Avalanche Canada shorton, Avalanche Canada

North Columbia Avalanche Forecast

Jan 13th, 2020 5:00PM

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

Triggering wind slab avalanches is possible in open terrain and in certain parts of the region a buried weak layer could cause large avalanches.

Summary

Confidence

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

Weather Forecast

MONDAY NIGHT: Clear, light wind from the west, alpine temperatures drop to -35 C.

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

WEDNESDAY: Mostly sunny, light wind from the southwest, alpine high temperatures around -20 C.

THURSDAY: Mix of sun and cloud, light wind from the south, alpine high temperatures around -20 C.

Avalanche Summary

Over the weekend accumulations of low density snow resulted in several small (size 1) wind slab, storm slab, and dry loose avalanches and a few larger (size 2) wind slabs.

There have also been ongoing reports of large persistent slab avalanches being reactive to human triggering over the past week. These avalanches have been reported in the Selkirks and the northern tip of the Monashees (near Blue River and Valemount). The avalanches have failed on a surface hoar layer buried roughly 100 cm below the surface, and in terrain between elevations of 1200 to 2100 m on north and east aspects. Examples include a large (size 3) avalanche that was remotely triggered on Saturday and a large (size 2.5) avalanche triggered by a snowmobile in Clemina on Friday (see photo in this MIN report). This pattern of activity suggests this problem remains a serious concern in parts of the North Columbias.

Snowpack Summary

As cold arctic air settles over the region expect wind slabs in unusual places due to recent valley winds from the north, while sheltered areas still have 20-40 cm of soft powder. A layer of surface hoar is now buried 80-120 cm below the surface and continues to be a concern in the Selkriks and the northern end of the Monashees. 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.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Don't let the desire for deep powder pull you into high consequence terrain.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Monitor changes in surface conditions as you travel through terrain. It may have blown into unstable wind slabs in open terrain or run as dry loose avalanches in steep terrain.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3

A concerning layer of surface hoar has been reactive to human triggers in the Selkirks and northern Monashees (around Blue River and Valemount). This layer is buried 80-120 cm below the surface, meaning triggering this layer would result in a large avalanche. Steep open slopes at and below treeline should be approached cautiously.

Aspects:

All aspects.

Elevations:

Treeline, Below Treeline.

Valid until: Jan 14th, 2020 5:00PM