Purcells

Fair - Timing or intensity of solar radiation is uncertain

Until yesterday the weather story was all about snow with the last storm starting warm and finishing cold. Monday overnight a cold front came through. Looking forward the story for Wed & Thurs is sunshine - warm temperatures and SOLAR WARMING. Freezing overnight. Moderate NW winds. Friday becoming cloudy, maybe flurries ahead of the next forecast system.

Widespread natural avalanche cycle Monday with storm, wind, and warm temperatures; size 3 avalanches common, some size 4 likely. Timber fell. Observations limited by clouds, fog, and snow in the air so we won't know the full extent of the cycle until Tuesday's reports are tallied. One remotely triggered avalanche triggered from 300m away caught my eye - it speaks to the propagation potential of the surface hoar now deeply buried. If this layer is triggered the avalanche will be big; this layer can be triggered from below so be mindful of overhead hazard. This layer will not go away in the next few days. Also, a sledder triggered a size 3 avalanche in the Quartz Creek area and while the machine is reportedly totaled, the rider is okay.There are two great observations from professionals working in the region recently. The first one can be found on the MCR, it talks about the widespread & sensitive nature of the SH in the Northern Purcells. You can start here and work your way into the March observations: https://www.acmg.ca/mcr/archives.asp The other is in the form of a youtube video which also deals with the surface hoar, highlighting the potential for remote triggering and large propagations when this layer fails. Check out the shooting cracks in the video. Wild!: https://www.youtube.com/watch?v=UmSJkS3SSbA&feature=youtu.be

See avalanche observations below. 30 cm of storm snow fell across the region during daylight hours Monday accompanied by winds out of the W/NW & W/SW at speeds capable of wind slab formation. Another 15cm arrived overnight before the cold front arrived. A cohesive slab continues to settle over the mid-February surface hoar, which is now down 70 to 150 cm. Recent reports include whumpfing and cracking, and moderate but sudden compression test results. This persistent weakness is susceptible to remote triggering and has the ability to propagate in low angled terrain, and the overlying slab structure creates the potential for step-down avalanches. Basal facets have only been reactive on steep, shallow, and rocky slopes, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are the most suspect locations.