Northwest Coastal

Heavy snowfall, extreme winds, and a buried surface hoar layer are a recipe for very dangerous avalanche conditions.

Moderate - Due to the number of field observations

FRIDAY: 10-15 cm Thursday night and another 15-30 cm during day on Friday, 60-90 km/h winds from the southwest, freezing level up to 1000 m.SATURDAY: 10-15 cm overnight and 5-10 cm during the day, 30-60 km/h winds from the southwest, freezing levels dropping to 500 m.SUNDAY: cloudy with isolated flurries, light winds, cooling with treeline temperatures around -10.

On Wednesday, several size 1.5-2 storm slabs were triggered by explosives on steep north aspects between 1400-1500 m in the Stewart area. A natural size 1 avalanche was triggered by a rockfall in the area running on a 20-50 cm deep surface hoar layer. A MIN report from the Terrace area describes evidence of a natural avalanche cycle from the past few days with up to size 2.5 storm slabs in large alpine features. The incoming storm will build bigger storm slabs and has the potential to reawaken buried surface hoar layers.

Heavy snowfall and extreme southwesterly winds will form touchy storm slabs on Friday. Storm snow totals could reach 30-50 cm by Friday afternoon, with the potential for much more on lee features. The new snow will load a buried surface hoar layer reported 60-80 cm below the surface in many parts of the region. On Wednesday, a ski tourer reported numerous whumpfs caused by the surface hoar layer in the Terrace area. Also, snowpack tests indicated the layer can be triggered with moderate loads and has the potential to propagate over long distances. A thick rain crust exists 20-30 cm below the surface hoar layer, with isolated reports of weak facets forming above the crust. Treeline snow depths are around 120-140 cm in the Terrace and Stewart areas, but substantially less further north. Snow in these thinner areas, such as Ningunsaw, may be facetting and developing weak basal layers.