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Avalanche Forecast

Archived

Feb 21st, 2023–Feb 22nd, 2023

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 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.

Regions

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

Up to 30 cm of recent snow and wind have formed reactive storm slabs at all elevations. The recent snow is sitting on a weak layer of surface hoar in sheltered locations and a suncrust on steep south facing slopes.

Choose conservative terrain and watch for clues of instability.

Confidence

Moderate

Avalanche Summary

Several naturally triggered storm slab avalanches up to size 2 were reported on Monday.

Recently formed storm slabs will likely remain reactive to human triggers; especially in open areas where the wind has stiffened the snow.

Snowpack Summary

Up to 30 cm of recent snow and southwest to northwesterly wind have formed reactive storm slabs at all elevations. The recent snow is sitting on a weak layer of surface hoar in sheltered locations and a suncrust on steep south facing slopes. These weak layers may cause the storm slabs to continue to be reactive to human triggers in many locations.

A slightly older layer of large surface hoar may be found down roughly 50-70 cm below the old snow surface.

The middle of the snowpack is generally well consolidated and stiff but does contain some old persistent weak layers. These layers have not produced avalanches in quite a long time and are not currently a concern unlike neighboring regions to the north, but could wake up with significant storm loading or warming.

The lower snowpack consists of a layer of weak, sugary crystals that is slowly gaining strength and doesn't currently appear to present the same problem as neighboring regions to the north and east. However, we continue to track the layer and watch for any signs that it might wake up and produce very large avalanches.

Weather Summary

Tuesday night

Cloudy / Light, east ridgetop wind / Low temperature at treeline around -22 C.

Wednesday

Mix of sun and cloud / Light, southeast ridgetop wind / High temperature at treeline around -12 C.

Thursday

Sunny / Strong, east ridgetop wind / High temperature at treeline around -18 C.

Friday

Sunny / Strong, west ridgetop wind / High temperature at treeline around -12 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Choose conservative terrain and watch for clues of instability.
  • Use small low consequence slopes to test the bond of the new snow.

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.