Avalanche Canada ldreier, Avalanche Canada

Kootenay Boundary Avalanche Forecast

Jan 10th, 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.

The recent storm snow is gaining strength. However, it might still be possible to trigger deeper weak layers in the snowpack. If triggered wind or storm slab avalanches in-motion may step down to deeper weak layers and result in very large avalanches.

Summary

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Forecast snowfall amounts are uncertain.

Weather Forecast

FRIDAY NIGHT: Cloudy with snowfall, accumulation 5 to 10 cm, light southwest wind, alpine temperature -8 C, freezing level at 500 m.

SATURDAY: Cloudy with snowfall, accumulation 5 to 10 cm, light southwest wind, alpine temperature -6 C, freezing level rising to 800 m.

SUNDAY: Cloudy with snowfall, accumulation 5 to 10 cm, light to moderate westerly wind, alpine temperature -11 C, freezing level below valley bottom.

MONDAY: Mostly cloudy with snowfall, accumulation 5 to 10 cm, light to moderate westerly wind, alpine temperature -18 C, freezing level below valley bottom.

Avalanche Summary

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

On Wednesday, several natural and one skier triggered slab avalanche of size 3 were reported. Most of these avalanches released on a weak layer consisting of feathery surface hoar which was buried at the end of December and is now between 50 and 120 cm deep. One avalanche released in the storm snow and stepped down to the ground. Numerous explosive triggered storm slab avalanches of up to size 3 were reported.

On Tuesday, a widespread natural avalanche cycle occurred in the region with large storm slab avalanches to size 3.5. Numerous explosive and skier triggered storm slab avalanches up to size 2.5 were reported.

Snowpack Summary

Up to 15 cm of new snow is expected during the day adding to the new snow received on Friday. The last storm delivered around 40 to 70 cm of snow which fell with strong 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 50 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

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • Don't let the desire for deep powder pull you into high consequence terrain.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Possible

Expected Size

1 - 2.5

Up to 15 cm of snow are forecast during the day on Saturday adding to the new snow from Friday. The new snow might have formed wind slabs in lee terrain features in the alpine and around treeline where it was redistributed by moderate westerly wind. 

The previous storm delivered around 40 to 70 cm of snow in the region, forming a widespread natural avalanche cycle on Tuesday. Storm slabs may remain sensitive to human traffic.

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 11th, 2020 5:00PM