Avalanche Forecast
Regions: Birkenhead, Duffey, South Chilcotin, South Coast Inland, Stein, Taseko.
If I had to pick one region in the southwest to trigger a destructive persistent slab, this would be it. The problems are in play, new snow and wind will add to their reactivity and consequence.
Confidence
High
Avalanche Summary
Wednesday's reports showed 15-20 cm of new snow becoming reactive with warming and yielding many skier-triggered avalanches to size 1 and naturals to size 2 in the MacGillivray Pass area. At least one size 2 ran on our early February facet/crust layer.
Reports from Thursday support these observations of instability with local operators noting widespread cracking of storm snow above the early February facets as well as small ski cuts stepping down to the crust below.
Snowpack Summary
Up to about 10 cm of new snow should fall in the region through Saturday. It will bury sun crust on solar aspects but mainly add to 15 - 20 cm already overlying previous surfaces that include crust on south aspects and lower elevations, faceted snow and/or small surface hoar in sheltered features, and previously wind-affected surfaces in the open.
Roughly 40 - 50 cm of snow now sits above a widespread crust from late January. Weak grains like facets or more isolated surface hoar may be found above this crust. Especially with the load above it increasing, this problematic layering remains a concern with ample recent avalanche activity and snowpack tests showing its potential.
Weather Summary
Friday night
Cloudy with flurries bringing less than 5 cm of new snow. 20 - 30 km/h southwest alpine wind. Freezing level falling to valley bottom.
Saturday
Cloudy with scattered flurries bringing less than 5 cm of new snow. 20 to 30 km/h southwest alpine wind. Treeline temperature -2 °C with freezing level to 1500 m.
Sunday
Cloudy with flurries bringing 5 - 15 cm of new snow, including overnight amounts. 40-50 km/h southwest alpine winds. Treeline temperature -3 °C with freezing level to 1500 m, falling sharply in late afternoon.
Monday
A mix of sun and cloud with isolated flurries. 10-15 km/h southwest alpine wind. Treeline temperature -5 °C with freezing level at valley bottom.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Wind slabs are most reactive during their formation.
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Persistent Slabs
Recent observations show the problematic early February layer of facets on crust becoming increasingly triggerable. Avalanches triggered on this layer will be destructive.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2.5
Wind Slabs
Light new snow and elevated southwest winds will add to recent slabs in the lee of ridges and exposed terrain features.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2