Touchy new wind slabs are expected on Thursday throughout the region.
There is uncertainty about the track and intensity of the storm, and areas around the Coquihalla may see more snowfall than the rest of the region. With more than around 25 cm new, treat the danger as HIGH.
New wind slab formation is expected at higher elevations on Thursday. If you are seeing more than around 25 cm of new snow, a more widespread storm slab problem should be expected.
Wet loose avalanches are possible on steep slopes at lower elevations where the storm produces mainly rainfall.
A storm system impacts to the coast Wednesday night and Thursday before a warm ridge of high pressure establishes on Friday.
Wednesday Night: Snowfall 5-10 cm, wind becoming strong SW, freezing levels 1200-1400 m.
Thursday: Snowfall 10-15 cm, strong SW wind, freezing levels reaching around 1500 m.
Friday: A mix of sun and cloud, light to moderate NW wind, freezing levels climbing to around 3000 m with an inversion.
Saturday: Mainly sunny, light NW wind, freezing levels around 3000 m with an inversion.
On Tuesday, a ski cut triggered a size 1 wind slab on a NE aspect at 1950 m in the north of the region failing down 30 cm on a crust. A size 1.5 wind slab was also remotely triggered from a ridge on a NW aspect at 1950 m.
The new snow continues to bury a widespread crust which extends into alpine elevations. There have also been reports of a layer of small surface hoar above this crust in the north of the region. Reactive wind slabs have been reported recently and new wind slabs will continue to develop during the storm on Thursday.
The early December crust/facet layer is now typically down 100-150 cm but may be as shallow as 60 cm and as deep as 200 cm with lots of variability through the region. The layer is most prominent between 1700 and 2100 m. The crust appears to be breaking down in the south of the region but remains a concern in the north. The layer has been dormant recently but is a concern for the period of major warming and sun forecast for the weekend. The most likely place to trigger it would be in thin, rocky snowpack areas where it is shallowest.
