Avalanche Forecast

Issued: Dec 21st, 2014 8:00AM

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

ali haeri, Parks Canada

Glacier.

Conditions have shifted towards a period of more conservative decision making in the backcountry. The latest surface hoar layer to be buried is the largest yet and will be most reactive as the slab overtop continues to build strength.

Summary

Weather Forecast

Snow easing off this morning, flurries forecast for the rest of the day with mild temperatures and mountain top winds northwest 30-50km/h. Unsettled conditions will persist with light snow as a weak ridge of high pressure slowly builds until a Pacific system arrives Tuesday night.

Snowpack Summary

20-30cm of recent snow has buried large surface hoar which sits on a rain crust to 2100m and on settled snow above 2100m. Settlement and winds that have just started to ramp up are likely to make the slab more sensitive higher up. Mid-pack is well settled with Nov 9 crust/facet layer in the bottom 30cm.

Avalanche Summary

A backcountry report of a skier triggered size 1.5 avalanche,10-15m wide, 10-15cm deep, from Balu Pass, northeast aspect, at ~2000m on a convex roll just below the ridge. 6 size 2.0 natural slab avalanches observed yesterday east of the Rogers Pass summit in the highway corridor.

Confidence

Due to the number of field observations

Problems

Storm Slabs

A storm slab is developing, 25 to 30cm thick, at higher elevations and wind-exposed areas. These slabs will bond poorly to the surface hoar layer which it sits on. Avalanches on this layer may run farther than expected and easily entrain snow.

Use caution in lee areas in the alpine and treeline. Recent storm snow has formed touchy slabs.Avoid freshly wind loaded features.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Deep Persistent Slabs

The November crust weaknesses at the bottom of the snowpack are difficult to trigger, but if they fail the consequences will be very high.

Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Dec 22nd, 2014 8:00AM