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Avalanche Forecast

Archived

Jan 13th, 2020–Jan 14th, 2020

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

Regions

North Columbia.

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

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

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.

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.