Avalanche Forecast Kootenay Boundary

Tuesday 5th February 2019

Avalanche Danger Ratings Tue 5th Feb 4:23PM Danger Ratings Alpine: Moderate Danger Ratings Treeline: Moderate Danger Ratings Below Treeline: Moderate Persistent Slabs Persistent Slabs Wind Slabs Wind Slabs

Avalanche Canada Forecaster: swerner

Date Issued:

Valid Until:

Persistent slab problems are not obvious and tricky to manage. This problem may be found in unsuspecting locations at treeline and below and can catch you by surprise. Even a small avalanche in the trees can be consequential.

Confidence

High - The weather pattern is stable

Weather Forecast

The arctic ridge will continue to bring cold, dry air and northerly winds to the Kootenay Boundary tomorrow. Thursday will see a slight change when the low slides south bringing cloudy skies and some precipitation. Wednesday: Sunny with some cloudy periods. Treeline temperatures near -13 with light ridgetop winds from the North.Thursday: Cloudy with sunny periods. Treeline temperatures near -10 with light ridgetop winds from the North and freezing levels valley bottom.Friday: Cloudy with isolated flurries. Treeline temperatures near -10 with light ridgetop winds from the East.

Avalanche Summary

On Monday, reports indicated that the recent storm snow is reactive to human triggers up to size 2 on northerly aspects around 2100 m. The storm slabs were reportedly failing on most previous surface hoar interface down 20-30 cm which was buried February 1st. Several loose dry avalanches up to size 2 were also reported.

Snowpack Summary

10-30 cm of new snow falling late last week now sits on variety of snow surfaces, including buried wind crust on westerly aspects, crusts on southerly aspects to mountain top and weak feathery surface hoar in sheltered areas at treeline and below. In some places this surface hoar is reported to be sitting on a crust and has been reactive to light loads like people.Digging deeper 40-80 cm below the snow surface, expect to find another crust on south aspects and another layer of predominant feathery surface hoar crystals in sheltered and shaded areas. This deeper layer of surface hoar may be most reactive at treeline elevations on shady aspects. The remainder of the snowpack is generally well-settled and strong. 

Persistent Slabs Persistent Slabs

Likelihood

Possible

Expected Size

1 - 2

There is a layer a layer of weak feathery surface hoar 20-40 cm below the surface and another 40-80 cm down. The former is currently reported to be most reactive, especially where it is sitting on a hard crust.

Caution around sheltered open areas treeline and belowBe aware of the possibility of avalanches triggering on one layer and stepping down to another

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

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Wind Slabs Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Shifting winds have redistributed last week's new snow onto a variety of aspects.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Watch for signs of instability like whumpfing, hollow sounds, and shooting cracks.

Aspects: North, North East, East, South West, West, North West.

Elevations: Alpine, Treeline.

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