Avalanche Forecast

Issued: Feb 9th, 2013 8:55AM

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

jfloyer, Avalanche Canada

South Coast.

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 5 cm new snow starting late in the day. Freezing level around 1000 m. Moderate or strong southwesterly winds.

Avalanche Summary

Human triggered avalanches occurred in a few areas outside, but immediately adjacent to this region. The avalanches were triggered on a variety of aspects, but a common theme appears to be the presence of a crust buried 30-40 cm below the surface. Loose wet avalanches were reported in response to solar warming.

Snowpack Summary

Around 30-40cm new snow fell on average during recent storms, which ended on Friday. The Coquihalla area received a little more (up to 65 cm). Consistent southwesterly winds during the storm period redistributed the new snow into windslabs and grew cornices on lee terrain features in the alpine and at treeline. The recently buried surfaces (Feb 3rd interface) are old wind slabs (behind ridges, ribs and on lee slopes) and sun crusts (on south and west facing slopes). In isolated locations, this interface comprises small surface hoar crystals. Down a further 20-50 cm sits a persistent interface comprising of crusts, facets and surface hoar crystals. This layer is now mostly unreactive, with only one size 2 avalanche reported (on Feb 6th) since the end of January. If it were to be triggered again, the most likely spot would be a steep convex roll on a sheltered north aspect slope around treeline. A recent Rutchblock test gave a score of 6 with a partial block release in the Duffey Lake area. The mid and lower snowpack pack layers are generally well settled.

Problems

Storm Slabs

Warm temperatures may 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

Possible - Likely

Expected Size

1 - 5

Loose Wet

When the sun comes out the surface snow will 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