Avalanche Forecast

Issued: Dec 23rd, 2018 4:10PM

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

mconlan, Avalanche Canada

South Coast Inland.

Wind slabs may linger at higher elevations. For the north of the region, be diligent around treeline, where a buried weak layer still lingers. See the forecaster's blog, which describes this persistent problem: www.avalanche.ca/blogs/persistent-slab

Summary

Confidence

Moderate - Due to the number of field observations.

Weather Forecast

SUNDAY NIGHT: Mostly cloudy, freezing level 1000 m. MONDAY: Clearing over the day, light south winds, alpine temperature -8Â°c, freezing level 900 m. TUESDAY: A mix of sun and cloud, light northwest winds, alpine temperature -9Â°c, freezing level below valley bottom. WEDNESDAY: Mostly cloudy, light southwest winds, alpine temperature -9Â°c, freezing level below valley bottom.

Avalanche Summary

No avalanches were observed in the region on Saturday. The last large cycle was on Thursday in the north of the region, with large avalanches up to size 3. These avalanches ran within the storm snow as well as on the weak layer described in the snowpack summary.

Snowpack Summary

Around 10 cm of snow fell in the region on Sunday with associated strong winds, likely forming small wind slabs in the immediate lees of ridges. Below around 1800 m, expect the storm snow to sit on melt-freeze crust formed by rain from Thursday's storm. In the north portion of the region and possibly the far south, a weak layer of facets and surface hoar lies below all this storm snow, around 100 to 150 cm deep. The weak layer appears most prominent around treeline, up to 2000 m. While the layer is likely gaining strength, field observations show that slab avalanches remain possible on this layer where it exists. See this MIN post for snowpack test results around the Duffey on this layer. Near the base of the snowpack, a crust exists with weak and sugary facets beneath it. This could potentially still be of concern in high north-facing aspects where the snowpack rests on very smooth ground cover.

Problems

Persistent Slabs

A weak layer buried 100 to 150 cm has the potential to produce large avalanches. This layer is likely most problematic in the north of the region and possibly the far south, around treeline and lower alpine elevations.

Cornices are large and looming, and could trigger persistent slabs on slopes below.Use conservative route selection and choose moderate-angled slopes with low consequence.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Expect to find wind slabs in the immediate lees of terrain features. They may take a couple of days to bond to underlying surfaces.

Use ridges or ribs to avoid pockets of wind-loaded snow.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 24th, 2018 2:00PM