Avalanche Forecast

Issued: Jan 30th, 2012 9:12AM

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

swerner, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Tuesday: Snow amounts near 10cms. Ridgetop winds 30-35km/hr from the West. Freezing levels near 900m. Treeline temperatures -4. Wednesday: Snow amounts 5-10cms. Ridgetop winds 20-35km/hr from the West, switching Northerly in the afternoon. Freezing levels near 1000m. Thursday: Generally dry. Warmer air elevating freezing levels up to 1500m. Valley cloud may persist with possible inversions.

Avalanche Summary

Numerous reports of natural avalanche activity occurred over the weekend ranging in sizes from small-large (size 1-3's). All were reported as slab avalanches initiating from 1200m-2700m, mainly on N-NE aspects, but some operations seeing all aspects active. I suspect natural activity may die down early this week, but rider triggered avalanches are likely. It may take a few days for the storm snow to settle out and start to stabilize.

Snowpack Summary

Over the weekend the region received snow amounts near 40-60cms. The initial half of the storm snow came in dryer then the second half, leaving us with upside-down conditions (heavier snow overlying lighter snow). Storm slabs have been forming at all elevations. Wind slabs are developed on lee slopes in the alpine and at treeline from the randy SW winds. Monday morning the winds switched from SW to NW. This may create wind slabs on reverse slopes; I suspect this to be short lived but noted. Buried below the storm snow seems to be a fairly settled mid-pack, with a couple lingering layers.We continue to monitor the old storm snow which rests on dry cold snow formed during an Arctic Outbreak. A few days ago a Rutschblock test in the north showed a result of RB6, MB down 90 on this layer. In the south a CTE test produced a failure down 70 at this interface. We may see some limited activity out of this layer, but I think it may be on its way out.This storm snow will also act as a test for the Jan. 13th SH/FC layer. If it doesn't perform by the early parts of the week, then I think it may be time to call it dormant.Deep down in the pack the mid December layer has gained a lot of strength and I don't think we'll see any action from this layer until the spring. The average snowpack depth at 1700m is 2-3 m.

Problems

Wind Slabs

Wind slabs 50 - 100 cm in depth are possible as strong winds accompanied the weekend storm. With this much loading I'd give wind exposed terrain a miss as it will need another day to adjust to the new load.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Storm Slabs

Up to 60cms of storm snow fell over the weekend forming storm slabs at all elevations. These have been reactive. It may take a few days for the snow to settle out. You're most likely to trigger a storm slab in steep and/or unsupported/convex terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Cornices

Large cornices have formed. You should give them a wide berth whether traveling near them or far below them. Failing cornices have the potential to trigger large avalanches on the slope below.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Jan 31st, 2012 8:00AM