Avalanche Forecast

Issued: Mar 21st, 2013 10:44AM

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

pgoddard, Avalanche Canada

South Coast.

Avalanche danger may spike on slopes receiving direct sun. Avoid travelling on or underneath sun-baked terrain.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Friday: Trace amounts of snow. Light N winds. Alpine temperature near -7.Saturday: No snow. Light winds. Alpine temperature near -6.Sunday: Light snow. Light winds. Alpine temperature near -8.

Avalanche Summary

On Wednesday, a widespread natural cycle was observed, with avalanches to size 2.5 failing with solar warming. Cornice fall was also occurring.A size 1.5 skier triggered slab avalanche was reported in the South Chilcotins on Tuesday. This avalanche occurred on a steep north aspect in the alpine and was triggered mid-slope. On Monday, a cornice fall triggered a size 3 slab avalanche on a NE aspect with a crown depth up to 100 cm. There is limited information on an accidentally triggered slab avalanche on Sunday in the Duffey Lake area that resulted in 2 people being buried.

Snowpack Summary

Recent snowfall amounts vary significantly throughout the region. In the Coquihalla area, around 25 cm of recent storm snow has been redistributed by strong winds over a crust, which is supportive to skis to at least 1700 m. A deeper melt-freeze crust was buried around a week ago by up to 90 cm of snow which is settling out. Further to the north (Duffey Lake), lighter amounts of new snow overlie a sun crust, wind slab, or settling storm snow. A buried surface hoar layer can be found down 50-70 cm and may be associated with a sun crust on southerly aspects at treeline. For all areas, expect extensive wind slabs and cornices in the alpine.

Problems

Wind Slabs

New wind slabs are likely in exposed lee terrain and cross-loaded gully features. A wind slab avalanche could trigger deeper instabilities lower down on the slope, creating a very large avalanche.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

A buried crust and/or surface hoar layer, now down 60-80 cm, could be triggered in sheltered areas near treeline. Avalanches stepping down to this layer could be very large and destructive.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 6

Cornices

Cornices are reported to be large and may become unstable with continued growth, mild temperatures and sunny periods.

Avoid steep slopes below cornices.>Stay well to the windward side of corniced ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 22nd, 2013 2:00PM