Avalanche Forecast

Issued: Dec 26th, 2018 3:00PM

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

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Recent storm snow may need a bit longer to bond to the snowpack.

Summary

Confidence

High -

Weather Forecast

WEDNESDAY NIGHT: Clear skies, freezing level below valley bottom.THURSDAY: Sunny with afternoon clouds, moderate northwest winds, alpine temperature -8 C, 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 1700 m.

Avalanche Summary

Soft slabs from recent storm snow were reactive to skier activity on Tuesday, producing small (size 1) avalanches. Cornices were reactive to explosive control and some are separating from the ridge.

Snowpack Summary

Around 15 cm of new snow fell on a weak layer of feathery surface hoar, 5 to 10 mm in size. The new snow will likely not bond well to this layer, allowing for snow to move easily, fast, and far. Snow amounts will be deepest in the lees of terrain features immediately adjacent to ridges.Below 1800 m, storm snow from last weekend may not be bonding well to an underlying crust (see here). In other areas, reports indicate that the recent snow is bonding well.Another 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
Snow amounts of 10 to 15 cm from Wednesday, and possibly thicker in lee terrain features, may need some time to bond to underlying surfaces. Also, around 40 cm of storm snow from last weekend may not be bonding well to a crust below 1800 m.
Cornices are large and looming near ridges. Give them a wide berth.Use caution in lee areas; thicker deposits are expected due to recent wind loading.Observe for the bond of recent storm snow to underlying surfaces before entering avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 27th, 2018 2:00PM

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