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Avalanche Forecast

Archived

Feb 26th, 2023–Feb 27th, 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.

Dial back your terrain choices if you are finding more than 20 cm of new snow. Use extra caution as you transition into wind affected areas where deeper, cohesive storm slabs are reactive to human triggering.

Confidence

Moderate

Avalanche Summary

On Saturday, storm slabs were reactive to skier traffic to size 2. A skier accidental size 1.5, storm slab avalanche was also reported at treeline.

This week, slabs were reactive to natural and human triggers to size 2, and explosives control to size 3. Activity occurred on all aspects from variable wind loading. Most avalanches occurred within the storm snow or wind loaded features, while a few failed on the buried surface hoar layer.

Please post your field observations and photos on the Mountain Information Network. The information is beneficial to forecasters and fellow backcountry users.

Snowpack Summary

10-20 cm of storm snow, overlies heavily wind affected surfaces at all elevations (Check out this MIN for wind effect photos). Expect deeper deposits on north and east facing slopes, from southwest winds.

A layer of surface hoar can be found on shaded slopes, and a sun crust on sun affected slopes buried 30-60 cm deep. Otherwise, the snowpack is generally well consolidated and bonding.

The lower snowpack includes a layer of weak sugary crystals near the ground. These facets are slowly gaining strength and have not produced recent avalanche activity. We continue to track the layer and watch for any signs that it could wake up and produce very large avalanches.

Weather Summary

Sunday Night

Cloudy with snowfall tapering early evening, 2-5 cm expected. Southerly ridgetop winds 25 km/h. Freezing levels drop to the valley bottom. Alpine high of -8°C.

Monday

Partly cloudy with isolated flurries, trace accumulation. Southerly ridgetop winds 25 km/h. Freezing levels valley bottom, alpine high of -7 °C. Possible flurries.

Tuesday

Cloudy with isolated flurries, 2-5 cm. Southerly ridgetop winds 25 km/h. Freezing levels valley bottom, alpine high of -7 °C.

Wednesday

Mix of sun and cloud. Westerly ridgetop winds 25 km/h. Alpine high of -5 °C. Freezing levels 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.

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.