Forecast strong - extreme winds on Wednesday are driving the alpine danger to HIGH. It is a good time to stick to simple terrain.
Summary
Confidence
Moderate - Wind speed and direction is uncertain on Wednesday
Weather Forecast
A surface ridge sets up on Wednesday over the Interior keeping things mostly cloudy and dry. Ridgetop winds will blow strong and steady through Wednesday then start to back off Thursday night through the weekend. Wednesday: Mostly cloudy with alpine temperatures -8 and southwest winds 20-65 km/h.Thursday: Cloudy with snow amounts 5-10 cm. Alpine temperatures -8 and ridgetop winds 25 gusting to 70 km/hr.Friday: Isolated flurries with alpine temperatures -11 and ridgetop winds light from the southeast.
Avalanche Summary
On Monday numerous natural slab avalanches were reported up to size 2.5 on a variety of aspects and elevations. I would expect to see natural activity continue through Wednesday with forecast strong - extreme winds loading leeward slopes. Skier triggered avalanches are likely.
Snowpack Summary
Up to 60 cm of recent storm snow sits on a plethora of old snow surfaces including stiff wind affected snow, faceted (sugary) crystals and surface hoar crystals that formed in locations sheltered from the wind. The new snow will likely have a poor bond to these surfaces. Deeper in the snowpack exist two layers that may become reactive under the new load from the recent storm snow. The first being a spotty surface hoar layer that sits 40-100 cm down and the mid-November crust buried 100-200 cm deep. Snowpack tests on the crust have shown variable results from sudden to no result. Tracking and monitoring these potentially weak layers is important as they adjust to the new load of snow above.
swerner,
Avalanche Canada
