Purcells

Surface instabilities and cornice hazards should be firmly on your radar as you travel. Expect stability to deteriorate over the course of each day.This is our final regular forecast of the season and will expire on April 25.

Moderate -

Tuesday: Sunny. Light southwest winds, moderate to strong at ridgetop. Freezing level to 3100 metres with alpine high temperatures around +3. Weak overnight cooling.Wednesday: Sunny. Light northwest winds. Freezing level rising from 2500 to about 3500 metres by evening and staying steady overnight. Alpine high temperatures around +4.Thursday: Sunny. Light south winds. Freezing level to 3700 metres with alpine high temperatures around +8.

Decreasing traffic in the mountains have limited avalanche observations over the past few days, however numerous loose wet avalanches up to size 2.5 were observed in the northern part of the region on Sunday. These occurred on steeper east-facing slopes at 2600 metres and below.Another round of explosives control in the north of the region on Thursday yielded several cornice and loose dry releases, as well as one more concerning size 3 persistent slab release that featured an 80-200+ cm crown fracture. This occurred on a north aspect at 2450 m. Numerous natural loose wet releases (to size 2.5) and several other recent natural storm slabs (to size 3) were also noted.A natural size 3 slab release was observed on Wednesday and is believed to have released over a persistent weak layer from mid-March. One explosives-triggered size 3 deep persistent slab was also reported.Looking forward, a period of increasing warming, full sun, and warm overnight temperatures will be maintaining elevated chances of cornice and loose wet avalanche activity.

A surface crust is likely to exist on all but north aspects above 2200 metres and is expected to undergo melt-freeze cycles with daily warming and overnight cooling. Below the surface, a variable 30-70 cm of settled storm snow from the past couple of weeks covers another supportive crust which shares similar distribution to the upper crust. This layer as well as the deeper (down about 60-100 cm) mid-March crust are of limited concern concern after warm temperatures have promoted settlement and bonding in the upper snowpack. Any remaining uncertainty with regard to their strength is generally limited to high north aspects and the possibility for triggering with a heavy load, such as a cornice collapse.Deeper persistent weak layers from December and January are considered dormant at this time, but some of these deep layers are more prominent in shallow areas of the Purcells than in other parts of the interior. Periods of intense warming are the most likely times for any natural release to occur over a deep persistent layer as well as for cornice triggers to be more numerous.