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Avalanche Forecast

Archived

Mar 16th, 2023–Mar 17th, 2023

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.

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, South Okanagan, Ymir, Moyie.

Warming temperatures and solar input will increase the avalanche hazard during the warmest part of the day.

Seek out northerly slopes with low overhead hazards for the best and safest riding in the afternoons.

Confidence

High

Avalanche Summary

On Wednesday there were two storm slab avalanches that were accidentally triggered by riders. These were on east and north aspects at treeline elevations. The layer that they ran on was a surface hoar/crust combo that the most recent storm snow buried. In both instances, the point where the avalanche was triggered was on a convex roll.

Snowpack Summary

The storm slabs, 30 to 50 cm thick, overlie a variety of surfaces, which include surface hoar, 3 to 5 mm, on shady slopes at all elevations, wind-affected surfaces at treeline and above, and sun crust on sunny aspects. Storm snow was accompanied by strong south winds. Expect wind slab formation at higher elevations. Solar aspects and lower elevations will be affected by day time warmer and nighttime freezing. Expect a crust in the morning and moist snow in the afternoon.

A layer of surface hoar or sun crust, aspect dependent, that was formed in mid-February can be found down 80 to 110 cm.

The lower snowpack includes a layer of weak sugary facets near the ground. These facets are slowly gaining strength and no recent avalanches have been reported on this layer. However, we continue to track the layer and watch for any signs of it becoming active.

Weather Summary

Thursday Night

Clear, no accumulation, winds southeast 10 to 15 km/h, treeline temperatures -5 to 0 °C .

Friday

Sunny, no accumulation, winds southerly 10 to 15 km/h, treeline temperatures -3 to 2 °C with freezing levels getting up to 1800 m.

Saturday

Mostly sunny with some cloudy periods, no accumulation, winds south 10 to 15 km/h, freezing levels possibly getting up to 1900 m.

Sunday

Sunny, no accumulation, winds south 10 to 15 km/h, freezing levels to 2000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Make conservative terrain choices and avoid overhead hazard.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.

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.

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.