Avalanche Forecast

Issued: Mar 22nd, 2018 6:30PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Strong southerly wind, continued precipitation and lowering freezing levels are expected to drive fresh storm slab development through Friday which may "wake up" buried surface hoar on north through east facing features at and above treeline.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

A rather complex weather pattern continues to deliver precipitation to the South Coast Inland. Lower freezing levels Thursday night and Friday should allow for snow at lower elevations. Precipitation is expected to diminish by Friday afternoon with some clearing in store Friday night and Saturday. THURSDAY NIGHT: Freezing level lowering from 1700 m down to valley bottom, strong to extreme south/southwest wind, 1 to 10 mm of precipitation. FRIDAY: Scattered cloud cover, freezing level starting at valley bottom rising to 1000 m, moderate to strong south/southwest wind, 1 to 2 mm of precipitation expected.SATURDAY: A few clouds, freezing level beginning at 400 m rising to 1200 m, light southwest wind, no significant precipitation expected. SUNDAY: Scattered cloud cover, freezing level beginning around 500 m rising to around 1100 m, moderate west wind, no significant precipitation expected.

Avalanche Summary

New snow and wind Thursday likely initiated natural avalanche activity that was probably most prevalent at upper elevations.On Sunday another 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. 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.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.

Snowpack Summary

Thursday and Friday's storm snow 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 tricky buried surface hoar interface down 20 to 50 cm below the surface. The layer is widespread in the alpine and at treeline, but it is not everywhere. This layer has recently produced large human triggered avalanches in the north of the region as detailed above. This layer 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 60 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.

Problems

Storm Slabs

An icon showing Storm Slabs
Strong southerly wind combined with ongoing snowfall is expected to form touchy storm slabs. Storm slabs in motion may initiate large avalanches failing on buried surface hoar 20 to 50 cm below the surface. Watch for wind slabs in unusual locations.
Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.Storm slabs are expected to be most sensitive to triggering in wind exposed terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Mar 23rd, 2018 2:00PM