Avalanche Forecast

Issued: Feb 15th, 2020 5:00PM

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

Avalanche Canada shorton, Avalanche Canada

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Keep your guard up as you approach avalanche terrain, recent snow has formed unstable slabs.

Summary

Confidence

Moderate - A small change in the upper snowpack could dramatically change avalanche conditions.

Weather Forecast

SATURDAY NIGHT: Light flurries with a trace to 5 cm of new snow, moderate wind from the west, alpine temperatures drop to -10 C.

SUNDAY: A few sunny breaks and light flurries with a trace amounts of new snow, moderate wind from the west, alpine high temperatures around -8 C.

MONDAY: Mix of sun and cloud, light wind from the west, alpine high temperatures around -8 C.

TUESDAY: Sunny with a few clouds, light wind from the northwest, alpine high temperatures around -8 C.

Avalanche Summary

Steady snowfall and wind over the past week has resulted in storm slab and wind slab avalanches. On Friday, a natural cycle of size 1-2 avalanches occurred, primarily in wind affected terrain. Several small (size 1) human triggered slabs were also reported, and one large (size 2.5) wind slab was triggered by a skier on a northeast aspect at 2000 m. This MIN report from the neighbouring Clemina area has a good photo of a recent snowmobile triggered wind slab.

One isolated deep persistent slab avalanche (size 2.5) was reported last weekend. It was 130 cm thick and remotely triggered (from a distance) in a shallow area on an east aspect at 2300 m. A decreasing trend in the number of persistent slab avalanches over the past few weeks suggests these large avalanches are unlikely to trigger under the current conditions.

Snowpack Summary

40-60 cm of snow has fallen over the past week. Up to now it has primarily been a concern on wind-loaded slopes, but as this snow settles into a slab it could become reactive on sheltered slopes too. In some areas this new snow may sit above small surface hoar (in open terrain at treeline), sun crusts (in open south-facing terrain), or a thick rain crust (below 1700 m). Overall there is some uncertainty about where and when recent storm snow may develop into reactive slabs.

The mid and lower snowpack are generally well settled and strong. There are two deeper layers that may be found in isolated locations; 1) an aging surface hoar layer from late December is 100 to 150 cm below the surface on treeline slopes in southern parts of the region, and 2) a facet/crust layer from November found near the ground in shallower snowpack areas. Both of these weak layers have trended towards being unreactive under the current conditions.

Terrain and Travel

  • Start on smaller terrain features and gather information before committing to bigger terrain.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Use caution when approaching steep and rocky terrian.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

Problems

Storm Slabs

An icon showing Storm Slabs

Accumulations of new snow over the past week have already formed reactive slabs in wind affected terrain, and is potentially settling into storm slabs in sheltered terrain as well.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Feb 16th, 2020 5:00PM

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