Avalanche Forecast

Issued: Jan 30th, 2013 9:39AM

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

triley, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Overnight and Thursday: The Northwest flow is expected to continue to push the cold arctic air to the East. Northwest winds moderate overnight becoming strong during the day. No precipitation is expected tonight, and light snow falls of 3-5 cms are expected on Thursday. Alpine temperatures gradually warming on Thursday and freezing levels rising to about 1100 metres.Friday: No precipitation is expected as a high pressure system in the South influences most of the interior mountain ranges. Expect clear skies in the alpine and valley cloud. Freezing level at about 1100 metres.Saturday: High pressure should continue to influence. No precipitation expected, and freezing level at about 1100 metres.

Avalanche Summary

There was one skier accidental avalanche size 2.0 that released below treeline on a steep East facing roll, the slab was about 55 cms deep and released on a weak layer of surface hoar (probably Jan23rd). Natural sluffing from steep terrain up to size 1.5. Wind slab avalanches skier controlled up to size 1.5 on East aspects. A few natural slab avalanches releasing in the storm snow down about 60 cms.

Snowpack Summary

Approximately 40 to 60 cm of recent storm snow overlies a weak layer comprising of surface hoar in shady locations, facets at higher elevations and a sun crust on solar aspects. The recent new snow sitting above this interface has been slowly consolidating from fresh powder into a more cohesive slab. A mid-pack surface hoar layer buried in early January is down around 90 cm, and is best preserved below approximately 1700 m. A freezing rain crust has been reported near the surface (it may now be buried by light snow) in the Monashees, particularly in areas close to Mabel Lake.

Problems

Wind Slabs

Northwest winds are expected to develop wind slabs in the alpine and at treeline in the lee of terrain features. There is a lot of loose dry snow available for transport.

Avoid freshly wind loaded features.>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.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

40-60 cms of storm snow is sitting above a mix of hard old surfaces and areas of soft facetted snow. Some areas may have a weak layer between the old surface and the recent storm snow.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Jan 31st, 2013 2:00PM