Avalanche Forecast

Issued: Dec 27th, 2018 3:57PM

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

Avalanche Canada mconlan, Avalanche Canada

Light snowfall will begin on Friday with the start of the weekend's storm. At higher elevations, you may still be able to trigger recent storm snow.

Summary

Confidence

High -

Weather Forecast

THURSDAY NIGHT: Mostly cloudy, freezing level below valley bottom.FRIDAY: Cloudy with light snowfall, accumulation 5 cm, moderate west winds, alpine temperature -5 C, freezing level below valley bottom.SATURDAY: Cloudy with snowfall, accumulation 20 to 30 cm, strong southwest winds, alpine temperature -3 C, freezing level 1500 m.SUNDAY: Partly cloudy, light north winds, alpine temperature -9 C, freezing level 600 m.

Avalanche Summary

Soft storm slabs from Wednesday's storm snow were reactive to skier activity, producing non-destructive, small (size 1) avalanches. Otherwise, no new avalanches were observed.

Snowpack Summary

10 cm of low-density snow is poorly bonded to a weak layer of feathery surface hoar, reported to be widespread and 5 to 10 mm in size. Snow amounts will be deepest and touchiest in the lees of terrain features immediately adjacent to ridges.Below 1800 m, around 50 cm of storm snow may not be bonding well to an underlying crust (see here). In other areas, reports indicate that the snow is bonding well to the crust.A weak layer of sugary facets and surface hoar lies around 150 to 200 cm deep in the snowpack. There hasn't been reports of avalanches on this layer for over a week. That being said, this layer may still exist in isolated areas around treeline in some portions of the region.At the base of the snowpack, weak and sugary facets are found below an early-season melt-freeze crust. This weak layer has been the culprit for sporadic, very large avalanches in alpine terrain in the past few weeks. The avalanches have occurred in areas where the ground roughness is very smooth, for example glaciers, firn, and shale/rock slab slopes. An avalanche could be triggered in this layer with a very large trigger, such as a cornice fall.

Problems

Storm Slabs

An icon showing Storm Slabs
The top 10 to 15 cm of snow, which may be thicker in lee areas of terrain features, may need some time to bond to underlying surfaces. Deeper in the storm snow, around 50 cm of snow may not be bonding well to a crust that exists below 1800 m.
Observe for the bond of recent storm snow to underlying surfaces before entering avalanche terrain.Use caution in lee areas; thicker deposits are expected due to recent wind loading.Cornices are large and looming near ridges. Give them a wide berth.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

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

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