Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Cariboos.
A Special Avalanche Warning has been issued for this weekend. A persistent slab sitting on a touchy weak layer will continue to produce large avalanches for several days after the storm ends.
Confidence
Poor - Due to the number of field observations
Weather Forecast
The warm, moist storm system will continue to produce precipitation on Thursday night and early Friday morning. An Arctic high pressure system will move into the region sometime during the day on Friday. Temperatures are expected to drop substantially on Saturday and persist for a few days.Thurs. night/Fri. morning: Precipitation 10-20mm, freezing level around around valley bottom, strong SW alpine wind. Friday afternoon: Precipitation tapering off, freezing level falling to valley bottom, alpine winds easing. Saturday/Sunday: Mostly sunny, treeline temperature around -20C, light N alpine wind.
Avalanche Summary
We haven't had any new reports since the weekend. If you have any observations, please send them to [email protected]. Recent observations from the Rogers Pass area where the conditions are expected to be similar include widespread natural activity up to size 3.5.
Snowpack Summary
The storm produced a slab up to 1 m thick which sits on the mid-November weak layer (facets, surface hoar, and/or a sun crust on steep southerly slopes). 20-30cm below this layer is a thick rain crust with weak facets on top. Snowpack data from the Cariboo region is very limited at the moment but I expect these layers are reacting similarly to the North Selkirk/Monashees as the formation conditions were generally the same. In the Rogers Pass area, the storm slab is poorly bonded to the mid-November layer and snowpack tests suggest it can be triggered easily with wide propagations possible. In some snowpack tests, the deeper crust/facet layer was also failing and it is possible that avalanches may step down to this layer.Recent strong and variable winds have probably created dense wind slabs in exposed terrain and resulted in variable snow distribution in the alpine. At lower elevations, expect travel to be difficult and potentially hazardous as many early season hazards are exposed or lightly buried (stumps, logs, rocks, open creeks, etc).
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.