Kootenay Boundary

Date Issued
    Monday, 04 January 2010 05:00 PM 
Valid Until
    Thursday, 07 January 2010 05:00 PM 
Next Update
    Wednesday, 06 January 2010 05:00 PM 

 
	            Tuesday 	    Wednesday 	    Thursday
Alpine 	        3 Considerable 	2 Moderate 	    2 Moderate
At Treeline 	3 Considerable 	3 Considerable 	3 Considerable
Below Treeline 	3 Considerable 	3 Considerable 	3 Considerable

Primary Concerns

Persistent Slab

Surface hoar buried 40-60 cm deep is reactive to snowmobilers and skiers. This instability is 
most prevalent on alpine like terrain features at treeline, treeline, and below treeline. 

Confidence: Fair

Weather Forecast

Tuesday: A ridge of high presure should bring clearing skies. Excellent days in the mountains 
ahead. Along with Sun, expect the a freezing level to pop up to near 1000 m. North aspect will 
be cool, south apsects warm.

Wednesday: Cool and clear prevails. The freezing level may reach 1200m.

Thursday: Continued cool and clear. There might be some clouds rolling in the afternoon.

Avalanche Activity

Snowfall on Monday will probably build an ideal slab for triggering avalanches with sleds and 
skis for Tuesday and Wednesday. Conditions are very similar to areas a little further north in 
the South Columbia where remotely triggered avalanches from skis, sleds, and helicopters were 
reported.

Travel Advisory

Bluebird, deep pow, and buried surface don't exactly mix well if you are trying to get after 
it. There are a few times during the winter to really watch it. Now is one of them. A persistent 
weak layer of surface hoar in the snowpack is unstable and has the capability of releasing large 
avalanches. This instability will probably linger in the snowpack for sometime.

Terrain to Watch:

It is critical to avoid open slopes steeper than about 30 degrees at treeline and below treeline. 
There is a very good chance of triggering an avalanche in this type of terrain. Be especially 
careful in cutblocks, where surface hoar is often prevelant and very unstable.

Techniques for managing hazard:

Plan trips with an extra margin of safety. Give yourself an ace card and choose terrain with lots 
of options to avoid steep open slopes and terrain traps. Be cautious while traveling under steep 
and open terrain. Triggering an avalanche from below is a distinct possibility.

Snowpack

A soft slab 40 - 60 cm thick overlies the Dec 29 surface hoar and suncrust layer. The surface hoar 
is patchy in distribution at treeline and widespread below treeline. It is most prevalent in north 
and east facing glades. On southerly facing slopes a sun crust exists at this interface. In places 
surface hoar probably rests on the crust. Given the nature of this layer, expect easy to moderate 
stability test results with a clean shear. Additionally, expect propagation tests to indicate this 
layer will propagate if a fracture is initiated. If you don't see these results, I wouldn't assume 
it is safe.

Below the surface hoar are old rounding facets that are probably gaining strength. The lower 
snowpack is strong.

Prepared by Greg Johnson