Triggering large persistent slab avalanches is a serious concern this weekend. Conservative terrain choices are strongly recommended.
Multiple buried weak layers continue to produce large avalanches that propagate across terrain features. The layers are mostly composed of surface hoar and facet layers found between 60 and 150 cm deep. Most activity has occurred between 1800 and 2200 m.
A natural avalanche cycle occurred between December 26 and 28th that included large and very large (size 2 to 3) storm slab and persistent slab avalanches. While natural avalanche activity has slowed down, we continue to see notable human triggered avalanches.
There were multiple remotely triggered size 2 and 3 persistent slab avalanches in Bonnington and Kokanee areas on Thursday. These occurred on north and east facing slopes between the elevations of 1800 and 2200 m. Although just outside the boundary of this forecast, the photos in this MIN report illustrate the type of terrain where these avalanches are occurring. The failure layers were typically 60 to 80 cm deep and included both of the persistent weak layers discussed in the Snowpack Summary.
Looking ahead, triggering large persistent slab avalanches remains a serious possibility.
Around 30 to 40 cm of snow overlies a melt-freeze crust that extends up to 2000 m. Moist snow or a surface crust may be found below treeline.
Buried weak layers continue to show signs of instability. The two prominent layers of concern are a 60 to 80 cm deep layer of surface hoar and a crust on south aspects that was buried in mid-December and an 80 to 150 cm deep layer of surface hoar and facets that was buried in mid-November. Both of these layers have been most reactive between 1800 and 2200 m.
Saturday Night
Cloudy with trace precipitation, 10 to 20 km/h west wind, treeline temperature -7 °C.
Sunday
Mix of sun and cloud with no precipitation, 10 km/h northwest wind, treeline temperature -5 °C, freezing level 1000 m.
MondayMix of sun and cloud with no precipitation, 20 km/h south wind, treeline temperature -5 °C.
TuesdaySunny with no precipitation, 10 km/h southwest wind, treeline temperature -5 °C.
More details can be found in the Mountain Weather Forecast.
