Dangerous avalanche conditions will develop as new snow accumulates on Monday.
A recent MIN report of an avalanche failing on surface hoar suggests reactive persistent slabs could be developing. Persistent slabs will become more reactive with the additional load of new snow. While there is uncertainty about the distribution of this problem, sheltered slopes around treeline elevations are most the suspect.
15-30 cm of new snow will form reactive slabs at higher elevations and in wind loaded terrain.
SUNDAY NIGHT: Cloudy with flurries starting early in the early hours of Monday morning, moderate wind from the southwest, alpine temperatures around -5 C.
MONDAY: Frontal system intensifies throughout the day with 15-30 cm of snow by the afternoon as snow level rises from valley bottom to 800 m in the evening, strong wind form the southwest, alpine high temperatures around -2 C.
TUESDAY: Storm continues Monday night with another 10-20 cm of snow above 1000 m (rain below) then clearing by Tuesday afternoon, strong wind from the west, alpine high temperatures around -2 C.
WEDNESDAY: Cloudy with scattered flurries and up to 5 cm of snow, light wind, alpine high temperatures around -5 C.
The incoming storm will create unstable storm slabs and add stress to buried weak layers on Monday and Tuesday. A size 1.5 skier-triggered avalanche was reported on the MIN on Friday (see full report and photos here). The avalanche occurred on a convex north-facing slope at treeline and failed on a surface hoar layer 50 cm below the surface. This is the first avalanche reported in the region the past few days, but highlights a potential persistent slab problem that could produce larger avalanches on bigger terrain features.
20-40 cm of new snow is expected between Monday morning into Monday night. Mild temperatures and strong wind will make this new snow form reactive slabs. Reports suggest there are two layers of surface hoar buried 25-50 cm below the surface. A skier triggered avalanche at Ashman and snowpack test results near Smithers suggest these layers have now become reactive (see these recent MIN reports). There is uncertainty about the distribution of this layer, but the sheltered slopes around treeline elevations are the most suspect for having preserved surface hoar.
