Avalanche Forecast

Issued: Dec 25th, 2018 3:00PM

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.

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

Summary

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Cloudy with light snowfall, freezing level below valley bottom.WEDNESDAY: Cloudy with light snowfall, accumulation 5 cm, moderate southwest winds, alpine temperature -9 C, freezing level below valley bottom.THURSDAY: Mix of sun and cloud, light northwest winds, alpine temperature -7 C, freezing level below valley bottom.FRIDAY: Increasing clouds over the day, light to moderate southwest winds, alpine temperature -6 C, freezing level below valley bottom.

Avalanche Summary

No avalanches were observed in the region on Monday. 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

Wind slabs may linger in lee terrain features at high elevations. Otherwise, reports suggest that the recent snow is bonding well to the snowpack. Below around 1800 m, expect recent storm snow to sit on a melt-freeze crust. Although limited reports are available, recent MIN posts suggest that the snow is bonding relatively well to the crust.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. There has not been reports of avalanche activity on this layer for 5 days. Although this layer is likely gaining strength, field observations show that slab avalanches remain possible on this layer where it exists. 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. A very large trigger, such as a cornice fall, would likely be needed to form an avalanche on this layer.

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

Reports are limited, but wind slabs may linger at high elevations in the immediate lees of terrain features.

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, North West.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 26th, 2018 2:00PM