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Avalanche Forecast

Archived

Jan 11th, 2020–Jan 12th, 2020

Alpine
Natural avalanches possible, human triggered probable.
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, human triggered possible.

Regions

North Columbia.

Watch for areas where the new snow feels stiff or slabby and remain cautious of open slopes and convex rolls.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

SATURDAY NIGHT: Mostly cloudy with light isolated flurries, light to moderate wind from the west, alpine temperatures drop to -15 C.

SUNDAY: Scattered flurries with 5-15 cm of low density snow, light wind, alpine high temperatures around -12 C.

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

TUESDAY: Mostly sunny, light wind from the west, alpine high temperatures around -22 C.

Avalanche Summary

Recent accumulations of low density snow resulted in several small (size 1) slab and dry loose avalanches on Friday. There were also a few reports of human triggered persistent slab avalanches that released on a 100 cm deep surface hoar layer on north and east aspects (including this MIN report from Clemina). There have been numerous reports of similar persistent slab avalanches over the past week, suggesting the buried surface hoar layer remains reactive to human triggering in the North Columbias, especially between 1200 and 2100 m.

Snowpack Summary

Low density snow continues to accumulate, with 20-40 cm of fresh light snow on the surface. Cold temperatures and light wind should preserve this snow with the exception of some higher elevation terrain where isolated wind slabs could exist. 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 and/or sparsely treed slopes cautiously.
  • Be especially cautious as you transition into wind affected terrain.

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.