Regions
Kootenay Boundary.
There seems to be a high uncertainty with precipitation amounts for the region with an approaching Pineapple Express. However what is more certain is the region will be affected by strong winds and relatively high freezing levels.
Confidence
Poor - Timing, track, or intensity of incoming weather is uncertain on Friday
Weather Forecast
Friday: Thursday night into Friday a warm front associated with a Pineapple Express weather system will affect portions of the region. Unseasonably warm temperatures, strong westerly winds are forecast. Depending on the how the system tracks across the province, heavy precipitation is possible in the portions of the region. Freezing level 1700m.Saturday: Light precipitation, winds light southwest and freezing level of 2200m.Sunday: Light to moderate precipitation, light west winds, and freezing level of 1600m.
Avalanche Summary
Recent reports indicate ski cuts, skier remote and natural loose and slab avalanches to size 1.5 isolated to the storm snow. In the Kootenay Pass area, widespread whumpfing and cracking has been reported by folks traveling in the back country. It won't take much snow and wind to to overload the Buried February 12 surface hoar layer and make it likely for skier triggering.
Snowpack Summary
In much of the region, up to 80 cm recent snow overlies weak interfaces buried in mid-February (mainly surface hoar/ sun crust layers). The storm slab above these interfaces has the potential for wide propagations and surprisingly large avalanches, especially where winds have shifted the snow into slabs in the lee of terrain breaks. A thin freezing rain/rime crust formed last Friday, which is now buried by about 20-40cm snow. In the Rossland Range, surface hoar which was buried mid-week is 20-35 cm down and exhibits easy, sudden results in snowpack tests. As more snow builds over this layer, it could become touchy.Older snowpack weaknesses buried in the upper snowpack (Feb 4th and Jan 23 surface hoar/facet/sun crust layers) are still being tracked by professionals. There is some potential for triggering one of these deeper layers with a large trigger like an avalanche in motion, or from a thin-spot trigger point. The lower snowpack is generally well settled.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.