Avalanche Forecast

Moderate - Forecast snowfall amounts are uncertain on Friday

THURSDAY NIGHT: Flurries start overnight with 5 cm accumulations by the morning, moderate west wind, alpine temperatures drop to -5 C.FRIDAY: Short period of intense snowfall with accumulations of 20-30 cm, strong southwest wind, alpine high temperatures around -2 C.SATURDAY: Cloudy with sunny breaks and isolated flurries with 2-5 cm new snow, light southwest wind, alpine high temperatures around -4 C.SUNDAY: Sunny with cloudy periods, light southeast wind, alpine high temperatures around -2 C.

On Monday, search and rescue responded to an avalanche in the Mount Seymour backcountry, which resulted in a fatality (see here for incident report). The avalanche occurred on a steep feature at treeline elevation. Avalanche professionals involved in the rescue indicated wide propagation consistent with a persistent slab problem. The crown depth was variable - 40 to 100 cm, indicating there was also wind loading in that area.Another persistent slab avalanche was reported on Wednesday (see MIN report here), and occurred naturally on a south-facing feature at treeline elevation.Last Friday and over the weekend, there was evidence of a widespread avalanche cycle up to size 2.5. These avalanches showed impressive propagation, with some being triggered remotely (from a distance) and some occasions stepping down to a 50 cm deep crust layer.

On Friday, 20-30 cm of new snow will form reactive storm slabs above new sun crusts and weak faceted snow. 40-80 cm of recent storm snow lies above a crust. The snow has bonded poorly to this crust and natural and human-triggered avalanche have been noted on this interface. These videos clearly demonstrate how easy it is to trigger this weak layer (here and here). The reactivity of this layer appears to be worse in the south of the region (i.e. the North Shore Mountains) since this part of the region has seen more snow and it has consolidated into more of a slab. Unusually for this region, we expect this layer to remain reactive for some time into the future. The lower snowpack is settled and strong.