Avalanche Forecast

Issued: Mar 1st, 2014 8:13AM

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

rbuhler, Avalanche Canada

Kootenay Boundary.

We are entering a 'low probability/high consequence' phase with a tricky persistent weak layer. Check out this blog post on difficult decision making and current conditions.Avoid large, unsupported slopes, especially on north aspects.

Summary

Confidence

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

Weather Forecast

A low pressure system moves onto the coast Saturday night and should reach the southern interior by Sunday afternoon. Light flurries and rising temperatures are expected for Monday and Tuesday.Sunday: Light snowfall in the morning, increasing in the afternoon, 6-12cm, treeline temperature around -12C, ridgetop winds 30-50 km/h SWSun. Night/Monday: Snowfall 5-10cm, freezing level around 800m, ridgetop winds 30-50 km/h SWTuesday: Flurries 2-5cm, freezing level around 1300m, ridgetop winds 20-40 km/h SW

Avalanche Summary

On Friday, a size 1.5 skier accidental avalanche was reported. It released at a depth of 30-45cm.On Thursday, two skier accidental avalanches were reported in the KB. These were size 1.5 and 2. The deeper released down 70cm. Also reported were three remotely triggered avalanches up to size 2. The furthest away trigger was 40m. Two natural avalanches were reported up to size 2.5 and were likely triggered by the sun.

Snowpack Summary

The primary concern is a persistent slab (typical thickness 50-90cm) 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. Recent test results are suggesting that the layer is still easy to trigger in some areas but may becoming harder to trigger in other areas. We are still receiving isolated reports of large settlements or whumpfing which suggests the layer still has the potential for large propagations. In many areas the layer has the potential to produce large, destructive avalanches. The phase we are now entering is referred to a 'low probability/high consequence' problem. Continue to use conservative terrain choices until you are sure the layer is no longer unstable in your local area. Strong forecast winds from the SW are expected to create touchy new wind slabs on leeward slopes and cross-loaded features. On south aspects, a sun crust has formed on the surface. New surface hoar formation up to 10mm and near-surface faceting have been observed. The new storm snow will overlie these layers.

Problems

Persistent Slabs

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Wind Slabs

Recent strong winds plus more strong wind in the forecast will continue to load leeward and cross-loaded features. Expect these winds slabs to increase in size as new snow accumulates on Sunday.

Caution in lee and cross-loaded terrain near ridge crests.>Be cautious as you transition into wind affected terrain.>Stay well back from cornices.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 2nd, 2014 2:00PM