Avalanche Forecast

Fair - Intensity of incoming weather is uncertain on Friday

Thursday: A ridge of high pressure will bring dry and bright conditions with generally light northwesterly winds and freezing levels rising to around 2000m. Friday: A Pacific frontal system will bring around 5-10 mm precipitation, which may fall as a mix of snow and rain. Freezing levels will be up to 2000m. Winds will be strong southwesterly. Saturday: Another frontal system moves through late in the day, bringing further light to moderate amounts of precipitation, cooler temperatures and strong winds.

On Wedesnday, winds blowing from the northwest overloaded slopes facing south and east. There were reports of natural avalanches up to size 2.5, explosive-triggered avalanches up to size 3 and one skier-triggered avalanche, which was a size 2. This continues the trend from a very active natural avalanche cycle that reached it's height on Monday and is ongoing. I've left the previous avalanche narrative in from Monday/Tuesday, since the snowpack is healing only slowly and this information is still pertinent. From Monday/Tuesday, Size 3 avalanches were common, with some size 4. 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: http://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!: http://www.youtube.com/watch?v=UmSJkS3SSbA&feature=youtu.be

On Monday, approximately 30 cm of storm snow fell across the region 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.