Avalanche Forecast
Issued: Dec 12th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
bchristie,
Avalanche Canada
Choose smaller features, and avoid slopes that steepen as they descend. Adding a rider's weight to the recent storm snow may start a large avalanche that slides on a hard crust.
Summary
Confidence
Weather Forecast
Temperatures are generally dropping, and winds are easing, but spotty precipitation continues, with the possibility of waking up to a pleasant refresh on Tuesday morning.
SUNDAY NIGHT: Mostly cloudy. Possible trace of snow. Light southwest winds, strong at higher elevations. Freezing level at valley bottom.
MONDAY: Mix of sun and cloud. 2-5 cm of snow expected. Light southeast winds at treeline and strong south or southwest in the alpine. Freezing level rising to 500-1000m.
TUESDAY: Mostly cloudy. 5-10 cm of snow expected overnight, with another 0-5 cm through the day. Light to moderate southwest winds. Alpine low around -9 C.
WEDNESDAY: Possible clear morning, with increasing cloud over the day. Possible trace of snow. Light to moderate southwest winds, up to strong on higher peaks. Warming through the day, alpine high around -10.
Avalanche Summary
Reports indicated that the snowpack was quite touchy yesterday. Avalanche control with explosives and ski cuts produced several avalanches size 1 to 2, and one size 3. Most failed on top of the rain crust from the late November/early December rain events.
There are very few operations and backcountry users reporting at this time. Remember that a lack of avalanche observations does not necessarily mean there was a lack of avalanche activity.
Snowpack Summary
Moderate to strong southwest winds continue to redistribute 25-35cm of recent storm snow, forming reactive slabs. After the winds ease, these slabs will still need time to settle and become less reactive.
Check out this Mountain Information Network (MIN) post from our South Rockies Field team. It paints a great picture of the treeline snowpack north of Sparwood before it got 20-35 cm of new snow added on top.
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.
- Choose simple, low-angle, well supported terrain without convexities.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
This layer was very reactive yesterday in one location, but the crust is widespread across the province, and many operations have been watching it for signs of reactivity as the load on top of it increases. It may also get more reactive as cold temperatures promote faceting above the crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Recent moderate to strong southwesterly winds have formed recent storm snow into slabs that are deeper and more reactive in leeward features.
Aspects: North, North East, East, South East, North West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 13th, 2021 4:00PM
