Avalanche Forecast

Issued: Dec 30th, 2013 8:59AM

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

jfloyer, Avalanche Canada

Purcells.

In general terms, the north of this region has higher avalanche danger compared with the south. Ratings reflect the danger in the north.

Summary

Confidence

Good

Weather Forecast

Tuesday: Dry, cloudy with some sunny breaks. Treeline temperature around -6C. Ridgetop winds aronud 40 km/h from the W or NW.Wednesday: Dry with some good sunny periods. Temperatures starting cold but rising to around -3C in the afternoon. Winds around 30 km/h from the NW.Thursday: Light precipitation becoming more steady later in the day. Temperatures rising in the afternoon to around -1C. SW winds up to 60 km/h.

Avalanche Summary

A size 3 natural avalanche was reported from the Bugaboos on Sunday on a NE aspect at 2650m, triggered by a cornice release that pulled out a large slab all the way to ground on the slope below. Smaller avalanches have been observed in response to ski cutting and recent loading from new snow and wind on both south and north aspects. Outside the boundary of this region to the north of Golden, there was an incident in the Hope Creek drainage, where four people were involved (with two sustaining injuries) in a size 3 avalanche in an alpine feature.

Snowpack Summary

Up to 25 cm of new snow from the past 5 days has been redistributed by moderate to strong northwest and southwest winds. These new windslabs cover older, stiff, dense wind slabs in exposed lee terrain at and above treeline. In the upper 80 cm of the snowpack a couple persistent weak layers exist, comprising of surface hoar and a facet/crust combo. This interface has produced variable results with snowpack tests, and operators are keeping a close eye on them as the load above increases and/or a slab develops.A bigger concern, especially in the Northern part of the region where the snowpack is thinner and more variable is weak faceted and depth hoar crystals combined with a crust from early October. This is now down around 80-120 cm. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on steep, convex, north-facing slopes.

Problems

Wind Slabs

Recent moderate and strong winds have created new wind slabs that have buried old ones on a variety of aspects. A small wind slab release may be enough to trigger a deep weak layer, producing a large and destructive avalanche.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

The most likely place to trigger a deeper layer is on a steep, convex, north-facing slope in an area with a relatively shallow snowpack.

Caution around convexities or areas with a thin or variable snowpack.>Use conservative route selection, stick to moderate angled terrain with low consequence.>Parking, eating lunch, and regrouping in runout zones is bad practice.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

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