Avalanche Forecast

Issued: Dec 24th, 2013 8:35AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

jlammers, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Wednesday: Mix of sun and cloud / Moderate westerly winds with extreme gusts / Freezing level at 900mThursday: Mainly cloudy with flurries / Moderate westerly winds with extreme gusts / Freezing levels at 1300mFriday: Mix of sun and clouds / Light ridgetop winds / Freezing level at 1100mSpecial Notice: Our radar has just picked-up what appears to be a flying sleigh. Our forecasters believe the sleigh belongs to Santa as it is being pulled by at least 8 reindeer. The sleigh is located in the far north of the province at the 2000m elevation and is currently headed south. More information will be posted as it becomes available.

Avalanche Summary

On Monday there was widespread natural and human-triggered activity within the top 15cm of snow to size 1 in the Elk Valley South area. The activity occurred in response to new snow and wind. No other avalanches were reported.

Snowpack Summary

There appears to be a lot of snowpack variability across the region. Snowpack depths at treeline seem to vary from 50 - 110 cm with high variability in wind-exposed areas. Mostly modest amounts of low density snow have fallen over the last week and may have been shifted into small wind slabs in exposed areas. Located just below the surface is a layer of weak faceted crystals which formed during the cold snap at the beginning of December. At this point, there does not seem to be enough of an overlying slab to create a widespread problem. In the mid pack is the late-November/early-December interface which is made up of surface hoar, a crust, and/or facets. This layer is typically down 30-70cm and is most likely to pose the biggest problem for the region at the moment. Check out this video of a recent snowpack test on this layer. Despite its reactivity in snowpack tests, we have not yet seen widespread avalanche activity on this layer. I suspect it only needs a little more additional load to turn this into a more serious avalanche problem. A buried crust from mid-November can be found near the base of the snowpack below 1650 m and is breaking down into facets.

Problems

Wind Slabs

Light amounts of new snow been shifted into pockets of windslab in exposed terrain. In higher snowfall areas such as the Elk Valley, the new snow has been reported as touchy and reactive.

Be cautious as you transition into wind affected terrain.>The new snow may require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

The most significant persistent interface is a layer of surface hoar buried in early December. It's buried 30-70 cm below the surface and is becoming more reactive in areas where the upper slab has become a little denser.

Dig down to find and test weak layers before committing to a line.>Avoid shallow snowpack areas on steep, convex terrain where triggering is more likely.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Valid until: Dec 25th, 2013 2:00PM