Avalanche Forecast

Issued: Mar 5th, 2016 8:25AM

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

triley, Avalanche Canada

South Columbia.

Forecast new snow and wind will continue to develop storm slabs over surface hoar and crusts. Expect remote triggering and wide fracture propagations resulting in large avalanches. Conservative terrain selection is essential.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Cloud developing Saturday evening, and then strong southerly winds with 5-10 cm of new snow overnight. The freezing level should dip down to 1300 metres overnight and then climb up to 1800 metres on Sunday. Another 10-15 cm of new snow during the day Sunday combined with strong southwest winds. Freezing levels dropping to valley bottoms by Monday morning. Mostly sunny on Monday with strong solar radiation and freezing levels around 1500 metres. Cloudy with light precipitation on Tuesday.

Avalanche Summary

Skier accidental, skier remote triggered, and natural avalanches up to size 2.5 continued to be reported on Friday. Most of these avalanches were releasing in the storm snow, or at the storm snow/surface hoar interface. On Thursday, natural avalanches up to size 2.0 were reported as well as several remotely triggered slab avalanches up to size 2.0. These slides occurred on all aspects, at all elevations, and were generally 40-60 cm deep.

Snowpack Summary

Variable amounts of new snow and wind have continued to develop storm slabs 40-60 cm thick that are bonding poorly to a crust on previously sun-exposed slopes and surface hoar (February 27th) on shady and sheltered slopes. Thicker and touchier wind slabs are lurking throughout exposed terrain at and above treeline. A weak layer of surface hoar and/or a sun crust buried February 21 is now close to a metre below the surface. Where it exists, this layer may become reactive to human triggers as the overlying slab develops. The surface hoar and/or crust layer buried February 10 is likely down over a metre. This layer was less reactive over the past week with cooler temperatures, but remains a concern for large triggers like cornice falls or a smaller avalanches stepping down. Cornices are large and potentially weak and should be avoided where possible.

Problems

Storm Slabs

Storm slabs are expected to continue to develop with forecast new snow and wind. Storm slabs may be sitting on a crust or crust/surface hoar combination down 40-60 cm that is easy to trigger and may result in wide fracture propagations.

Minimize exposure during periods of heavy loading from new snow, wind.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

The February 10th buried surface hoar layer may be down about one metre in most areas. Heavy loading from new snow and wind, as well as high freezing levels may increase the likelihood of triggering this deeply buried weak layer.

Caution around convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Cornices

Cornices are large and fragile. Continued loading from new snow and wind may result in natural cornice falls.

Cornices become weak with daytime heating. >Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 6th, 2016 2:00PM