Avalanche Forecast

Issued: Mar 24th, 2018 3:35PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada jmcbride, Avalanche Canada

In the northern part of the region watch for wind slab development at upper elevations. A buried surface hoar layer may also still be reactive in these areas. Meanwhile in the south, generally safe avalanche conditions are present at all elevations.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY: Increasing cloud in afternoon. Ridge wind moderate to strong, southwest. Alpine temperature near -8. Freezing level 1000 m.MONDAY: Cloudy, flurries. Accumulation 2-5 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1500 m.TUESDAY: Cloudy, flurries. Accumulation 2-6 cm. Ridge wind strong, west. Alpine temperature near -2. Freezing level 1800 m.

Avalanche Summary

On Friday there were reports of isolated natural and skier triggered storm slab avalanches (size 1-1.5) from 15 to 25 deep on wind-affected convex and ridge top features in the alpine.Thursday there were reports of skier triggered size 1-1.5 wind slabs 10-30 cm deep on leeward, north-facing slopes at ridge top as well as sloughing below 1700 m in steep terrain.Last weekend, on Sunday a skier triggered avalanche was reported from around the Duffey on a north/northeast facing feature between 1900 and 2000 m. The size 2 avalanche failed on the March 8th surface hoar with a crown depth of 20 cm. And on Saturday two size 1.5 skier triggered avalanches were reported from steep northeast facing terrain at 2200 m on the Duffey. The slabs were up to 20 cm in depth, failing on the March 8th surface hoar.

Snowpack Summary

Thursday and Friday's storm snow (10- 20 cm) is sitting on a slippery crust that is present at all elevations on solar aspects. Low elevation polar aspects also have a crust, but treeline and alpine elevations feature a mix of large surface hoar and surface facets.In the north of the region, polar aspects (those that face north and east) are harboring cold snow and a surface hoar interface buried early March that is about 30 cm below the surface. This layer exists at alpine and treeline elevations, but it is not everywhere. This layer has recently produced large human triggered avalanches in the north of the region but has not been reactive in the south of the region. Also in the north of the region a weak layer buried mid-February is about 40 to 80 cm below the surface and has been reactive in snowpack tests. The layer is composed of sugary facets, a sun crust on solar aspects, and surface hoar that is present at and below treeline. In the south of the region, around the Coquihalla and in Manning Park, the recent storm snow overlies a recent crust that caps a well settled snowpack.

Problems

Wind Slabs

An icon showing Wind Slabs
Moderate to strong southerly wind combined with recent snowfall has formed new slabs at upper elevations particularly in northern parts of the region. These slabs overlie the old surface of crusts and surface hoar.
Be cautious as you transition into wind affected terrain.Minimize exposure to steep, sun exposed slopes if solar radiation becomes strong.If triggered wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 25th, 2018 2:00PM