Avalanche Forecast
Issued: Dec 10th, 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.
zryan,
Avalanche Canada
Continue to make conservative terrain choice while the storm snow stabilizes. There is still some concern for buried weak layers, which means that avalanches have the potential to pull back into lower angled terrain than you might expect.
Summary
Confidence
Weather Forecast
A fast moving pacific system brought heavy snow and wind to the region on Friday. A quieter weekend is in store, but we will continue to see convective flurries from the passing front.
Friday Overnight: The frontal system will pass over this evening, with easing wind and snowfall. Mainly cloudy skies overnight with strong to moderate southwest winds at ridgetop. Another 10-15 cm can be expected with freezing levels reaching valley bottom by morning. Alpine temperatures around -5 C.
Saturday: A mainly cloudy day with some continued snowfall as the low tracks south. 5-15 cm of accumulation can be expected accompanied by moderate to strong westerly winds at ridgetop. Freezing levels near valley bottom with alpine temperatures around -10 C.
Sunday: Partially cloudy with convective flurries, possibility for locally heavy accumulation ranging from 2-15 cm. Moderate south winds at ridgetop with alpine temperatures around -10 C.
Monday: A mix of sun and cloud with light southerly winds and isolated flurries, trace accumulation. Alpine temperatures around -15C.
Avalanche Summary
We suspect a natural avalanche cycle occurred during the storm on Friday.
On Thursday, highways NW of terrace had several explosive triggered loose dry and storm slab avalanches up to size 1.5. They also observed several natural loose dry and storm slab avalanches up to size 1.
Reports from recreation areas remain limited! If you do head into the backcountry, please share you observations to the Mountain Information Network!
Snowpack Summary
Across the region 40-80 cm of new snow has fallen in the past 2 days. In wind exposed areas, we can expect strong southwesterly winds to have created deep deposits of wind slab in lee features. In sheltered areas, this new snow will acts as a storm slab or loose dry problem.
There is still some concern for buried weak layers, will the possibility for buried surface hoar and faceting above the December 1st crust, now buried 40-120 cm deep. In the southern part of the region the December 1st crust has been reported up to 2000m, tapering to 500m in the northern reaches. The Terrace area has reported the crust to around 1200m.
Snowpack depths range from 150 cm- 300 cm at treeline and 200 cm- 400 cm in the alpine.
Terrain and Travel
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Problems
Storm Slabs
40-100 cm of new snow has fallen in the past two days, with another 10-15 cm to come throughout the day today. This amount of new snow has put significant new load on the snowpack and although snowfall is tapering, the snowpack will need time to adjust to this new load.
In wind exposed areas, strong southwest winds have created deep deposits of wind slab. In sheltered areas, the new snow will acts as a storm slab or loose dry problem.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
There is still some concern for buried weak layers, with the possibility for buried surface hoar and faceting above the December 1st crust. These layers where buried during the last storm cycle and will now be down 60-120 cm in sheltered areas.
The December 1st crust is present to around 1200m in the Terrace area, varying from 800m-1600m throughout the region. At treeline and below 5-10mm surface growth was observed prior to the last storm cycle. With limited visibility and observations in the past 3 days we are unsure if this surface hoar is preserved in any locations.
These weak layers will add heightened danger to an already significant amount of new snow. The presence of these weak layers mean that avalanches have the potential to pull back into low angled terrain, that we might otherwise consider 'safe' in higher danger.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 11th, 2021 4:00PM
