Avalanche Canada shorton, Avalanche Canada

North Columbia Avalanche Forecast

Jan 12th, 2020 5:00PM

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

Use extra caution around steep and open slopes. A buried weak layer has potential to produce large avalanches at lower elevations, while wind slabs exist at higher elevations.

Summary

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

SUNDAY NIGHT: Isolated flurries with up to 5 cm of low density snow, strong wind from the north in the valleys and moderate wind in the alpine, alpine temperatures drop to -25 C.

MONDAY: Mix of sun and cloud, light wind from the west, alpine high temperatures around -22 C.

TUESDAY: Mostly sunny, light wind from the southwest, alpine high temperatures around -25 C.

WEDNESDAY: Sunny, light wind from the southwest, alpine high temperatures around -25 C.

Avalanche Summary

Over the weekend accumulations of low density snow resulted in several small slab and dry loose avalanches (size 1). There have also been ongoing reports of large persistent slab avalanches being reactive to human triggering over the past week. These avalanches have failed on a surface hoar layer roughly 100 cm below the surface and found between elevations of 1200 to 2100 m (and primarily on north and east aspects). Most recently, a large size 3 avalanche on this layer was remotely triggered in the Selkirks on Saturday. Another large persistent slab avalanche was triggered by a snowmobiler in Clemina on Friday (see the photo in this MIN report). The recent pattern of activity suggests this problem remains a serious concern in the North Columbias.

Snowpack Summary

Low density snow continues to accumulate, with 20-40 cm of fresh light snow on the surface. A short lived period of strong northerly wind on Sunday night could transport snow and form wind slabs in unusual places. Otherwise cold temperatures and easing winds should preserve low density snow in most places. A layer of surface hoar is now buried 80-120 cm below the surface and continues to be a concern across the region. A facet/crust layer from late November lingers near the bottom of the snowpack and has occasionally been reactive in isolated shallow snowpack areas.

Terrain and Travel

  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Choose slopes that are well supported and have limited consequence.

Problems

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible-Likely

Expected Size

2 - 2.5

A weak layer of surface hoar is buried 80-120 cm deep and has produced numerous human triggered avalanches over the past week. Steep open slopes at and below treeline should be approached cautiously.

Aspects:

All aspects.

Elevations:

Treeline, Below Treeline.

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Monitor changes in the most recent low density snow. It may be blown into unstable slabs in wind affected terrain or run as small dry loose avalanches in steep terrain.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

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