Heavy rain followed by rapid cooling has helped stabilize the snowpack and lower avalanche danger. Unfortunately it's probably damaged the snow quality too!
Confidence
Fair - Due to the number of field observations
Weather Forecast
We’ve seen a big change in the weather pattern from earlier in the week. A push of cold Arctic air from the north is invading the Province all the way down to the South Coast. As the Arctic front passes on Friday afternoon (with an associated trough and moisture) we could see snow flurries all the way to valley bottom. By Saturday morning we could see up to 5-10 cm in the mountains. The Arctic air pushes further south on Saturday leaving us in cold and dry air for the next few days. Treeline temperatures should hover between -8 and -12.
Avalanche Summary
Numerous loose wet and wet slab avalanches up to size 2 were reported near Whistler on Wednesday and Thursday as temperatures spiked and rain fell to 2000 m. Rapid cooling on Friday morning has helped stabilize the snowpack but it may be possible to trigger dense storm slabs higher in the alpine (above 2000 m).
Snowpack Summary
Heavy precipitation gave way to clearing skies and rapidly cooling temperatures early on Friday morning. Most areas saw heavy rain up to at least 2000 m this week. Above this it's possible that dense storm slabs and fresh cornices formed. Where it did rain, the snowpack is probably frozen solid with a dusting of fresh snow on top. The lower elevation snowpack has also thinned significantly. A weak layer of facetted snow on a crust was buried around 50-60 cm deep before the rain. This weakness may have been flushed out or may now be bridged by a solid ice crust; however, there is no new info on this interface so it would be wise to investigate its existence and strength before venturing into bigger terrain.
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.