Avalanche Forecast

Issued: Feb 26th, 2014 8:08AM

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

rbuhler, Avalanche Canada

Kootenay Boundary.

Use increased caution on sunny, south-facing slopes. Hazard will increase during the afternoon warming.

Summary

Confidence

Fair

Weather Forecast

High pressure conditions are expected for Thursday before a weak system from the southwest affects the region Thursday night and Friday. On Friday night, cold arctic air will push into the region and will dominate on Saturday.Thursday: A mix of sun and cloud, temperature inversion conditions likely, ridgetop winds 20-30 W-NWThurs. night/Friday: Mostly cloudy, snow flurries 2-5cm, treeline temperature around -5C, ridgetop winds 20-30 W-NW in the morning, decreasing in the afternoonSaturday: Mostly sunny, treeline temperature around -15C, ridgetop winds light NE

Avalanche Summary

Skier triggered avalanches are continuing to surprise people up to size 2, while explosive control mission also showed several slab avalanches up to size 2.5. The deepest avalanche reported on Tuesday released down 120cm.On Sunday, a skier triggered size 2.5 was reported. Party of three with two involved. Sadly RCMP reported one fatality and the other suffered serious injuries. The crown was near 100 cm deep and released near ridgetop in storm snow and then stepping down to the persistent weak interface and running a far distance through the trees. Check out the Forcaster Blog! It shows a photo of a remote triggered size 3 last Friday in the southern part of the Kootenay-Boundary.

Snowpack Summary

The primary concern is an approximately 1m thick slab from the last series of storms that is sitting on a stubborn persistent weak layer consisting of facets, surface hoar, melt-freeze crusts, or any combination of these. This weak layer is widespread at all elevations and aspects. We have been receiving reports of whumpfing and easy sudden planar snowpack test results on this layer. The persistent slab continues to settle and become more cohesive allowing for larger fracture propagations and remote triggering from up to 200m away. This persistent weak layer is expected to be a concern for longer than we are used to. Variable winds from the southwest through north have created touchy wind slabs on leeward slopes and cross-loaded features. In wind-loaded areas, slabs up to 2m thick may overly the persistent weak layer.With the current sunny and warm inversion conditions, solar aspects will likely see moist snow during the day, then forming a crust overnight. New surface hoar formation 5-10mm has been observed.

Problems

Persistent Slabs

Expect the deeply buried weak layers to continue to produce large and destructive avalanches. Slopes are primed for human triggering and remain a concern on all aspects and elevations.

Use conservative route selection and resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>Remote triggering is a big concern, be aware of the potential for wide propagations and large, destructive avalanches at all elevations.>Avoid areas with overhead hazard, especially on solar aspects.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Wind Slabs

Wind has transported snow and built fresh, touchy wind slabs. Be aware of weak cornices looming over slopes. If they fail, they will likely trigger a large slab avalanche on the slope below.

Caution in lee and cross-loaded terrain near ridge crests.>Avoid freshly wind loaded features.>Extra caution needed around cornices with current conditions.>

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Feb 27th, 2014 2:00PM