Avalanche Forecast

Issued: Mar 18th, 2018 5:29PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Continued observations of reactive surface hoar have renewed concern for slab avalanche danger in the north of the region, especially on the more committing objectives. Avalanche danger is generally LOW in the south of the region.

Summary

Confidence

High -

Weather Forecast

Monday and Tuesday offer a drying trend for most of the province. A low approaching from the Gulf of Alaska may bring precipitation to the region beginning Wednesday night.MONDAY: Scattered cloud cover, freezing level beginning at 700 m rising to 1500 m, light variable wind, trace of precipitation possible. TUESDAY: Scattered cloud cover, freezing level beginning at 800 m rising to 1600 m, light west/southwest wind, no significant precipitation expected. WEDNESDAY: Scattered cloud cover, freezing level beginning at 700 m rising to 1600 m, light south/southwest wind, a few mm of precipitation possible in the afternoon.

Avalanche Summary

On Saturday two size 1.5 skier triggered avalanches were reported from steep northeast facing terrain at 2200 m.  The slabs were up to 20 cm in depth likely failing on the recently active surface hoar.We received a great MIN report on Saturday that details a size 3 skier triggered avalanche on the northwest face of Matier that likely occurred in the last few days.  More details here.  On Friday two size 2 slab avalanches were reported from a north/northeast facing feature between 2100 and 2400 m on the Duffey. The slabs were 20 to 40 cm in depth and failed on surface hoar up to 4 mm in size. Reports from Thursday included one observation of a small storm slab releasing with a ski cut on the steep flank of a couloir in the north of the region. Several other recent natural storm slab releases were observed in the same area, ranging from size 1-2 with crown fracture depths of 10 to 30 cm. North aspects were the most active.

Snowpack Summary

5 to 10 cm of new snow fell March 14th. In most areas the new snow buried a breakable crust formed by days of warm temperatures and sunshine. In the north of the region polar aspects (those that face north and east) are harboring cold snow and a tricky buried weak layer down 20 to 40 cm below the surface. The layer is widespread in the alpine and at treeline, but it is not everywhere. The layer is composed of surface hoar on polar aspects and a sun crust on solar aspects. This layer continues to produce human triggered avalanches on polar aspects on the Duffey and has not been reported in the south of the region.In the north of the region a weak layer buried mid-February is about 40 to 50 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. The snowpack is well settled in the south of the region around the Coquihalla and in Manning Park.Variable winds in the past month have created cornices on many alpine ridgelines. They become touchier as daily temperatures rise and with the strong late winter sun on clear days.

Problems

Storm Slabs

An icon showing Storm Slabs
Large storm slabs continue to be triggered by skiers in high elevation north and east facing terrain where old storm snow rests on reactive surface hoar. Loose wet avalanche hazard increases with daytime warming on south aspects and lower elevations. 
Carefully evaluate big/extreme terrain features before committing to them, its not full go time yet.Be very careful with open slopes and convex rolls, especially in more extreme terrain.Heads up! Cornices loom large and if they fail, they will likely initiate storm slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 19th, 2018 2:00PM