Regions
South Coast Inland.
Sunday offers one last day of cool temperatures before warming arrives Sunday night. Pay attention to how the snow feels underneath you, as the storm snow settles into a more cohesive slab it will likely become more sensitive to human triggering.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
After a succession of snowstorms over southern BC, the weather over the lower mainland will settle into a dry period as 2017 comes to an end and 2018 begins. All indications point to the dry spell lasting until at least mid-week.SUNDAY: A few clouds, freezing level at valley bottom with an Above Freezing Layer (AFL) forming between 1800 m and 2500 m in the late afternoon. Moderate northwest wind, no snow expected.MONDAY: Scattered cloud, freezing level at valley bottom, Above Freezing Layer (AFL) between 1700 m and 2500 m, moderate west/southwest wind, no snow expected.TUESDAY: Clear skies at dawn, cloud cover increasing to overcast by the afternoon, freezing level at valley bottom, Above Freezing Layer (AFL) between 1500 m and 3000 m, light variable wind, no snow expected.
Avalanche Summary
No new avalanche activity was reported from Friday. A natural avalanche cycle likely occurred Friday night during the storm and may have continued into early Saturday morning. On Thursday a natural avalanche cycle was reported on steep unsupported features which produced storm slabs up to size 1.5 with crowns 10 to 15 cm in depth. A skier triggered size 1.5 avalanche on an unsupported feature at treeline was also reported.
Snowpack Summary
Friday night's storm produced about 30 cm in the north of the region and almost 40 cm in the south. That brings the total from the two successive storms to approximately 50 to 80 cm. The bulk of the wind during the storms was out of the southwest, south and southeast but there were periods of northeast and easterly winds too. All of this new snow rests on a variety of old surfaces including crust on solar aspects, old wind slabs, facets and isolated surface hoar below treeline. Wind slabs are common in wind exposed terrain, but it's thought the snow is largely unconsolidated in protected areas. As temperatures begin to warm the storm snow will likely settle into a more cohesive slab. A widespread melt-freeze crust buried mid-December exits throughout the region. This crust is down around 30 to 60 cm in the Duffey. Around the Coquihalla it's about 100 cm below the surface. This layer has not produced much in the way of avalanche activity, but it could come to life as the overlying slab gains cohesion.Beneath the mid-December crust, the lower snowpack is generally strong and well settled.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.