Avalanche Forecast
Issued: Dec 13th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
bchristie,
Avalanche Canada
Choose simple terrain that is sheltered from the wind. The storms keep stacking up, and a rider's weight may push a storm slab to a tipping point.
Summary
Confidence
Weather Forecast
Tonight's storm may bring more snow than originally anticipated. Cloudy weather and moderate snowfall continue, while the winds will ease off a little.
MONDAY NIGHT: Overcast. 10-20 cm of snow expected. Light to moderate southeast wind, trending towards strong or extreme south at higher elevations. Freezing level around 500m.
TUESDAY: Mostly cloudy. 2-12 cm of snow expected. Light southwest wind, trending to moderate at higher elevations. Freezing level rising to around 900m.
WEDNESDAY: Mostly cloudy. 0-2 cm of snow expected. Light southwest wind trending to strong westerly at higher elevations. Warming through the day, alpine temps around -11 C.
THURSDAY: Partial clearing overnight. Mostly cloudy through the day. 1-3 cm of snow expected. Light winds, trending towards moderate southwest, with strong westerlies in the alpine.
Avalanche Summary
Expect storm slabs to remain reactive to riders. Snowfall continues, and the snowpack still needs time to adjust to the new load.
This MIN report has details of a natural size 2.5 avalanche in an East facing treeline feature.
Reports from Saturday and Sunday indicate that the storm slab was touchy. Avalanche control with explosives produced many avalanches size 1.5-2, with one size 2.5 reported.
On Saturday, there was a report of avalanches being remotely triggered by skiers in the backcountry.
Another backcountry rider reported whumpfing and shooting cracks in 30-60cm deep slabs around treeline, causing their group to retreat to wind sheltered terrain.
Snowpack Summary
Snowfall from the previous storm is building new slabs on top of the old. There is a lot of snow available for wind transport, and winds are lighter, but still strong enough to encourage slab formation. Expect to find deeper and more reactive slabs in leeward slopes.
Below 2400m, expect to find a thick (20 cm or more) melt freeze crust on all aspects down 60-100 cm.
Several early season crusts are breaking down and forming a cohesive lower snowpack.
Snowpack depths range from 40-130 cm at treeline elevations. The snowpack tapers quickly below 1800m.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Storm Slabs
An avalanche that starts in the storm snow has the potential to step down to the Late November/Early December rain crust desribed in the Persistent Slab problem below.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
This 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
Valid until: Dec 14th, 2021 4:00PM
