Avalanche Forecast

Issued: Feb 8th, 2013 9:48AM

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.

swerner, Avalanche Canada

South Columbia.

Blue skies, sunshine and fresh snow may tempt you into steeper and bigger terrain. Maintain a diligent approach to terrain selection to best manage the current conditions. If the sun comes out watch solar slopes, they may deteriorate.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

A strong ridge of high pressure builds off the coast allowing a cool, dry NorthWest flow over the region with high diurnal temperature variations. Scattered too few clouds will exist allowing some sunny alpine skies on Saturday with more predominant sunny skies on Sunday. Ridgetop winds will blow steady and light-moderate from the NorthWest. Treeline temperatures will hover near -3 and freezing levels will rise to 1000 m during the afternoon periods.

Avalanche Summary

Natural avalanche activity loose and slab avalanche activity up to size 2 occurred on Thursday. The natural cycle has slowed down significantly, yet the rider triggered avalanches are ongoing. We have continued to receive reports of rider triggered slab avalanches up to size 2 throughout the region. Most of these cases still involving the persistent weak layers below the surface. They snowpack remains touchy to light loads. Avalanche activity may continue through the forecast period, additional concerns being solar radiation as a natural trigger.

Snowpack Summary

New snow (20-40 cm) adds to the recent storm slab which sits on a surface hoar layer and a sun crust layer that developed at the beginning of February. This layer continues to be reactive. 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.Wind slabs persist in the alpine and at treeline. The loading pattern may change due to winds switching from the SouthWest to the NorthWest and form pockets of wind slab in unsuspecting places. At lower elevations a melt-freeze crust has formed due to the recent high freezing levels.The mid-pack is well settled and strong. Watch the duration and intensity of the sun in your local riding area; it may weaken the upper snowpack. Cornices loom and threaten slopes below.

Problems

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 are easily triggered by the weight of a skier or a machine.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a line.>Good group management is essential to manage current conditions safely.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Wind Slabs

Lee slopes and behind terrain features like ribs and ridges are a concern. Changing winds may load unsuspecting aspects. In sheltered areas watch for natural loose sluffing over convex rolls and from steep terrain. Cornices may threaten slopes below.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Valid until: Feb 9th, 2013 2:00PM