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Avalanche Forecast

Archived

Jan 13th, 2020–Jan 14th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Cariboos.

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

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

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.