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Avalanche Forecast

Archived

Mar 13th, 2023–Mar 14th, 2023

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

15-25 cm new snow and strong south wind have formed reactive storm slabs at all elevations.

Use small low consequence slopes to test the bond of the new snow.

Confidence

High

Avalanche Summary

Explosive control work on southerly aspects at treeline produced numerous storm slabs to size 2 on Monday.

Snowpack Summary

15-25 cm of new snow, strong south winds, and rising freezing levels have formed reactive storm slabs.

This brings recent snow amounts to 40-50 cm which overlies a variety of surfaces. These include surface hoar (3-5 mm) on shady slopes, wind affected surfaces at treeline and above, and sun crust on sunny aspects.

A layer of surface hoar or sun crust (aspect dependent) can be found down 50-70 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

Monday Night

Snow; 10-20 cm / 40 km/h west ridgetop wind / Low temperature at treeline around -8 C / Freezing level valley bottom

Tuesday

Mix of sun and cloud / 20 km/h southwest ridgetop wind / High temperature at treeline around -8 C / Freezing level 1200 m

Wednesday

Mix of sun and cloud / 20 km/h west ridgetop wind / High temperature at treeline around -6 C / Freezing level 1300 m

Thursday

Sunny / 10 km/h south ridgetop wind / High temperature at treeline around -4 C / Freezing level 1500 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • Use small low consequence slopes to test the bond of the new snow.
  • Avoid exposure to slopes that have cornices overhead.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.