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Avalanche Forecast

Archived

Mar 1st, 2025–Mar 2nd, 2025

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

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Crawford.

Dramatic warming has contributed to a steady pattern of destructive persistent slab activity and Sunday promises more. It'll be a great day to soak up the heat in low-consequence terrain.

Confidence

Moderate

Avalanche Summary

Explosives control in Ymir Bowl produced a size 3 persistent slab on a steep, northwest-facing feature at 2100 m on Friday. It's consistent with a pattern of recent persistent slabs in the size 2 to 3.5 range, mainly running on the late January crust and featuring 60 - 80 cm crowns. See the size 3.5 below. Heightened persistent slab activity will be concern for the duration of the warmup.

Many wet loose and wet slabs were also controlled or ran naturally in Kootenay Pass Friday.

Snowpack Summary

A melt-freeze crust or moist snow likely makes up the surface on all but high elevation north aspects. High overnight freezing levels mean crust recovery may be weak. This crust tops the upper part of 30 to 50 cm of settling recent snow, which is wind affected at higher elevations and may overlie faceted snow or surface hoar where sheltered.

Two other key weak layers are present in the mid snowpack: a surface hoar or thin crust from mid-February buried 40-60 cm deep, and faceted snow/surface hoar/crust from late January buried 60-90 cm deep. These layers have been active during recent storms and warm temperatures and remain in question while warming continues to test the snowpack.

Weather Summary

Saturday Night

Clear. 5 to 15 km/h south ridgetop wind. Freezing level falling from 3100 m to 2600 m.

Sunday

Mainly sunny with cloud increasing in the afternoon. 5 to 20 km/h variable ridgetop wind, shifting northwest and increasing. Freezing level falling to 2400 m. Treeline temperature 6 °C.

Monday

Partly cloudy with scattered flurries increasing. 20 to 30 km/h north ridgetop wind. Freezing level to 1700 m. Treeline temperature around 0 °C.

Tuesday

Partly cloudy with 5 - 10 cm of new snow above 1700 m from overnight flurries.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for large, destructive avalanches due to deeply buried weak layers.
  • Use careful route-finding and stick to moderate angled slopes with low consequences.
  • Avoid exposure to overhead hazards when solar radiation is strong.

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.

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.