Avalanche Canada ghelgeson, Avalanche Canada

Kootenay Boundary Avalanche Forecast

Jan 14th, 2020 3:00PM

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 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. Uncertainty is due to the extreme variability of wind effect on the snowpack.

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 consistent wind out of the southwest.

TUESDAY NIGHT: Freezing level at valley bottom, light to moderate southwest wind, 1 to 5 cm of snow possible.

WEDNESDAY: Overcast at dawn clearing through the day, freezing level at valley bottom, moderate to strong southwest wind, 1 to 5 cm of snow possible.

THURSDAY: Broken cloud cover, freezing level at valley bottom, light to moderate southwest wind, potentially stronger at ridge top, 5 to 10 cm of snow possible.

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

Avalanche Summary

This region has been a hot spot for recent avalanche activity. A number of large natural avalanches up to size 3 were reported on east, southeast and south facing slopes above 2000 m in the Rossland area Monday with crowns up to 100 cm in depth.

In the rest of the region both natural and explosive controlled avalanches up to size 2.5 were observed on all aspects above 1800 m. Many avalanches failed on the December 27th Surface Hoar and one avalanche on a north/northeast facing slope at 1800 m involved the mid November facets.

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.

Snowpack Summary

The storm of the last days brought 20 to 50 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 which have been active as recently as Monday. 

The base of the snowpack is also weak in parts of the region where it consists of sugary faceted snow around a melt-freeze crust. 

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid freshly wind loaded terrain features.
  • Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely

Expected Size

1 - 2

20 to 50 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 from south to north 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 - 3

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 15th, 2020 5:00PM