Purcells

Cool conditions are expected to improve stability this week but tricky conditions may persist on Wednesday, especially at higher elevations. Wind and persistent slabs may still be reactive to human-triggering and very large avalanches are possible.

Fair - Freezing levels are uncertain

A ridge of high pressure builds on Wednesday and should result in mainly dry conditions for the next few days. On Wednesday, a mix of sun and cloud is expected with moderate-strong alpine winds from the NW that should ease through the day. Isolated flurries are possible. Freezing levels are expected to fall below 1000m Tuesday overnight and then reach around 1500m on Wednesday afternoon. On Thursday and Friday, similar conditions are expected with mainly dry conditions, a mix of sun and cloud, and light alpine winds. Freezing levels are expected to reach 1600m on Thursday afternoon, 1800m on Friday afternoon, and below 1000m during each overnight period.

On Monday, a cornice triggered a size 2 storm slab was reported at 2600m on a NE aspect.  Loose wet sluffing was also reported from lower elevations. On Sunday, several natural avalanches up to size 2 were reported but no details were provided. These could be new storm slabs or could be failing on deeper layers resulting in persistent slab avalanches. A couple of small skier-triggered soft slabs were triggered on Saturday, most likely from wind loaded features. On Thursday and Friday, wind and warming were responsible for several natural slab avalanches up to size 3, mainly on east and north aspects above 2100 m. There was also a report of a close call, skier triggered size 2.5 slab avalanche in the Dogtooth range.  Natural avalanches are generally not expected on Wednesday if there is good overnight recovery but may still be possible in isolated areas. Human-triggered wind slabs and persistent slabs are still a concern, especially on steep, unsupported slopes in the alpine. Stability is generally expected to improve with the cooling trend but this may take a few days and touchy conditions may still exist on Wednesday.

20-30cm of heavy storm snow overlies a thick rain crust that formed last Friday when it rained into the alpine. A new surface crust is expected to be widespread on Wednesday after freezing levels drop Tuesday overnight. On Monday, moist snow was being reported to around 2500m so the crust will likely extend well into the alpine. In the high alpine, strong winds have redistributed the new snow and wind slabs can be expected in leeward terrain features. Several persistent weak layers exist in the upper 1m of the snowpack and remain a concern. In the north of the region, the mid-March crust/facet layer is down 40-60cm and remains a concern. Just below this layer is the mid-February crust/facet/surface hoar layer which may also still be reactive in isolated areas. These layers have the potential for wide propagations and large avalanches remain possible.