Purcells

The next major storm is expected to start Wednesday night. If you're sick of seeing red, read the forecaster blog.

On Wednesday, a few natural avalanches size 2.5 were reported mainly on a NE aspect in alpine terrain. A size 2 avalanche was triggered remotely by a skier on a north aspect at 2000 m. On Tuesday, a size 3 avalanche occurred near Golden on an east aspect at 2300 m in response to intense wind loading. On Monday, several size 2-2.5 slabs released naturally (likely from wind-loading), which are suspected to have failed on the mid-February persistent weakness. A helicopter remotely triggered a size 1.5 slab, part of which stepped down to basal facets. A skier was also swept over a cliff in a size 1 slab which failed on the mid-Feb layer. On Sunday, a group of skiers triggered a size 3.5 slab 900m wide and 80-140cm deep on a north aspect in the southern Purcells. Late last week, large (size 2.5-3.5) human and explosive-triggered slabs were reported on all aspects, with crowns 40-120cm deep.

Good

A significant storm is expected to bring around 5cm new snow tonight and around 25-30cm on Thursday. Freezing levels are expected to peak at around 1700m on Thursday afternoon, meaning that some rain or sleet may fall at lower elevations during the storm. Ridgetop winds are expected to blow up to 90 km/h from the SW. On Friday, unsettled air that moves in behind the frontal system will continue to bring flurries or light snow, with around 5cm expected or maybe 10 cm to the south of the region. Winds should ease to moderate southwesterly. Freezing level will lower to around 1000m. On Saturday another storm could affect the region (models are disagreeing), bringing further snow and strong winds.

80 to 160 cm storm snow now overlies the prominent surface hoar layer of mid-February. The storm snow is reacting readily to both natural and human triggers. The mid-February surface hoar layer is more stubborn and not reacting everywhere, but has regularly been producing large avalanches up to size 3.5, which indicates it is very much still alive and needs to be treated with the utmost respect. This layer is widespread, so defining safe zones based on elevation or aspect may not be the best idea right now. Of course, shallower snowpack areas are those where you are more likely to trigger it, as well as convex rolls, and rocky or uneven terrain features. If you know that a slope has already avalanched on that layer, it may be a better bet, although you still need to factor in the effect of recent storm snow amounts and whether reloading is an issue. Operators continue to monitor basal facets, especially in shallow, rocky areas, but with all the recent storm snow, the basal weakness has not been of undue concern recently.