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Avalanche Forecast

Archived

Nov 28th, 2018–Nov 29th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Kootenay Boundary.

There is much uncertainty regarding the surface hoar just under the recent storm snow, we suspect it's primed for human triggering, but we have very few observations. Take a conservative approach, investigate and please post observations to the MIN.

Confidence

Low - Due to the number of field observations

Weather Forecast

The storm has passed, and we are now slowly transitioning towards a period of pronounced high pressure. The forecast period is marked by cooler temps, very little precipitation and the potential for clearing skies by the weekend.WEDNESDAY NIGHT: Freezing level holding around 1000 m, light variable wind, trace of precipitation possible. THURSDAY: Overcast, freezing level around 1400 m, light west/southwest wind, 1 to 5 cm of snow possible.FRIDAY: Broken cloud cover, freezing level around 1000 m, light west/southwest wind, trace of precipitation possible.SATURDAY: Scattered cloud cover, freezing level around 700 m, light northeast wind, no significant precipitation expected.

Avalanche Summary

A MIN report from Saturday describes a snowboarder triggering and getting caught in a smaller (size 1) storm slab that appeared to have been formed by cross-loading winds in the Ymir bowl area. See the full report on the MIN here.On Saturday November 24th in the Meadow Creek area of the neighboring South Columbias, a group of snowmobilers triggered a large deep persistent slab that released to ground and resulted in multiple involvements. Although still an isolated event, travelers should be aware of roughly similar snowpack characteristics in the Kootenay Boundary region and maintain cautious travel practices - especially in complex terrain at higher elevations. See the full report on the MIN here.Please submit any observations you have to the Mountain Information Network here.

Snowpack Summary

The storm that arrived Sunday night delivered 20 to 40 cm of snow to the region bringing alpine snow depths to between 70 and 90 cm. About 50 cm below the surface, just under the new snow, lies a persistent weak layer that was buried on November 21st. This weak layer consists of surface hoar (feathery crystals) in most places, but may present as a sun crust on steep south facing slopes. This surface hoar is thought to be widespread at treeline and below, but it may be found in sheltered alpine areas. A recent MIN report suggests that this layer was producing obvious signs of weakness at Kootenay Pass on Tuesday.At the base of the snowpack is a thick melt-freeze crust that formed near the end of October. This crust has shown limited reactivity thus far, but observations are very limited.

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.