Avalanche Forecast

Issued: Jan 18th, 2015 8:33AM

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

jlammers, Avalanche Canada

South Columbia.

Large avalanches were running naturally on Sunday in alpine terrain. Continued triggering is a very real concern. For more discussion on the current conditions, check out this blog post: http://www.avalanche.ca/blogs/VLsBsCgAACYAJdfM/mid-jan-sh

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Unsettled conditions and light flurries are expected on Monday as a pacific frontal system exits the region to the southeast. By Tuesday a weak dry ridge of high pressure will rebuild. Confidence in the forecast for Wednesday gets shaky on Wednesday as weather models disagree on the ridge's ability to deflect a system creeping in from the northwest. Stay tuned! On Monday, ridgetop winds are expected to be moderate from the west, dropping to light from the northwest on Tuesday and Wednesday. Freezing levels should hover around 1400m on Monday, and then drop to near valley bottom for Tuesday and Wednesday.

Avalanche Summary

Natural and human-triggered storm slab activity to size 2 was observed over the weekend in response to new snow and wind, while loose dry avalanche activity was noted in steep, sheltered terrain. Additionally, explosives control in the region triggered size 2 cornice failures. It's important to remember, an avalanche in motion may also "step down" to a deeper, more destructive weak layer which formed in December.

Snowpack Summary

Up to 35cm of new snow has buried widespread 10-30mm surface hoar and a sun crust on steep sun exposed slopes. In higher elevation terrain, strong winds have shifted the new accumulations into reactive storm slabs. The problematic mid-December surface hoar/crust layer is typically down 80-120cm below the surface, and may still be sensitive to human triggering. The reactivity of this persistent weak layer appears to be quite variable but still has the potential for large, destructive avalanches in some areas. The layer appears to be the most reactive in the south of the region at and below treeline. In these locations the surface hoar is more likely to sit directly above a hard crust.

Problems

Storm Slabs

New snow and wind from Sunday has added size and reactivity to a developing storm slab. The new snow is expected to be especially reactive due to underlying weak crystals. In sheltered terrain, expect loose dry avalanche activity.

The new snow will require several days to settle and stabilize.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be cautious as you transition into wind affected terrain.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

Although less likely to trigger, persistent weak layers are capable of producing large and destructive avalanches. Use increased caution around big, unsupported slopes, especially in the south of the region.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Jan 19th, 2015 2:00PM