Forecast snow and wind overnight on Sunday are expected to form fresh storm slabs reactive to human triggers, especially in wind-affected terrain.
Choose conservative terrain and watch for clues of instability.
Increasing snowfall amounts and winds will create touchy storm slabs at all aspects at treeline and above. Human triggers are likely on unsupported, convex rolls, especially on lee features. Be aware that slab avalanches could step down to deeper layers and produce larger-than-expected avalanches.
A crust with weak, faceted snow above and below exists near the base of the snowpack. Human-triggering this layer is unlikely, but large loads such as cornice fall or a smaller avalanche stepping down to this layer are possible. Avoid thin, rocky, wind-affected areas where triggering this layer is most likely. This layer is likely to be a concern for an extended period in this region. Read the new forecaster blog to learn more about this year's different snowpack.
Several small (size 1) human-triggered storm slabs were reported in the Brandywine and Whistler area on Saturday. These were intentionally triggered by skiers and failed within the recent storm snow on north-westerly slopes. Explosive controls also triggered slabs avalanches up to size 2 on immediate lee features around Whistler. The likelihood of avalanches will increase with the arrival of the forecast weather.
Up to 25 cm of new snow has fallen into the region since Friday. Ongoing southerly and previous northerly winds have affected the storm snow in any open terrain and near ridgelines. On sheltered slopes, up to 50 cm of powder storm snow can be found. Snow is heavy and moist at lower elevations.
In sheltered terrain at treeline, a weak layer of surface hoar may still be buried under the storm snow down 30 to 50 cm. A thick crust formed in late December is down 40 to 70 cm. Professionals are concerned that avalanches may run down to this crust. At lower elevations, this crust is up to 15 cm thick. In the alpine, it is thin and breakable.
Near the base of the snowpack, a weak facet/crust layer from mid-November can be found and remains a concern. In general, the snowpack is weak, faceted, and shallow.
A series of frontal bands will generate periods of moderate snowfalls Sunday night and Monday night. Overcast skies and dry conditions are expected Tuesday and Wednesday.
Sunday night
Snow 10-15 cm expected, moderate southerly winds gusting 45 km/h, freezing levels around 1000 m; low of -3C at treeline.
Monday
Cloudy with flurries up to 5 cm, moderate southerly winds gusting 45 km/h, freezing levels around 1200 m, high of -1C at treeline. Additional 15-20 cm overnight.
Tuesday
Cloudy; lingering flurries up to 5 cm, moderate southeasterly winds easing to light, freezing levels around 1500 m, high of +0C at treeline.
Wednesday
Cloudy, lingering flurries up to 5 cm, moderate southerly winds gusting 45 km/h, freezing levels around 1200 m, high of -2C at treeline. Additional 15-20 cm overnight.
More details can be found in the Mountain Weather Forecast.
