Avalanche Forecast

Issued: Feb 15th, 2013 9:44AM

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 Persistent Slabs.

triley, Avalanche Canada

Cariboos.

Forecast new snow is expected to add a new load above the recent storm snow that may cause the buried February 12th weak layer to continue to be reactive.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Overnight and Saturday: Strong Westerly winds are expected as the ridge of high pressure flattens and a trough moves into the interior from the Northwest. Alpine temperatures should stay a few degrees warmer than seasonal overnight as the weak warm front delivers a couple of cms. Moderate snow fall should start sometime in the morning when the trailing cold front moves across the region. Expect 10-15 cms with cooler temperatures and gusty West winds.Sunday: Unsettled cool air will be left behind as the next ridge of high pressure builds over the interior. Expect light Northerly winds and alpine temperatures down to about -12.0, with no precipitation.Monday: Mainly cloudy as the weak ridge of high pressure moves to the East.

Avalanche Summary

Reports of storm snow avalanches are getting fewer, as the slab settles. Some natural cornice falls have been reported. Reports from some of the managed snowmobile areas are saying that the areas that have received a lot of compaction are not seeing storm snow avalanches. However, there is a concern that people who have been riding in these areas may be surprised by an active storm slab if they venture into lesser ridden areas, or steeper terrain that has not seen as much compaction.

Snowpack Summary

There is a lot of variability in the new snow amounts across the region. New storm slabs are between 10-40 cms deep, and new wind slabs are up to 70 cms deep due to strong Northwest winds transporting the available new snow. Tests are showing easy to moderate shears at the storm snow interface. There are a couple of deeper buried surface hoar and crust layers that have been giving hard resistant planar results in snow profile tests. These deeper layers are not expected to be triggered by light additional loads, but may be triggered by storm snow avalanches in motion, or cornice fall.

Problems

Storm Slabs

The recent storm slab is reported to be settling into a 20-25 cms slab that is variable (soft-stiff) depending on aspect and elevation. The forecast snow and wind are expected to add a new load above this reactive weak layer.

The new snow will require several days to settle and stabilize.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Wind Slabs

Wind slabs are a couple of days old and reported to be less reactive. Expect new windslabs to develop with the forecast snow.

Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

There are older layers of buried surface hoar and crusts that are buried down about 80-110 cms. These layers continue to show results in snow profile tests and may be triggered by large additional loads.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Feb 16th, 2013 2:00PM