Avalanche Forecast
Issued: Dec 29th, 2023 4:00PM
The alpine rating is Persistent Slabs and Wind Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSeveral weak layers exist in the snowpack and human-triggered avalanches remain possible. Watch for signs of instability such as whumpfing.
Summary
Confidence
High
Avalanche Summary
On Thursday a large (size 2.5) naturally triggered wind slab avalanche was reported near Ashman. On Tuesday, a small (size 1) rider-triggered wind slab avalanche was reported in northeast-facing, treeline terrain by Hudson Bay Mountain. Whumpfing has been experienced by backcountry users in the Babines, Grizzly Plateau, and Hudson Bay Mountain recently. The whumpfing has been occurring mainly due to the surface hoar layers described in the snowpack summary.
Snowpack Summary
Recent incremental snowfall has been blown around forming wind slabs on mostly northwest through east-facing slopes at ridgetops. Southerly faces in the alpine are scoured down to the ground or an early-season crust. In most areas, two or more preserved surface hoar layers can be found buried between 35 cm and 80 cm deep. They appear to be most prominent at treeline and below but have been observed in some alpine locations as well.Snowpack depths at treeline are variable across the region with generally deeper amounts (~150cm) in the western part and shallower (~80cm) in the eastern part.The snow surface is likely moist or crusty up to treeline, and below 1100 m there is very little snow.
Weather Summary
Friday Night
Cloudy with 2 cm of snow expected, southeasterly winds 10-20 km/h, freezing level up to 1100m, and treeline temperatures falling to -4 °C.
Saturday
Cloudy with 2-5 cm of new snow, southerly winds 20-30 km/h, freezing level of 1400m and treeline temperatures rising to 1 °C.
Sunday
Mostly cloudy with no precipitation, westerly winds 10-25 km/h, high of -4 at treeline.
Monday
Mostly cloudy with a trace of new snow, variable winds 5-10 km/h, freezing level varies between 800m - 400m, and a high of -3 at treeline.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
Problems
Persistent Slabs
Several buried surface hoar layers exist in the snowpack and can be found 35 to 80 cm below the snow surface. This is only a problem above 1200m.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
15-20 cm of recent incremental snowfall has been blown around building slabs in open areas and on the lee slopes of ridgelines.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 30th, 2023 4:00PM