Avalanche Canada shorton, Avalanche Canada

Cariboos Avalanche Forecast

Jan 13th, 2020 5:00PM

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

Triggering wind slab avalanches is possible in open terrain and a buried weak layer could cause large avalanches around treeline.

Summary

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

MONDAY NIGHT: Clear, light wind from the north, alpine temperatures drop to -40 C.

TUESDAY: Sunny, light wind from from various directions, alpine high temperatures around -30 C.

WEDNESDAY: Sunny, light wind from various directions, alpine high temperatures around -28 C.

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

Avalanche Summary

There have been limited field observations recently, but enough to suggest the persistent slab avalanche problem remains a concern. A large persistent slab avalanche was triggered by a rider in the neighbouring Clemina area on Friday (see the MIN report) and riders on Belle Mountain near McBride reported "thunderous" whumpfing in south facing terrain at treeline. Some of these older MIN reports provide helpful photos of slopes where this layer has been a problem (here, here, and here).

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 10-30 cm of soft powder. The main concern is a layer of surface hoar that formed in late December, which is now buried 60-120 cm deep throughout the region. This layer is most likely found on sheltered slopes at and below treeline. Reports suggest the reactivity of layer may be variable, as on some slopes it is well bonded while on other slopes it is still very reactive.

Terrain and Travel

  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Be alert to conditions that change with elevation, aspect and exposure to wind.

Problems

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Possible-Likely

Expected Size

2 - 3

A concerning layer of surface hoar is buried 60-120 cm below the surface and continues to be reactive to human triggering on certain slopes. The challenge is determining which slopes, meaning steep open slopes at lower elevations should be approached with great caution.

Aspects:

All aspects.

Elevations:

Treeline, Below Treeline.

Wind Slabs

An icon showing Wind Slabs

Likelihood

Likely

Expected Size

1 - 2

Watch for areas where the low density snow has been blown into unstable wind slabs. Strong outflow winds from the north may have produced wind slabs in unusual places.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

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