Avalanche Forecast

Issued: Dec 6th, 2018 4:37PM

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

Avalanche Canada cgarritty, Avalanche Canada

Keep your eyes peeled for small, 'reverse loaded' wind slabs in the alpine.

Summary

Confidence

Moderate -

Weather Forecast

Thursday night: Mainly clear with light south winds.Friday: Mainly sunny with cloud increasing over the day and light flurries beginning in the evening. Light south winds climbing to moderate in the evening. Alpine high temperatures around -2, slightly cooler at lower elevations under a lingering mild temperature inversion.Saturday: Mainly cloudy with scattered flurries bringing a trace to 5 cm of new snow. Light south winds, increasing to strong southeast overnight. Alpine high temperatures around -4 with freezing levels near 900 metres.Sunday: Cloudy with flurries bringing approximately 5-15 cm of new snow. Strong south winds. Alpine temperatures decreasing from about 0 to -2 over the day as an above freezing layer at 2000 about metres (brought on by the warm storm) dissipates over the day.

Avalanche Summary

Solar warming and recent wind redistribution of surface snow allowed for small (size 1) loose snow and wind slab releases with ski cutting on solar aspects in the Whistler area on Wednesday and Thursday.Explosives control work in the Whistler area last Friday produced several size 1.5 cornice releases and one 20 cm deep size 1.5 storm slab. An outlier from explosives control work conducted last Wednesday was an explosives-triggered size 3 avalanche on a north facing alpine feature which stepped down to the early November crust.Please submit any observations you have to the Mountain Information Network here,

Snowpack Summary

Days of cool, clear weather have been growing a 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 aspects just as strong upper elevation winds scoured it from many alpine slopes. Below the surface, the recent cold has also been transforming last week's storm snow into a layer of faceted (sugary) snow. This layer of faceting storm snow increases in depth from about 15 cm at 1800-2000 metres, where it sits above a strong rain crust, to roughly 20-30 cm in the alpine above 2000 metres, where the crust is not present. Here, depending on exposure to recent outflow winds, the storm snow either shows good signs of bonding well to our well-settled mid snowpack or has been blown away entirely.Above 2000 m, about 100-200 cm of snow now sits on the early November melt-freeze crust. This crust may be layered with weak faceted crystals in places where it lies close to the ground. This is most likely to cause problems in glaciated terrain or on smoother, high elevation slopes where the summer snow did not melt out.

Problems

Wind Slabs

An icon showing Wind Slabs
An short bout of strong to extreme northeast winds Wednesday morning formed thin wind slabs in a 'reverse loading' pattern in alpine areas. These have likely stabilized for the most part but may remain reactive in more extreme terrain.
Analyze terrain for areas that have been reverse loaded by recent winds.Watch for wind loaded pockets of unstable snow in the lee of ridge crests and roll-overs.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 1.5

Valid until: Dec 7th, 2018 2:00PM

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