Avalanche Canada ldreier, Avalanche Canada

Kootenay Boundary Avalanche Forecast

Jan 11th, 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.

10 to 20 cm snow overnight and more during the day might form reactive slabs in lee terrain features where the snow is exposed to wind from the southwest. The avalanche danger will increase throughout the day with increasing snow amounts and wind.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

SATURDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm with highest amounts at Kootenay Pass, light westerly wind, alpine temperature -10 C, freezing level at 500 m.

SUNDAY: Cloudy with snowfall, accumulation 10 to 20 cm, light to moderate southwest wind, alpine temperature -10 C, freezing level at 500 m.

MONDAY: Mostly cloudy with snowfall, accumulation 5 to 15 cm, light westerly wind, alpine temperature -15 C, freezing level below valley bottom.

TUESDAY: Mostly cloudy with flurries, accumulation 5 to 10 cm, light to moderate westerly wind, alpine temperature -15 C, freezing level below valley bottom.

Avalanche Summary

On Saturday, a skier triggered storm slab avalanche of size 2 fully buried a person. The person was rescued by companions and sustained no injuries. A few small (size 1) natural and skier triggered storm slab avalanches were reported. Numerous large (size 2) storm slab avalanches were triggered by explosives.

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 20 to 40 cm of snow which fell with moderate southwest wind. The formed slabs may still be sensitive, particularly in exposed lee terrain features. 

Deeper in the snowpack, a few layers of weak and feathery surface hoar may still be found around 70 to 150 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

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely

Expected Size

1 - 2

Around 10 to 20 cm of snow are expected overnight and another 10 to 20 cm during the day. The new snow will form slabs in lee terrain features in the alpine and around treeline where it will be redistributed by moderate southwest wind. This storm will hide wind slabs which were formed on Friday by westerly wind. Expect sluffing to happen in areas where the storm snow is not affected by wind. 

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 12th, 2020 5:00PM