New snow and extreme alpine winds will quickly form new wind slabs on Sunday and drive up the avalanche danger. Travel in wind loaded terrain is not recommended.
Summary
Confidence
Low - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A series of storm systems are going to hit the coast over the next few days but only light snowfall amounts are expected to reach most parts of the interior region. Snowfall amounts are expected to vary substantially throughout the region with the wettest parts seeing 20-30cm by Sunday evening. Alpine winds are forecast to be strong to extreme from the west in the morning and southwest in the afternoon. Freezing levels are expected to reach around 500 m by Sunday afternoon. Snowfall is forecast to continue Sunday overnight and Monday with models showing the potential for another 20-30 cm by the end of Monday in the wettest parts of the region. Alpine winds should remain strong to extreme and freezing levels will remain around 500 m. A break in the storm is currently forecast for Monday night with another storm pulse arriving on Tuesday.
Avalanche Summary
No recent avalanches have been reported in this region. On Sunday, the new snow with strong to extreme winds will quickly form new wind slabs. In the deeper snowfall areas to the south, a more widespread storm slab problem has the potential to develop by the end of the day. The new snow sits over a weak interface which is expected to increase the reactivity of new slabs.
Snowpack Summary
The new storm snow sits over a highly variable interface resulting from over a week of clear skies, cold temperatures, and strong outflow winds. This mid-December interface consists of scoured surfaces and hard wind slabs in wind exposed terrain, widespread faceting of the upper snowpack, and surface hoar in sheltered areas. The new snow is expected to bond poorly to this interface.Snowpack observations have been very limited recently. An old social media post near Smithers suggests there is a layer of surface hoar in the upper snowpack. The snowpack is very shallow throughout the region and widespread faceting of the entire snowpack is expected in most areas. A thick rain crust that formed in early November is probably near the bottom of the snowpack and is expected to be developing facets. A report from the Ningunsaw Pass area suggests that depth hoar is developing in shallow snowpack areas.
rbuhler,
Avalanche Canada
