Avalanche Canada ldreier, Avalanche Canada

Kootenay Boundary Avalanche Forecast

Jan 12th, 2020 4:00PM

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

Snowfall is forecast to end by Monday morning. Moderate to strong west wind will form fresh slabs in lee terrain features throughout the day. If the wind affects below treeline elevations consider the avalanche danger Considerable at all elevation bands.

Summary

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

SUNDAY NIGHT: Cloudy with snowfall, accumulation 10 to 15 cm, light westerly wind, alpine temperature -12 C, freezing level dropping to valley bottom. 

MONDAY: Mix of cloud and sun with isolated flurries, moderate to strong west wind, alpine temperature -20 C, freezing level below valley bottom.

TUESDAY: Mostly cloudy with isolated flurries, moderate westerly wind, alpine temperature -18 C, freezing level below valley bottom.

WEDNESDAY: Mostly sunny, moderate westerly wind, alpine temperature -20 C, freezing level below valley bottom.

Avalanche Summary

On Sunday, a remote skier triggered size 2 avalanche on a deeper weak layer was reported (see MIN report).

On Saturday, numerous large (size 2) storm slab avalanches were triggered by explosives. Several small (size 1) and large (size 2) storm slab avalanches were triggered by skiers. A few small (size 1) natural storm slab avalanches were reported. 

On Friday, several skier triggered slab avalanches were reported up to size 2. Some of these avalanches were triggered remotely. Several small (up to size 1.5) natural avalanches were observed.

On Thursday, no new avalanches were reported, but one small (size 1) explosive triggered avalanche.

Snowpack Summary

The storm of the last days brought more than 40 cm of snow which partly fell with moderate to strong southwest wind. The formed slabs are sensitive to human triggers, particularly in exposed lee terrain features. More recent snow might hide slabs and make it trickier to navigate around them.

Deeper in the snowpack, a few layers of weak and feathery surface hoar may still be found around 70 to 130 cm deep. It is unclear whether they are still problematic and if so, how long they will be so for. The base of snowpack is also weak in parts of the region, where it consists of sugary faceted snow around a melt-freeze crust. Until these weak layers can be ruled out, best to travel conservatively.

Terrain and Travel

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Watch your sluff: it may run faster and further than you expect.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely-Very Likely

Expected Size

1 - 2

Around 10 to 15 cm of new snow are expected by Monday morning adding to more than 40 cm of low density snow of the last days. The wind shifted directions in the last days and new slabs will be formed with moderate to strong west wind on Monday and be particularly sensitive in lee terrain features in the alpine and around treeline. 

In areas with no wind affect the new snow is unconsolidated and fluffy. Be careful with sluffing in steep terrain, especially above cliffs and terrain traps.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3.5

Several persistent weak layers are buried in the snowpack. It might still be possible for humans to trigger them, or for storm or wind slab avalanches to step down to them and form very large avalanches.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 13th, 2020 5:00PM