Avalanche Forecast

Issued: Jan 7th, 2012 9:40AM

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

Avalanche Canada triley, Avalanche Canada

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

The Pacific system that hit the north coast today is moving inland this evening. Very strong winds on the coast are expected to diminish to about 70 km/hr from the southwest by the time they reach the Cariboos and the Monashees. I expect that there will be about 15-20 cm of new snow by Sunday morning. The freezing level is forecast to rise to about 1500 metres on Sunday morning, and then lower back to 1000 metres by Sunday evening. Another pulse of snow is forecast for Sunday evening that looks like it will bring another 10-15 cm combined with moderate southwest winds. The snow should end during the day on Monday after leaving about 5cm. Cooler clear weather is expected Monday night and should continue for Tuesday.

Avalanche Summary

A natural cornice failure from Friday on an east aspect at 2600 metres caused an avalanche size 2.5

Snowpack Summary

Strong southwest winds and moderate to heavy precipitation has begun to build new windslabs in the alpine and at treeline. The recent snowfalls add up to about 60-80 cm of "storm" snow that has been available for wind transport. The warm temperatures and high freezing levels caused the wind transported snow to become a well consolidated slab. There are two rain crusts below 1550 metres. The rain crusts are variable, but they are giving planar results in tests. At treeline the storm snow is reported to be giving sudden planar results down 40 cm, and the surface hoar/crust layer that is down 80cm is also giving sudden planar results. This tells me that the new load of snow that we are expecting may activate these weak layers. The mid-pack is reported to be strong, and I have not heard anyone talk about early season layers deep in the snowpack.

Problems

Wind Slabs

An icon showing Wind Slabs
Expect new windslabs to develop Saturday night that may become very touchy by Sunday as the temperatures rise and the winds increase.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
Reports of activity on this layer have decreased. Large triggers like explosives and cornice fall have continued to release avalanches that fail down to this weakness. Steep open slopes near treeline may be the most suspect for human triggering.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 7

Cornices

An icon showing Cornices
Warm temperatures and strong winds have caused rapid cornice growth which may not be well supported. Try to reduce your exposure beneath these large unstable masses of heavy snow.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Likely

Expected Size

3 - 5

Valid until: Jan 8th, 2012 8:00AM