Kootenay Boundary Avalanche Forecast

Issued: Jan 8th, 2022 4:00PM

Sun Jan 9th Current Conditions
Alpine Considerable Treeline Moderate Below Treeline Moderate
Mon Jan 10th 2 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate
Tue Jan 11th 3 Day Outlook
Alpine Considerable Treeline Moderate Below Treeline Moderate

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Persistent Slabs.

Wind has produced deeper and more reactive deposits in lee features. Be especially mindful around steep and convex openings in the trees and ridge features in the alpine.

Summary

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Saturday night: Mostly cloudy with isolated flurries. Moderate SW wind. Treeline low around -12 °C. 

Sunday: Mix of sun and cloud. Moderate SW wind. Treeline high around -3 °C. 

Monday: Sunny. Light and increasing S wind. Treeline high around -2 °C. 

Tuesday: Incoming flurries, 5-10 cm. Moderate gusting to extreme SW wind. Treeline high around -3 °C. 

Avalanche Summary

A natural avalanche cycle to size 2 occurred overnight Thurs-Fri with accumulating snowfall and wind. On Friday morning, explosives easily triggered storm slabs to size 2.5.

On Wednesday, wind slabs were reactive to explosives up to size 2 in the west of the region. On Monday and Tuesday, storm slab avalanches were reactive naturally and to skier and explosive triggers, up to size 2.

There has been an alarming pattern of large, persistent slab avalanches being consistently reported over the past two weeks. Almost all of these avalanches ran on the early December weak layer. Deeply buried persistent problems like these don't go away overnight, and it remains a serious concern. Additional loading by the weight of new snow will further stress this weakness and may result in a resurgence of reactivity.

  • On Tuesday, explosive control work near Rossland produced a size 2.5 persistent slab avalanche on a layer of surface hoar from late December. 
  • On Monday in the neighboring South Columbia region, a natural size 2.5 persistent slab avalanche was reported on a NE aspect at 2200 m failing 80 cm deep on the early December layer.
  • A few notables from last week feature in our latest blog Photos of recent persistent slab avalanches in the southern interior. 

Snowpack Summary

15-30 cm of new snow accumulated by the end of Friday was accompanied by southwesterly wind and warming temperatures, resulting in a denser slab forming over lower density snow. An accumulated total of 60-80 cm of new and recent snow now sits over variable and potentially weak snow surfaces including widespread facets, wind affected snow, and/or surface hoar up to 5 mm in sheltered areas.

The early December crust/facet layer has been responsible for sporadic but very large persistent slab avalanches over the past two weeks. The crust is now buried 120-200 cm deep except in thin, wind affected areas near ridgetops where nearly all of the recent avalanches have been triggered. We have uncertainty around whether new snow loads will cause this layer to fail naturally in the short term, or to help it heal in the longer term.

Terrain and Travel

  • Give the new snow time to settle and stabilize before pushing into bigger terrain.
  • Caution around convexities or sharp changes in terrain.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely

Expected Size

1 - 2

Increasing winds will build fresh slabs. Be especially mindful around steep and convex openings in the trees and ridge features in the alpine.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Unlikely-Possible

Expected Size

2 - 3

A deeply buried weak layer has produced a number of large and surprising avalanches in the past week and a half. As new snow loads and smaller storm slab avalanches further stress this layer, we may continue to see avalanche activity on it. This problem is most likely to be triggered from thin or variable depth snowpack areas such as wind affected features, ridge crests, and near rocky outcroppings.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 9th, 2022 4:00PM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.