The warm, wet, windy storm continues. Backcountry ski conditions are reported to be terrible and avalanche hazard remains elevated. Now is a good time for indoor activities or take your rain gear with you to your local ski hill.
Confidence
Fair - Timing of incoming weather systems is uncertain
Weather Forecast
The sub-tropical storm system continues to produce similar weather conditions on Thursday. Freezing levels will be around 2000m, alpine winds should remain strong, and we can expect another 5-15mm of precipitation. Things start to change on Friday morning as freezing levels should drop below 1500m and alpine winds ease during the day. Lingering precipitation is expected on Friday with amounts around 3-6mm. A ridge of high pressure is expected to begin to build on Saturday resulting in a mix of sun and cloud. Freezing levels are expected to be back down near valley bottom and winds should be calm or light.
Avalanche Summary
We haven't received any observations from the Cariboos since the storm started. The conditions are expected to be very similar in the North Columbia region where widespread natural avalanche activity up to size 2.5 was reported on Tuesday. See the North Columbia - Monashees and Selkirks bulletin for more details.
Snowpack Summary
Rain to high elevations is saturating the upper snowpack. A wet snow surface is expected up to 2000m elevation and moist snow to around 2400m. Strong winds are loading leeward features in the alpine. Below the new storm snow may be a layer of surface hoar which was buried on Dec 5. About 1 m down, a weak layer of surface hoar and/or facets can be found in some locations. A thick rain crust with facets from early November is buried around 1.2 m down. Snowpack tests on these deep weak layers are showing slowly improving results, but in some locations these layers are still reactive and have the potential to release large slab avalanches. We may see these deep weak layers become a problem again as the storm continues to add new load.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.