Avalanche Forecast
Issued: Dec 11th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
bchristie,
Avalanche Canada
Continue to choose mellow slopes protected from the wind.
Wind and new snow are building slabs that can be triggered by a rider. It is still uncertain how well this new snow is bonding to the snowpack.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Overcast. 5-15 cm of snow expected. Moderate southwest winds, possibly extreme on high peaks. Freezing levels between 1000 and 1500m, starting to drop around midnight.
SUNDAY: Mostly cloudy. 5cm of snow expected. Moderate to strong southwest winds, isolated areas of extreme winds on high peaks. Freezing level 1000-1200m.
MONDAY: Partly cloudy. 0-5 cm of snow expected. Light southeast winds at treeline and strong southwest in the alpine. Alpine high around -4 C.
TUESDAY: Mostly cloudy. 7-15 cm of snow expected. Light to mod southwest winds. Alpine high around -8 C.
Avalanche Summary
No new avalanches observed. Expect human triggered avalanches to remain likely as the storm snow settles.
There are very few observations at this time, remember that a lack of avalanche observations does not necessarily mean there was a lack of avalanche activity.
Explosive control work earlier this week produced multiple wind slabs to size 1.5, running on the most recent melt freeze crust.
Snowpack Summary
Moderate to strong southwest winds continue to redistribute 15-25cm of recent storm snow, forming reactive slabs.
Snowpack depths are extremely variable. Before this storm, strong to extreme westerly winds stripped exposed terrain in the treeline and alpine, to the thick and smooth melt freeze crust (December 2nd) or to rock. In sheltered features, the wind has redistributed snow into wind loaded pockets of over 50cm.
Where the December 2nd crust does exist, facets may be forming on top, making this a layer to watch.
The snowpack holds several early season crusts about 20-40cm above the ground below 2300m. Last week's heavy rain saturated the snowpack and has begun to break down this crust at treeline and below, creating a cohesive lower snowpack.
Snowpack depths range from 30-110 cm at treeline elevations. The snowpack tapers quickly below 1900m.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Closely monitor how the new snow is bonding to the crust.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
Underneath the storm snow, there are lingering pockets of wind slab on an icy crust. An avalanche that starts in the storm snow has the potential to step down to these wind slabs, that were most prominent at treeline and in the alpine.
If you are unsure where the old wind slabs are lurking, then assume any storm slab avalanche that starts has the potential to get bigger than expected.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 12th, 2021 4:00PM
