Avalanche Forecast

Moderate - Intensity of incoming weather systems is uncertain

Sunday: 10-15 cm snow. Moderate south-westerly winds. Alpine temperature near -6.Monday: 20-30 cm snow. Moderate to strong south-westerly winds. Alpine temperature warming to near -2. Freezing level 1700m.Tuesday: 10-15 cm snow. Moderate south-easterly winds. Alpine temperature near -10. More information can be found in the Mountain Weather Forecast.

On Saturday we received preliminary reports of a human-triggered Size 2.5 avalanche in Glacier National park, on a south east aspect near 2400m. Also on Saturday we received reports of heavy snowfall in the Monashees with 30 cm accumulating in 5 hours! A widespread natural avalanche cycle occurred in these areas Saturday afternoon. Although the spike of avalanche activity from Wednesday has decreased, on Friday we still received reports of storm slabs to Size 2.5 running on northerly aspects above 1900m. Several persistent slabs to Size 3 were also reported on Friday, running naturally and also directly triggered by explosives (and showing good propagation).With incremental loading on Sunday, human triggering will remain likely and avalanches could be surprisingly large due to the structure of the snowpack.

Some areas in the Monashees received significantly more snow (30cm +) than was forecast on Saturday, resulting in a widespread natural avalanche cycle in the afternoon. Elsewhere in the region, 70 to 100 cm of storm snow sits on a layer of crust and/or surface hoar from mid-January. The crust is widespread, with the possible exception of high elevation north aspects. The recent storm snow fell with strong south winds, producing wind slabs in lee features at treeline and alpine elevations and in open areas below treeline.Deeper in the snowpack, the early-January persistent weak layer is buried 70 to 110 cm deep. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential, as well as other signs of instability such as whumpfs, cracking and avalanches. Yet another persistent weak layer buried mid-December is 100 to 150 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.A rain crust buried in November is 150 to 200 cm deep. While generally considered dormant, occasional activity has shown that it may react where it is less deeply buried.