Avalanche Forecast

Issued: Dec 23rd, 2013 8:15AM

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

jlammers, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Wind effect is extremely variable

Weather Forecast

Tuesday: Mix of sun and clouds / Light southwest winds (with extreme gusts) / Freezing level at surfaceWednesday: Mainly cloudy / Moderate west winds (with extreme gusts) / Freezing level at 1000mThursday: Mainly cloudy / Light winds / Freezing level at 1100m

Avalanche Summary

In the southeast corner of the region explosives control produced a size 2 wind slab avalanche on a southeast facing slope on Sunday. No other avalanches have been 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. Dribs and drabs of low density snow have fallen in the last few days 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

Persistent Slabs

The most significant 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.

Avoid shallow snowpack areas on steep, convex terrain where triggering is more likely.>Dig down to find and test weak layers before committing to a line.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Wind Slabs

Light amounts of new snow may have been shifted into pockets of small windslab at upper elevations. Watch for triggering in the lee of ridgecrests and terrain breaks.

Be careful with wind loaded pockets. Be aware of wide variation in snowpack depth>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 24th, 2013 2:00PM