Avalanche Forecast

Issued: Dec 5th, 2018 4:21PM

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

Sea To Sky.

Strong to extreme outflow winds showed up uninvited over Tuesday night. Look for recently formed slabs hiding out in atypical areas on Thursday.

Summary

Confidence

Moderate -

Weather Forecast

Wednesday night: Clear. Light northwest winds.Thursday: Sunny. Light east winds. Alpine high temperatures around -1 with an above freezing layer sitting at about 2000 metres. Cooler at lower elevations.Friday: Sunny in the morning, becoming cloudy over the day. Light south or southeast winds. Alpine high temperatures around -1, cooler at lower elevations with a mild temperature inversion breaking down over the day.Saturday: Cloudy with scattered flurries bringing 2-5 cm of new snow. Light south winds. Alpine high temperatures around -4 with freezing levels to 1000 metres.

Avalanche Summary

No new avalanches were reported over the past several days.Explosives control work in the Whistler area on 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 grown a widespread new layer of feathery surface hoar crystals on the snow surface. Recent sunshine has likely replaced this surface hoar with a new crust on steeper sun exposed aspects while recent strong upper elevation winds scoured it from most 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 20 cm at 1800-2000 metres, where it sits above a strong rain crust, to upwards of 30-40 cm in the alpine above 2000 metres, where the crust is not present. Here, the storm snow shows good signs of bonding well to the now well-settled mid snowpack.Above 2000 m, about 50-150 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 unexpected bout of strong to extreme northeast winds Tuesday night has formed thin new wind slabs in a 'reverse loading' pattern in alpine areas. This means new slabs can be expected to be scattered around southwest aspects.

Expect freshly wind loaded pockets of unstable snow in the lee of ridge crests and roll-overs.Analyze terrain for areas that have been reverse loaded by recent winds.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 1.5

Loose Wet

Warm temperatures and 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 that low angle December sun tends to target steeper slopes.