Triggering slab avalanches is possible on steep terrain features in the alpine and at treeline.
Recent snow has likely formed unstable slabs in steep terrain at higher elevations, especially around ridges and convex rolls.
A recent MIN report of an avalanche failing on surface hoar suggests reactive persistent slabs could be developing. Sheltered slopes around treeline elevations are most suspect, but there is uncertainty about the distribution of this problem. Gather information about this problem as you approach avalanche terrain.
SATURDAY NIGHT: Light flurries delivering a few cm of snow, 20-40 km/h wind from the southwest, alpine temperatures around -5 C.
SUNDAY: Mostly cloudy with isolated flurries and up to 5 cm of new snow, 20-30 km/h wind from the southwest, alpine high temperatures around -3 C.
MONDAY: Next frontal system arrives bringing 5-15 cm of snow by the afternoon, 40-60 km/h wind from the southwest, freezing level up to 1000 m with alpine high temperatures around -2 C.
TUESDAY: Stormy weather continues with another 5-15 cm of snow, 30-50 km/h wind from the southwest, alpine high temperatures around -2 C.
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.
Sheltered terrain has 10-30 cm of low density snow, while exposed terrain has been affected by recent wind from the southwest. Reports suggest there are two layers of surface hoar buried 25-50 cm below the surface. A skier triggered avalanche on one of these layers on Friday suggests the snow above this layer has likely developed into a reactive slab in certain parts of the region. 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.
