Avalanche Forecast

Issued: Jan 1st, 2019 4:01PM

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

mconlan, Avalanche Canada

South Rockies.

The base of the snowpack is weak. It will remain likely for a while that humans can trigger deep persistent slabs.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TUESDAY NIGHT: Partly cloudy, moderate west winds, freezing level below valley bottom.WEDNESDAY: Mostly cloudy, moderate to strong west winds, alpine temperature -8 C, freezing level below valley bottom.THURSDAY: Cloudy with light snowfall, strong southwest winds, alpine temperature -3 C, freezing level rising to 1500 m.FRIDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, moderate to strong southwest winds, alpine temperature -5 C, freezing level 1500 m.

Avalanche Summary

No new avalanches were observed on Monday. Several loose dry avalanches and a few small (size 1) storm slab avalanches were triggered by skiers in this region on Sunday.

Snowpack Summary

Large variability in snow depths still exists in the region, ranging from practically no snow to almost 200 cm. For areas with sufficient snow, the upper snowpack consists of hard wind slabs on all aspects due to variable wind directions, a scoured and shallow snowpack on exposed southerly ridges, and generally soft snow in sheltered areas.Around 60 to 90 cm of snowfall in December has formed a slab that sits on a persistent weak layer of weak and sugary faceted snow that formed during dry and cold weather in early December. This layer is most likely to be triggered on steep features where snowpack depths are variable.The lower snowpack has a weak structure composed primarily of sugary faceted snow around a crust near the ground. Should a shallower avalanche be triggered, it is likely that it would step down and scour to the ground.

Problems

Deep Persistent Slabs

Around 60 to 90 cm of snow sits on a weak layer of sugary faceted snow. The snow beneath this is also weak and faceted, all the way to the ground. Avalanches triggered on this layer will likely scour to the ground, resulting in large avalanches.

Avoid steep slope angles or areas with a thin or variable snowpack.Be wary of slopes that did not previously avalanche.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Wind slabs may linger in wind-loaded terrain features at higher elevations.

Be cautious as you transition into wind affected terrain.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 2nd, 2019 2:00PM