Purcells

The chance of triggering a persistent slab has dropped, but the consequences would be high.

Fair - Intensity of incoming weather systems is uncertain

Light snow is expected for each of the next three days (around 5 cm a day). Freezing level is at valley floor. Winds are generally light for the next three days, rising to moderate westerly on Monday.

A series of alarming large remotely-triggered avalanches was reported this week. On Wednesday, a size 3 slab was observed on an east aspect at 2200 m. This may have been remotely triggered by a skier. It started in the upper (January) persistent weak layer and stepped down to the deeper (December) weakness. On Tuesday, two persistent slabs up to size 2.5 were triggered remotely in the alpine. There was also a natural size 3.5 avalanche on an east aspect that was estimated to be about 200 cm deep and may also have been the mid-December layer. Explosives also triggered a size 2.5 slab on Thursday which failed on surface hoar over a metre deep.

A melt-freeze crust exists up to around 2200 m, overlying moist snow. At higher elevations, the surface is heavily wind affected. The depth of the mid-January surface hoar is highly variable across the region and it may have been destroyed by warmth at low elevations. Where it does exist, it can be found between 20 and 70 cm below the surface. The mid-December surface hoar layer lies below a strong mid-pack down about 60 to 120cm. Both of these persistent layers have been reactive recently. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It has been unreactive lately, but should be on your radar in shallow snowpack areas where there is more chance of triggering it.