Dec 27, 2005 Canadian Avalanche Centre PAF
Avalanche Forecast Issued: December 27, 2005 at 1700 Valid Until: December 27, 2005

South Columbia Region Avalanche Forecast

Forecast Area: This forecast includes the southern Columbia Mountains, including the 
Monashee, Selkirk and Purcell Mountain ranges. This region includes the eastern side 
of the Okanagan Valley from Osoyoos to Enderby, areas south of Highway 1 from Sicamous 
to Golden, areas west of the Columbia River between Golden & Kimberley, and areas 
north of Kaslo and Castlegar. This forecast region does not include Glacier National Park.

Forecast of avalanche danger beginning Tuesday, December 27, 2005:

Day:\Tuesday p.m.\Wednesday\Thursday
Alpine:\Considerable\Considerable\Considerable
Treeline:\Considerable\Considerable\Considerable
Below Treeline:\Moderate\Moderate\Moderate

Travel Advisory: Two avalanche concerns require caution and good avalanche skills to 
travel safely at treeline and alpine elevations. The biggest concern is lingering 
weaknesses deeper in the snowpack that can be human triggered. This is a tricky problem 
because triggering a deep avalanche on one of these weak layers isn't expected to be that 
common. However, pulling out a large avalanche could be devastating. These deep concerns 
will persist for several days with all aspects at treeline and alpine elevations affected. 
The second problem is wind moving new snow into drifts and pillows of slabby snow behind 
ridgecrests & ribs, on steep rolls, and in gulleys. This situation is most likely found 
in pockets on north and east facing slopes. These kinds of avalanches could be common, but 
the avalanches should be small (but enough to bury a person). Good travel habits are 
essential (like exposing only a single person) and sticking to 30 degree slopes is suggested.

Avalanches: Natural avalanches continued at treeline and alpine elevations on most aspects. 
The weak layers were surface hoar or facets under the cap of moist snow, or the deeper late 
November layers. Crowns were typically 30 - 70 cm thick, slope angles were 30 to 40 degrees. 
Several remotely triggered avalanches show that people can trigger slides if they hit a weak 
spot and that slabs can then propagate widely!

Snowpack: Cooler temperatures allowed real snow, not sloppy wet mush, to accumulate. Below 
this 10 - 20 cm of powder is a 20 to 50 cm cap of heavy storm snow - i.e. a slab ~ Wresting 
on the Dec. 19 layer of weak facets & surface hoar. Deeper down (60 - 90 cm) is the late 
November surface hoar-crust combo, and facets. Both these layers are critical weaknesses 
that show easy to moderate strength but fast & clean shears (POPS or DROPS) in stability 
tests. Field observations suggest the deeper November layer may be the greater concern, 
especially in cooler areas like the Purcells west of Golden and Invermere.

Weather: The west / southwest weather pattern continues with moist disturbances embedded in 
the flow. Most of the moisture is passing to the south so Wednesday~Rs accumulations should 
stay within the 10 cm range, a little drier with just flurries Thursday, and maybe some more 
Friday. Yo-yoing freezing levels may hit 1500 m but it looks like more gradual cooling so 
they should start to move to 1000 to 1200 m, and possibly lower.

Issued by: is