Avalanche Forecast

Archived

Mar 17th, 2021–Mar 18th, 2021

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 possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

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.

Regions

Kootenay Boundary.

The danger will be LOW when a thick melt-freeze crust is on the snow surface and increase during the heat of the day as warm air and sun weaken the snow surface. Best to get off steep slopes before they moisten and watch your overhead exposure.

Confidence

High -

Weather Forecast

WEDNESDAY NIGHT: Clear skies, 20 km/h south wind, alpine temperature 0 C, freezing level 2200 m but snow-surface freeze is likely.

THURSDAY: Clear skies in the morning and afternoon cloud, 30 km/h south wind, alpine temperature 1 C, freezing level 2300 m.

FRIDAY: Cloudy with rain switching to snow, accumulation 10 to 20 cm above the rain-snow line, 20 to 40 km/h southwest wind, alpine temperature -3 C, freezing level lowering to 1500 m.

SATURDAY: Mix of sun and cloud, 20 km/h southwest wind, alpine temperature -5 C.

Avalanche Summary

No new avalanches were observed on Wednesday, with the exception of small loose wet avalanches out of steep sun-exposed terrain in the afternoon. Similar activity is possible during this diurnal cycle period.

Snowpack Summary

We are in the midst of a diurnal cycle, where the snow surface will freeze into a melt-freeze crust at night and moisten during daytime heating, particularly on sun-exposed slopes. Dry, settled snow may still exist near the mountain tops on northerly aspects. Cornices are large and always have the potential of failing, particularly during daytime warming.

Deeper in the snowpack, a persistent weak layer from late January is buried around 80 to 150 cm and is composed of a combination of surface hoar, facets, and crusts. We haven't received a report of avalanche activity on this layer since late February. The likelihood of triggering this layer is low during the current diurnal cycle, with a thick melt-freeze crust expecting to form each night.

As always, best to avoid shallow, rocky areas where a weak and faceted snowpack may be found.

Terrain and Travel

A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Extra caution is needed around cornices under the current conditions.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.