Avalanche Canada ghelgeson, Avalanche Canada

Kootenay Boundary Avalanche Forecast

Jan 13th, 2020 4:00PM

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

The snowpack needs time to adjust to all of the new snow & wind. Strong north wind may have formed fresh slabs in unusual locations at all elevations. We all need to scale the terrain choices back to simple well-supported features for the next few days.

Summary

Confidence

Low - Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

After a stormy period it looks like the intensity of the weather will back off for the next few days with quite cold temperatures, dribs and drabs of snow and a consistent wind out of the southwest.

MONDAY NIGHT: Freezing level at valley bottom, light to moderate southwest wind, no significant precipitation expected.

TUESDAY: Scattered cloud cover, freezing level at valley bottom, light to moderate southwest wind, trace of snow possible.

WEDNESDAY: Scattered cloud cover at dawn clearing through the day, freezing level at valley bottom, moderate to strong southwest wind, trace of snow possible.

THURSDAY: Broken cloud cover, freezing level at valley bottom, light to moderate southwest wind, 2 to 8 cm of snow possible.

Avalanche Summary

Both natural and explosive controlled avalanches up to size 2.5 were observed Monday on all aspects above 1800 m. Loose avalanches to size 1.5 were also widely reported.

On Sunday the bulk of the avalanche activity was limited to loose dry avalanches but a spooky avalanche was remote triggered by a group of skiers, more details and photos in this 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.

Snowpack Summary

The storm of the last days brought up to 60 cm of snow which fell with moderate to strong southwest wind before winds switched to the north/northeast Sunday night. The resulting wind fueled storm slabs likely remain 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 or not 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

  • Give the new snow several days to settle and stabilize before pushing into bigger terrain.
  • Avoid freshly wind loaded terrain features.
  • Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.
  • Avoid lingering or regrouping in runout zones.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely

Expected Size

1.5 - 2.5

20 to 40 cm of snow fell in the region Sunday into Monday which makes for 60 to 145 cm in the last week. The wind shifted direction Sunday night and new slabs have likely formed in unusual locations. These may be particularly sensitive in lee terrain features in the alpine and around treeline.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

2.5 - 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 14th, 2020 5:00PM