Avalanche Forecast

Issued: Dec 5th, 2018 4:54PM

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

cgarritty, Avalanche Canada

South Coast Inland.

Access to the alpine remains an unappealing prospect. Be ready to manage a mix of possible surface instabilities if you're planning a mission to where the snow is.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Wednesday night: Clear with some low level cloud due to an alpine temperature inversion. Light northwest winds. Thursday: A mix of sun and lingering low level cloud. Light northeast winds. Alpine high temperatures around -4. Cooler at lower elevations due to an alpine temperature inversion.Friday: Mainly sunny with cloud increasing over the day. Light south winds. Alpine high temperatures around -1, cooler at lower elevations due to the lingering temperature inversion.Saturday: Mainly cloudy with scattered flurries bringing a trace of new snow. Alpine high temperatures around -4 with the temperature inversion breaking down over the day.

Avalanche Summary

Two recent very large (size 3) avalanches were observed in the Joffre Lakes area on Saturday. These released from the high alpine northeast and northwest faces of Mt. Joffre and Mt. Matier, respectively. The evidence of the Mt. Matier slide features several 'step downs' as the slide progressively triggered deeper layers of the snowpack, all the way down to previous summer snow cover. Both slides likely released during last week's storm.Please submit any observations you have to the Mountain Information Network here.

Snowpack Summary

Days of cool, clear weather have grown a reportedly widespread new layer of feathery surface hoar crystals on the snow surface. Recent sunshine has likely replaced this surface hoar with a new sun crust on steeper sun exposed aspectsBeneath this surface, the cold temperatures have also been gradually transforming storm snow from last week into a layer of faceted (sugary) snow. This layer of storm snow increases in depth from about 5-10 cm at 1600-2000 metres, where it sits above a rain crust, to around 20-30 cm in the alpine above 2000 metres, where the crust may not be present. Here, the storm snow is suspected to be bonding well to a settled mid snowpack.Above 2000m, alpine snowpack depths are approaching 175 cm, although recent reports suggest about half these depths around treeline in the south of the region. A crust/facet interface can be found near the ground in the alpine, but this may again be most prevalent in the north of the region. Although we have few observations of reactivity at this layer, it was a failure plane in several very large avalanches during last week's storm. It is thought that there is insufficient snow for avalanches below 1500 m.

Problems

Wind Slabs

Recent reports of strong outflow winds suggest that thin new wind slabs are likely to exist in 'reverse loaded' pockets on southwest aspects.

Analyze terrain for areas that have been reverse loaded by winds.Look for recently wind loaded pockets near ridge crests and roll-overs.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 1.5

Loose Wet

Strong sunshine may destabillize surface snow and promote loose wet avalanche activity on sun-exposed slopes on Thursday. Loose wet slides may occur naturally or with a human trigger.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Be aware of low angle December sun targeting its radiation on steeper slopes.