Avalanche Forecast
Issued: Dec 17th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Danger will increase throughout the day as wind and snowfall create fresh, reactive wind slabs. A buried persistent weak layer continues to be a concern, warranting careful assessment and wide terrain margins.
Summary
Confidence
Weather Forecast
Friday Overnight: Clear with a few cloudy periods in the evening, increasing cloud cover overnight. Light flurries possible in the early morning. Light to moderate northwest winds will shift southwest in the morning and increase into the strong range.
Saturday: Snowing through out the day, heavy at times, accumulation 10-25cm. Strong southwest winds at ridgetop. Freezing levels remaining near valley bottom with alpine temperatures rising from -12 C to around -7 C. Continued snowfall overnight, another 15-25cm of accumulation is possible.
Sunday: Partially cloudy with light flurries possible in the morning. Light west winds, alpine temperatures around -10C.
Monday: Partially cloudy in the morning, with increasing cloud cover in the afternoon with flurries. Light southwesterly winds increasing in the afternoon into the moderate range.
Avalanche Summary
On Friday, operators reported several size 2.5 natural and cornice triggered storm slab in the alpine. Numerous explosives' and ski cutting results both loose dry and storm slab where observed up to size 2. One explosive result reported failing down to the early December crust in an isolated area. One natural size 2 persistent slab was reported on a NE aspect in the alpine.
On Friday, several natural slab avalanches where reported in the backcountry adjacent to Fernie Alpine Resort, with one notable persistent slab failing on the early December crust.
Snowpack Summary
Since Monday, 50 cm of snow has accumulated, with another 10-20cm expected throughout the day today. Moderate to strong southwest wind today will transport this unconsolidated snow into fresh wind slabs in the alpine and treeline. In sheltered areas, this new snow will remain unconsolidated.
Below this new snow, consolidated snow from the previous weekend storm sits over a substantial crust that formed in early December. This crust is likely 20 cm thick (or more) and is present across aspects below 2400m. A thin layer of weak facets (sugary snow) can found above this crust.
The lower snowpack consists of a mix of various early season crusts and mainly moist snow. Snowpack depths range from 55-170 cm at treeline elevations and taper quickly below 1800 m.
Terrain and Travel
- Wind slabs are most reactive during their formation.
- Good day to make conservative terrain choices.
- Watch your sluff: it may run faster and further than you expect.
- Avoid convexities, steep unsupported terrain and rocky outcroppings.
Problems
Wind Slabs
This week, the region has seen 50cm of new snow that remains loose and unconsolidated in many areas. As the winds increase today and we receive another 10-20cm of new snow there will be a lot of snow available for transport creating fresh, reactive wind slabs in the alpine and treeline throughout the day.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 80-150 cm over a crust that formed in early December. This layer has not shown any recent avalanche activity, but has shown reactivity in recent snowpack tests. There is uncertainty around how this layer will react with increased load from continued snowfall and definitely warrants conservative terrain selection.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 18th, 2021 4:00PM
