Avalanche Forecast
Issued: Dec 5th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
ghelgeson,
Avalanche Canada
The best travel plans for Monday will avoid convexities and sharp changes in terrain where it may still be possible to trigger old wind slabs. Take note of the current snow surface and let us know what you find, this is what all of Tuesday's storm snow will rest on.
Summary
Confidence
Weather Forecast
Status quo for Monday, but then it’s game on Tuesday as a potentially powerful storm sweeps into the area. Snow amounts are hard to pin down for Tuesday, but we could see as much as 50 cm of new snow. Stay tuned for more details as the storm gets a bit closer.
SUNDAY NIGHT: Temperature around -20 C, moderate to strong west/southwest wind, no significant snowfall expected.
MONDAY: Flurries, temperature around -20 C, moderate to strong southwest wind, 1 to 5 cm of snow expected during the day with another 1 to 5 cm likely Monday night.
TUESDAY: Snow, becoming heavy early Tuesday morning, potential for as much as 50 cm by Tuesday night, strong to extreme southwest wind.
WEDNESDAY: Broken cloud cover, daytime high temp around -10 C, light southwest wind, trace of snow possible.
Avalanche Summary
Some hardy Yukoners were out skiing Sunday and were kind enough to post a MIN of what looks to be a great day on snow despite the cold temps, more details here.
Avalanche control work on Saturday produced many large wind slab avalanches on NE facing features around 1700 m. Most of these avalanches stepped down to weak facets and rocks.
Lots of whumping and cracking have been reported across the region, a product of our shallow early-season snowpack which includes wind slabs and a weak facet/crust layer at the base of the snowpack.
On Tuesday, a size 2.5 skier-remote persistent slab was reported on the MIN (see report here). The avalanche was triggered from around 100m away, by a group of 5 riders on an east aspect at 1400m. The avalanche was suspected to have failed on an early-season facet/crust layer.
Snowpack Summary
Varied wind directions in the past week have created a mix of old and new wind slabs everywhere. Expect these wind slabs to be quite stiff in the current cold temps.
Snow depth at treeline is approximately 80-120 cm, depths in the alpine range from 100-200 cm.
A facet/crust layer can be found near the bottom of the snowpack. This layer was reactive to human triggering last week with a notable skier-remote avalanche on November 30th.
Terrain and Travel
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Be careful as you transition into wind affected terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Wind Slabs
Varied winds over the past week have created wind slabs almost everywhere, but they seem to be most reactive on northeast facing features. Cold temperatures over the past few days have decreased the likelihood of human triggering, but keep in mind that if triggered, wind slabs can step down to the late October crust, creating larger spooky avalanches.
Aspects: North, North East, East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A late October facet/crust layer near the base of the snowpack has shown reactivity in the past week. There is very little recent information about the sensitivity and distribution of this layer. The best bet for managing it is to stick to rather simple and well-supported terrain as you gather information.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 6th, 2021 4:00PM
