Avalanche Forecast

Issued: Mar 17th, 2013 10:48AM

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

jlammers, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Monday: Light snowfall / Moderate to strong northwest winds / Freezing level at 1100mTuesday: Generally clear skies / Light southwest winds / Freezing level at 1300mWednesday: Moderate snowfall / Moderate southwest winds / Freezing level at 1500m

Avalanche Summary

No new natural activity was observed on Saturday; however, observations were somewhat limited. Having said that, numerous size 1.5 avalanches were triggered on various aspects between 2100m and 2300m by machines or by humans, one of which was remotely triggered from 10m away. In all cases the March 10 interface was the culprit. I would expect a new round of wind slab activity in response to new snow and wind on Saturday night.

Snowpack Summary

Generally moderate amounts of new snow fell on Saturday night and have have been distributed into deeper windslabs in lee terrain. These new accumulations overlie a deep and cohesive storm slab which formed last week with strong winds, very heavy snowfall and warm temperatures. This deep storm slab produced widespread and destructive avalanches in the region and may take some time to fully stabilize as it overlies weak surface hoar buried on March 10th. At lower elevations heavy rain penetrated the snowpack; however, subsequent cooling has helped strengthen the snow.Deeper weaknesses in the snowpack have now become unlikely to trigger.Widespread cornice development has also taken place, and cornices are reported to be very large and weak.

Problems

Storm Slabs

New snow accumulations have added load to an existing storm slab problem which produced destructive natural avalanches prior to the weekend. Current reactivity is most likely in areas where buried surface hoar exists.

Be wary of slopes that did not previously avalanche - even on low angle terrain.>Conditions have iimproved, but be mindful that deep instabilities are still present.>If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 6

Wind Slabs

New snow on Saturday night and continued winds have created new wind slabs. Watch for loading on a variety of aspects due to variable wind directions.

Avoid travelling in areas that have been reverse loaded by winds.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Recent stormy weather has formed large and potentially weak cornices. Cornice falls may be highly destructive, and could also trigger large avalanches on the slope below.

Do not travel on slopes that are exposed to cornices overhead.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 6

Valid until: Mar 18th, 2013 2:00PM