Avalanche Forecast

Fair - Timing, track, or intensity of incoming weather is uncertain on Monday

High cloud moved across the region on Sunday afternoon that limited the extent of solar warming, but trapped warm air beneath the cloud layer that raised the alpine temperatures to near zero. The freezing level is expected to drop down to near valley bottom by Monday morning. A moist system is forecast to move north from south of the border on Monday morning. Some models show a narrow band of precipitation and warm air moving up into the Purcells. If this happens, the region may see 20-25 cm of snow at higher elevations, and rain below 1400 metres. Tuesday should continue to be unsettled as southwest winds increase during the day and the freezing level stays at about 1500 metres. Precipitation should start again on Wednesday morning and build to heavy by evening.

A natural cornice fall size 2.5 was reported from the high alpine on a NW aspect on Saturday. On Friday, a very large avalanche was triggered by a cornice in Gorman Lake (Dogtooth Range). It was wide, deep and covered sled tracks. Photos here: https://bit.ly/GMOYCv . There have been four other close calls in the Purcell Mountains this week, all involving very large slabs releasing either from a distance or with a light load. On Thursday, a snowmobiler remotely triggered a size 3.5 slab on an east aspect at 2400m at Oldman Creek, east of Quartz Creek (video here https://bit.ly/GLHIbg). It failed 1-2 m deep, was 200-300 m wide and ran full path, taking out mature timber. A second slope also failed, either remotely or sympathetically.

Warm alpine temperatures combined with strong solar radiation on Sunday caused moist snow up to about 2400 metres. The major concerns are the mid-February persistent weak layer, buried 1-2 m deep, and facets at the base of the snowpack. The February layer demands respect right now. It is very touchy and can be triggered remotely or by a light load on a variety of aspects, creating frighteningly large avalanches.