Avalanche Forecast

Issued: Jan 8th, 2019 4:23PM

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.

You may still be able to find wind slabs at higher elevations. 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

TUESDAY NIGHT: Mostly cloudy with light snowfall in the west of the region, accumulation 5 cm, moderate to strong southwest winds, freezing level below valley bottom.WEDNESDAY: Cloudy with light snowfall, accumulation trace to 5 cm, moderate to strong 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 -4 C, freezing level rising to 1500 m.FRIDAY: Mostly cloudy, light southwest winds, alpine temperature -3 C, freezing level 1500 m.

Avalanche Summary

On Tuesday, a cornice fall triggered a persistent deep slab avalanche in the north of the region. The avalanche was very large (size 3.5) and released to ground, on a northerly aspect in alpine terrain.On Monday, 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, a small (size 1.5) skier-triggered avalanche was noted in the north of the region. 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.These reports indicate that basal instabilities are still possible to trigger by humans, particularly in the north of the region.

Snowpack Summary

Wind slabs are reported as being widespread in lee and cross-loaded terrain features at treeline and alpine elevations. Wind slabs may be found on all aspects due to variable wind directions.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. Humans could trigger these layers in areas where the snowpack is shallow.

Problems

Wind Slabs

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

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

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Jan 9th, 2019 2:00PM