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Avalanche Forecast

Archived

Jan 18th, 2017–Jan 19th, 2017

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

Regions

Kootenay Boundary.

Heavy loading from snow and wind is driving avalanche danger up.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

THURSDAY: Flurries, accumulations 5-10cm, strong southwest winds, freezing level around 1300m.FRIDAY: Mainly cloudy with the possibility of isolated flurries, light south wind and freezing level around 1300m.SATURDAY: Mainly cloudy with the possibility of isolated flurries, light south wind and freezing level dropping to around 1000m.More details can be found on the Mountain Weather Forecast.

Avalanche Summary

There were generally no new avalanches reported on Tuesday except for a recent Size 2.5 natural wind slab avalanche on a west facing alpine slope, which was likely triggered by strong southerly winds loading surface hoar and facets. Expect continued natural wind and storm slab avalanche activity with heavy loading from snow and wind, and lingering human-triggered avalanche potential for the forecast period. Also, expect deeper persistent weaknesses to become more reactive with continued snow and wind-loading and warm temperatures.

Snowpack Summary

By Wednesday morning 15-25 cm of fresh snow had fallen across the region accompanied by moderate to strong southerly winds. This has resulted in touchy storm and wind slabs bonding poorly to the previous snow surface that includes facets and large surface hoar on sheltered slopes and/or a sun crust on steep sun-exposed aspects, as well as wind-affected surfaces (e.g. hard wind slab, sastrugi, scoured crust, etc.) in exposed areas. The mid-December surface hoar/ facet layer is now likely down 50-90 cm and may become reactive again with continued loading and warming. In thin rocky areas, particularly in the Rossland range, recent reports include easy sudden collapse snowpack test results on facets down 120-150 cm near the ground. This deep persistent weakness may also become reactive with continued loading and warming.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.