Avalanche Forecast

Issued: Dec 27th, 2018 4:05PM

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

mconlan, Avalanche Canada

South Coast Inland.

Snowfall will begin Friday as a storm approaches. For the north and far south of the region, be diligent around treeline, where a buried weak layer may still linger. See the forecaster's blog here, which describes this persistent problem.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY NIGHT: Partly cloudy, freezing level below valley bottom.FRIDAY: Cloudy with light snowfall, accumulation 5 cm, light to moderate west winds, alpine temperature -6 C, freezing level below valley bottom.SATURDAY: Cloudy with snowfall, accumulation 10 to 15 cm, strong southwest winds, alpine temperature -3 C, freezing level 1700 m.SUNDAY: Partly cloudy, light north winds, alpine temperature -9 C, freezing level 600 m.

Avalanche Summary

Reports are limited, but no avalanches were observed in the region on Wednesday. An interesting avalanche was reported in the MIN here, located east of the region near Penticton. The report shows photos of a large, remotely-triggered avalanche. Although the snowpack may be substantially different in this area, it appears that it may have released on one of the layers described in the snowpack summary, either the surface hoar/facet layer in the middle of the snowpack or the facets near the base of the snowpack.

Snowpack Summary

5 to 10 cm of low-density snow fell on Wednesday, covering what is reported to be a widespread weak layer of feathery surface hoar. Below this, about 30 cm of recent storm snow sits on a melt-freeze crust below around 1800 m. Reports are limited, but they suggest that the snow is bonding well to the crust. Expect the deepest deposits of storm snow to be in lee and cross-loaded terrain features.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 the past week. 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

Valid until: Dec 28th, 2018 2:00PM