Overnight cooling will play a key role in how the snowpack recovers from recent warm temperatures and rain. Travel conservatively and avoid overhead hazards—if the sun comes out, solar slopes will be suspect.
A persistent weak layer is buried 90-130cm deep. This persistent weak layer is made up of surface hoar at treeline and below. On solar aspects in the alpine and treeline this PWL is a suncrust. Storm slabs could step down to these layers, magnifying the avalanche size.
Up to 60cm of snow, accompanied by strong winds and mild temperatures, created a reactive storm slab. Expect this storm slab to be failing naturally if the sun comes out (ie Frequent Flyer in the Connaught drainage). They will be sensitive to human triggering.
Artillery control in Rogers Pass from Jan 12 produced many avalanches from sz 2.5 to 3.5. Natural avalanches before control commenced were running to valley bottom in the Tupper/Macdonald corridor. Natural avalanche activity has decreased with the storm passage.
In the last wee, neighbouring ski operations reported storm slabs triggered both naturally and by humans up to sz 2.
In summary, the snowpack consists of a heavy, warm, and widespread storm slab sitting over a well-settled mid and lower snowpack. Above-freezing temperatures have reached into the alpine, and once temperatures drop, this will form a problematic breakable crust.
A January 1 persistent weak layer remains buried 90–130 cm deep. At treeline and below it is surface hoar in sheltered areas, while above treeline and into the alpine it is expressed as a crust on solar slopes.
The pattern changes as cold air moves in from the north.
Tonight: Mainly cloudy. Alp low -7°C. Winds SW 35km/h. Freezing level (FZL) 1800m
Thurs: Cloudy with sunny periods. Alp high -7°C. Winds NW 15km/h. FZL 1100m
Fri: Sunny with cloudy periods. Alp high -3°C. Winds NW 10km/h. FZL 1200m.
Sat: Sunny, Alp high 0°C. West winds 10km/h. FZL 1700m. Alpine temp inversion.
