on Friday. 

Several natural glide snow avalanches and loose wet avalanches up to size 2 were reported on Wednesday. Some avalanche activity was observed on southerly aspects on Tuesday during the heat of the day. A few cornices were also triggered, which did not trigger slabs on the slopes below.

Snowpack Summary

Up to 60+ cm of new snow fell on Friday. And the storm will bring even more snow overnight and on Saturday during the day combined with extreme southwest wind. The new snow may overly feathery surface hoar on northerly aspects and in sheltered terrain features around treeline or a melt-freeze crust on southerly aspects and below treeline.

Around 100 to 200 cm overlies a persistent weak layer buried in mid-February that may still be a concern in parts of the region. The layer consists of feathery surface hoar crystals in areas sheltered from the wind and sugary faceted grains that formed during February's cold snap. Avalanche activity on this layer has mostly occurred west of Terrace along Highway 16 in the past week, but the layer could still be of concern anywhere it exists.

There are currently no layers of concern in the mid and lower snowpack.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Storm Slabs

An icon showing Storm Slabs

Friday's storm brought 60+ cm new snow, especially in the southern part of the region. The storm will bring 20 to 30 cm new snow overnight and another 30 to 50 cm during the day on Saturday combined with extreme southwest wind. The new snow will be touchy, especially where it sits on surface hoar on northerly aspects and in sheltered terrain features around treeline or a melt-freeze crust on southerly aspects and below treeline.

The extreme wind will distribute the new snow and may form wind slabs farther down slopes than expected. The wind will contribute to cornice growth and the additional load might lead to cornice failures.

In addition, the freezing level is forecast to rise to 1000 m during the night. The ongoing storm might keep temperatures low. However, in areas with 0 C or warmer temperatures loose wet avalanches and cornice failures may be expected.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Almost Certain

Expected Size

2 - 3.5

Persistent Slabs

An icon showing Persistent Slabs

Around 100 to 200 cm of snow may overly a persistent weak layer buried in mid-February. The likelihood of triggering the layer increases as the storm rapidly loads it.

Failing cornices may trigger avalanches on this layer on the slopes below and create very large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3.5

Valid until: Mar 13th, 2021 4:00PM