South Coast

A storm slab sitting on a touchy weak layer means conditions will remain tricky over the next few days. Continue to make conservative decisions and have a safe holiday.

Fair - Timing, track, or intensity of incoming weather system is uncertain

Conditions on Wednesday will be unsettled as the storm is replaced by a ridge of high pressure that will establish itself for Thursday and Friday. The freezing levels on early Wednesday are expected to drop before the precipitation ends so we may see some snow at lower elevations. By Wednesday afternoon the precipitation should have ended but scattered flurries are possible. Freezing levels should drop to around 800m and alpine winds should taper off to light from the NW. Thursday is expected to be mostly sunny with freezing levels around 600m and light alpine winds. Friday will be similar with a mix of sun and cloud, freezing levels around 600m, and light alpine winds.

On Monday we received a report of storm slabs up to size 2.5 being remote-triggering from flat areas up to 75m away in the Coquihalla area between 1600 and 1900m elevation. Slabs were 40-70cm thick and were releasing on the crust/surface hoar layer. On Sunday, natural storm slab activity up to size 2 were reported at treeline and in the alpine. Natural activity is expected again on Tuesday and Wednesday with additional storm loading.  Check out this observation from Sunday ( https://goo.gl/8G2Xeu ) which shows the relatively mellow terrain on which avalanches are occurring. 

The new snowfall is sitting on the storm snow from the weekend which is typically 30-60 cm deep and sits above the mid-December crust/facet/surface hoar layer. The slab tends to be thinner in the north of the region. The crust typically extends to around 2200m elevation and the surface hoar that sits above is typically 2-5mm where it exists. In some areas, the new snow may be well bonded to this layer but in other areas the layer remains highly reactive so some local investigating may be required. Strong forecast winds on Tuesday/Wednesday morning are likely forming touchy new wind slabs. The November crust is deeply buried near the ground and while triggering this layer is generally unlikely, the likelihood of triggering does increase during the storm with the additional weight of the new snow.