Avalanche Forecast

Issued: Jan 23rd, 2018 4:43PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

jsmith, Avalanche Canada

Kootenay Boundary.

Avalanche hazard is forecast to increase throughout the day on Wednesday. Avoid all avalanche terrain during periods of rapid loading from snow or wind.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Tuesday Night: 10-15cm of new snow / Moderate to strong southwesterly ridgetop winds / Freezing level around 700m.Wednesday: 15-20 cm of new snow / Moderate to strong southerly ridgetop winds / Freezing level rising to around 1400m.Thursday: Mostly cloudy with isolated flurries / Light to moderate southerly ridgetop winds / Freezing level dropping to around 900m.Friday: Mostly cloudy with isolated flurries / Light to moderate southwesterly ridgetop winds / Freezing level dropping to around 500m.

Avalanche Summary

On Monday, numerous explosive triggered, size 2 storm slab avalanches were reported near Whitewater and Kootenay Pass. Looking forward, forecast snow and wind will promote ongoing storm slab avalanche activity, especially in higher elevation, lee terrain.

Snowpack Summary

Since last Friday, 15-30cm of new snow fell with the greatest accumulations occurring in the Kootenay Pass area. Moderate to locally strong southwest winds have redistributed the new snow into reactive storm slabs in exposed lee terrain.Approximately 30 - 50 cm of storm snow now covers the most recent crust/surface hoar layer that was buried mid-January. This crust can be found on solar aspects while surface hoar has been buried on shaded aspects above 1600m. Below this layer lies a second crust/surface hoar interface buried early-January that is now 50-90 cm below the surface. The mid-December surface hoar layer is buried 100-140 cm below the surface. This spooky layer still produces "sudden" test results and is most pronounced at treeline, but is also present below treeline . Two laminated crusts created by rain events in late November lay just below the mid-December interface, and may co-exist with facets.

Problems

Storm Slabs

Forecast new snow, wind, and warming are expected to create very touchy storm slabs during the day on Wednesday. If triggered, these slabs have the potential to step down to one or more deeper weak layers buried in the snowpack.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.Be cautious when transitioning into wind effected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Persistent Slabs

The snowpack is complex and has produced very large and destructive avalanches on up to four separate weak layers buried 50 to 140cm below the surface. A conservative approach and moderate-angled, simple terrain are good choices.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Be mindful that deep instabilities are still present and have produced recent large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Jan 24th, 2018 2:00PM