Avalanche Forecast

Issued: Jan 7th, 2019 4:27PM

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.

mconlan, Avalanche Canada

Purcells.

Recent strong winds have formed touchy wind slabs. Buried weak layers are also lingering and have recently released large, scary avalanches triggered by skiers. Conservative decision-making is recommended.

Summary

Confidence

High -

Weather Forecast

MONDAY NIGHT: Clearing, freezing level below valley bottomTUESDAY: Clear with afternoon clouds, light southwest winds, alpine temperature -11 C, freezing level below valley bottom.WEDNESDAY: Cloudy with light snowfall, accumulation trace to 5 cm, light to moderate southwest winds, alpine temperature -4 C, freezing level below valley bottom.THURSDAY: Cloudy with light snowfall, accumulation 5 cm, light to moderate southwest winds, alpine temperature -5 C, freezing level below valley bottom.

Avalanche Summary

A large (size 3) avalanche was triggered by a skier in the north of the region. It is likely that it released on weak faceted grains near the base of the snowpack, as described in the snowpack summary.On Sunday, one small (size 1.5) skier triggered avalanche was noted. It occurred in steep terrain above a cliff and the avalanche released to the ground, likely within the weak snow described in the snowpack summary. Otherwise, no new avalanches were observed on Sunday.These reports indicate that basal instabilities are still possible to trigger by humans.

Snowpack Summary

Wind slabs are reported as being widespread in lee and cross-loaded terrain features from recent south to west winds.There are deeper weaknesses in the snowpack. Professionals are still tracking a layer around 80 to 120 cm deep, composed of sugary faceted grains, feathery surface hoar, and a sun crust. The base of the snowpack may also still be composed of weak faceted grains. The likelihood of triggering these deep weak layers is low and would most likely be triggered by humans in areas where the snowpack is shallow.

Problems

Wind Slabs

Strong southwest winds have produced touchy wind slabs in lee and cross-loaded terrain features. Use caution when travelling through wind-affected terrain.

Avoid freshly wind-loaded terrain features.Cornices may be touchy; stay well-back on ridges and avoid travelling beneath them.If triggered, slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

Humans could trigger deeper weak layers in areas where the snowpack is shallow, such as near ridges and rocky terrain.

Best to avoid steep slopes and areas with a thin or variable snowpack.Be aware of the potential for full-depth avalanches due to weak layers at the base of the snowpack.Observe for signs of instability: whumpfing, hollow sounds, shooting cracks, and recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Jan 8th, 2019 2:00PM