Avalanche Forecast
Issued: Dec 6th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
ahanna,
Avalanche Canada
Expect to see slab formation in recent snow due to increases in wind and temperature over the day Tuesday. Watch for signs of instability like shooting cracks or recent avalanches.
Summary
Confidence
Low - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
At a glance, we'll see a modest warm up on Tuesday, new snow arriving with strong wind overnight, then cooling down on Wednesday.
Monday night: Cloudy. Light southwest wind. Freezing level 500 m.
Tuesday: Flurries starting in the afternoon, accumulating up to 5 cm. Light to moderate southwest wind. Treeline high temperatures around -1. Freezing level rising to 1000 m.
Wednesday: Overnight snow 10-20 cm. Strong southwest wind. Treeline high temperatures around -7. Freezing level 500 m.
Thursday: Mostly cloudy. Light to moderate southwest wind. Treeline high temperatures around -7. Freezing level 500 m.
Avalanche Summary
On Monday, small loose dry and soft slab avalanches were observed naturally up to size 1 and up to size 1.5 with skier and explosive loads.
On Sunday, a skier accidentally triggered a size 1 wind slab near a convex northeast aspect in the Whistler sidecountry. A few small solar triggered point releases were also observed on steep south aspects.
On Saturday, some loose dry sluffing and thin soft slab reactivity were observed in steep terrain and near ridge crests. The slide in this excellent MIN from Garibaldi Park appears to have initiated out of extreme terrain, breaking up quickly and entraining low density surface snow.
Snowpack Summary
Tuesday's mild temperatures will promote settlement in the 10-15 cm of recent snow sitting over a layer of surface hoar crystals. This recent snow may be lightly wind affected near ridge crest in the alpine. Below 1700 m, the recent snow sits over a thick, supportive crust. Above this elevation up to about 2100 m, this crust still exists, shallowly buried by older, wind-pressed snow. Faceting has been observed on the underside of the crust with a moist midpack below.
Average snow depths at treeline are now likely closer to 150-200 cm, with a whopping 450+ cm above 1900 metres. Snowpack depths taper dramatically to below threshold very near the treeline/below treeline boundary.
Terrain and Travel
- Be alert to conditions that change with elevation.
- Wind slabs may be poorly bonded to the underlying crust.
- Keep in mind the crust offers an excellent bed surface for avalanches.
- Even a small avalanche can be harmful if it pushes you into an obstacle or a terrain trap.
Problems
Storm Slabs
As winds pick up late Tuesday and mild temperatures promote settlement in recent snow at lower elevations, we expect to see accelerated slab formation. Storm slabs may be surprisingly reactive where they sit on a weak layer of surface hoar or a slippery crust.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 7th, 2021 4:00PM
