Avalanche Forecast Northwest Coastal

Tuesday 5th February 2019

Avalanche Danger Ratings Tue 5th Feb 4:53PM Danger Ratings Alpine: Moderate Danger Ratings Treeline: Moderate Danger Ratings Below Treeline: Low Wind Slabs Wind Slabs

Avalanche Canada Forecaster: cgarritty

Date Issued:

Valid Until:

Shifting winds have blown our storm snow into wind slabs on all aspects in wind-affected areas. Seek out sheltered areas and lower angled slopes for the safest, best skiing and riding.

Confidence

High - The weather pattern is stable

Weather Forecast

Tuesday night: Cloudy with clear periods. Light northwest winds.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow, increasing a bit overnight. Light northwest winds. Alpine high temperatures around -6. Cooler at lower elevations due to a temperature inversion.Thursday: Cloudy with sunny periods and isolated flurries with a trace of new snow. New snow totals of up to 5 cm. Light north winds increasing over the day. Alpine high temperatures around -5. Cooler at lower elevations due to a temperature inversion.Friday: Mainly sunny. Moderate to strong northeast winds. Alpine high temperatures around -15.

Avalanche Summary

Reports from Monday included several small (size 1.5) remote triggered (triggered by a skier at a distance) wind slabs on north aspects at around 1500 metres. Slab depths were 20-25 cm and they had failed on the crust buried beneath our recent storm snow.Wind slabs were also reactive to skier traffic over the weekend, generally producing small avalanches. See here for an example.

Snowpack Summary

Strong northeast winds have redistributed up to 40 cm of recent storm snow, creating wind slabs in lee and cross-loaded terrain features. This snow overlies wind-affected surfaces in the high alpine and a thick melt-freeze crust at and below treeline.In the south of the region, the remainder of the snowpack is well-settled.Around Bear Pass and in the north of the region, there is a weak layer of feathery surface hoar crystals about 50 cm deep. This weak layer is likely most prominent in sheltered and shaded areas. Also in the north, a few weak layers may still exist within the middle and lower half of the snowpack. These include another layer of surface hoar around 70 to 100 cm deep and a weak layer of sugary faceted snow around 200 cm deep.

Wind Slabs Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Strong to extreme northeast winds have redistributed the recent storm snow and created wind slabs in exposed terrain, particularly in cross-loaded and lee terrain features near ridges.

Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.Analyze slopes for patterns of wind loading as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

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