Avalanche Forecast

Issued: Feb 13th, 2013 9:30AM

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

triley, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Thursday

Weather Forecast

Overnight and Thursday: Mostly clear with cold temperatures overnight and nil precipitation. Strong Westerly winds are expected to decrease to moderate Northwesterly by morning. Freezing levels down to the valley bottom overnight, and then rising up to about 1300 metres during the day.Friday:Moderate West winds with Alpine temperatures around -5.0 and freezing levels rising to around 1200 metres. Expect broken skies and periods of strong solar radiation. Some high cloud may move into the region by the afternoon.Saturday: The ridge of high pressure is expected to flatten and move off to the East. An upper trough is expected to bring light-moderate snow falls to the region by the afternoon.

Avalanche Summary

Skiers triggered avalanches accidentally up to size 2.0 at treeline in the Selkirks that released down about 25 cms in a layer of new snow, or on a recently buried surface hoar layer. These avalanches were on a North aspect and ran about 200 metres. There were also a couple of natural avalanches up to size 2.0 reported along the highway corridor.

Snowpack Summary

There is a new soft slab developing above the recent surfaces that consists of wind slab in exposed alpine terrain, a sun crust on solar aspects, and surface hoar and/or facets on shady slopes. Below this 20-40 cm of settled storm snow sits on a surface hoar and sun crust layer that developed at the beginning of February. This layer continues to be reactive to rider triggers. Deeper down (between 40-80 cm) sits an old sun crust and well preserved surface hoar that was buried on January 23rd. This persistent slab has been reactive and easily triggered over the past few days, especially from solar aspects and at treeline and below treeline over steeper convex slopes. During recent snowpack testing this layer has shown moderate compression results with sudden planar to resistent planar characteristics. This layer is getting stronger over time and less likely to trigger, but if triggered it will still produce a significant avalanche. The mid-pack is generally well settled and strong.

Problems

Wind Slabs

Wind slabs exist on lee slopes and behind terrain features like ribs and ridges. Be cautious in steep unsupported terrain near ridge top.

Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Storm Slabs

A new soft slab is developing above the recent buried crusts, wind slabs, and weak surface hoar crystals. This new slab may be very easy to trigger on steep rolls and unsupported terrain features.

The new snow will require several days to settle and stabilize.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Persistent slabs are 40-80 cm thick and continue to be reactive above variable sliding surfaces comprising of surface hoar, crusts and facets. They may be triggered by the weight of a skier or a machine.

Avoid open slopes and convex rolls where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Feb 14th, 2013 2:00PM