Avalanche Forecast

Issued: Feb 9th, 2013 9:54AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs, Cornices and Loose Wet.

jfloyer, Avalanche Canada

Sea To Sky.

Summary

Confidence

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

Weather Forecast

Synopsis: Initially, a ridge of high pressure will bring dry, sunny weather for Sunday with increasing cloud through Monday. On Tuesday afternoon, a Pacific frontal system will bring precipitation to the region.Sunday: Dry and mostly sunny. Freezing level going as high as 2300 m. Light northerly winds.Monday: Should stay dry with cloud cover increasing through the day. Freezing level dropping to around 1000 m. Generally light winds, but westerly gusts to 60km/h at ridgetop are possible.Tuesday: Up to 10 cm new snow starting late in the day. Freezing level around 1200 m. Moderate or strong southwesterly winds.

Avalanche Summary

There are important differences in avalanche activity depending on whether you are in the north of the region or in the south. For the south, large avalanches ran during the recent storm, but activity appears to have subsided relatively quickly due to warm temperature and higher snowfall amounts. In the north, where the lower snow amounts have left weak layers more intact, reports continue of rider-triggered and remote-triggered avalanches up to size 2.5. These appear to be failing particularly where a crust lies buried under the upper slab and have been reported from treeline and alpine elevations.

Snowpack Summary

The most recent storm, which ended Friday morning, brought widely varying snowfall amounts to the region, with 30cm in the north end and up to 90cm in the south. Consistent southerly winds during the storm period built windslabs in lee terrain and helped grow cornices.Recently buried surfaces (the Feb. 3 interface) include old windslabs and sun crusts. The new snow is bonding reasonably well at this interface in most locations with the highest concern being the bond to crusts on south and west facing terrain. The January 23rd interface (crusts, facets and surface hoar crystals) lingers in isolated locations. This layer seems to be rounding and bonding under current conditions, but we have reports of a recent size 2.0 releasing on this layer. The mid pack is generally well settled with the average snowpack depth at treeline around 180 cm.

Problems

Storm Slabs

Warm temperatures will likely promote the upper slab to fail, particularly on steep terrain where there is a buried crust. Wind slabs remain in exposed lee areas also.

Avoid steep Southerly aspects.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Cornices

Cornices have grown significantly with the recent storm and may be more prone to failure with daytime heating/solar radiation.

Do not travel on slopes that are exposed to cornices overhead.>Stay well back from cornices.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Likely

Expected Size

2 - 4

Loose Wet

When the sun comes out, expect the surface snow on south facing terrain to de-stabilize.

Watch for wet loose or slab activity with forecast warm temperatures.>

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 3

Valid until: Feb 10th, 2013 2:00PM