South Columbia

Date Issued
    Friday, 12 March 2010 06:00 PM 
Valid Until
    Monday, 15 March 2010 06:00 PM 
Next Update
    Saturday, 13 March 2010 06:00 PM 

S. Selkirks & S. Monashees
				Saturday 		Sunday 			Monday
Alpine 			4 High 			3 Considerable 	3 Considerable
At Treeline 	3 Considerable 	3 Considerable 	3 Considerable
Below Treeline 	3 Considerable 	3 Considerable 	2 Moderate

Purcells

				Saturday 		Sunday 			Monday
Alpine 			3 Considerable 	3 Considerable 	3 Considerable
At Treeline 	3 Considerable 	3 Considerable 	3 Considerable
Below Treeline 	1 Low 			1 Low 			1 Low

Primary Concerns

Persistent Slab

Very warm temperatures and lots of sun over the weekend followed by cooling significantly reduced 
(although not completely eliminated) the potential for triggering avalanches below about 1800m. 
Caution is still warranted on shaded slopes where no crust exists under Sunday night's snow--most 
likely the upper reaches of the BTL elevation band on N - E aspects.

Wind Slab

If the weather forecast is correct, wind slabs will begin to develop on Thursday, especially in 
southern regions at first in the alpine, then perhaps into treeline (check for an update on this 
tomorrow).

Special Message

The Canadian Avalanche Centre has issued a Special Avalanche Warning for certain sections of the 
South Columbia forecast region.

Confidence: Fair

Variability in the distribution and reactivity of the weak layers in a very complex upper snowpack.

Weather Forecast

A ridge of high pressure should build in on Saturday resulting in drier conditions this weekend. 
Expect a mix of sun and cloud on Saturday and Sunday with a freezing level around 1200m during the 
day. Winds should be light to moderate from the south. Monday should see light to moderate snowfall 
with up to 5cm possible. (Updated by Peter Marshall on Mar. 12)

Avalanche Activity

After a significant decline in avalanche activity in the Columbia Mountains over the weekend, there 
was a significant increase (400%) in reported activity Monday and that number doubled again on 
Tuesday. The snowpack just keeps tossing curve balls and I've pretty much stopped trying to predict 
what's going to happen next. Avalanche sizes continue to be quite large. In a very close call 
yesterday, 5 people were caught and 4 fully buried in a 350m wide size 2.5 avalanche which occurred 
on a 5 day old bed surface.

Travel Advisory

Terrain: I think most slopes below about 1800m with a bit of new snow on crusts are mostly good to 
go. Similarly steep, sunny slopes higher up with dust on crust are likely pretty good. All shaded 
areas with no crusts under Sunday night's snow should be treated with great caution.

Risk Management: The biggest problems are concentrated exactly on the aspects and elevations where 
good snow is preserved. Anywhere you are getting good powder riding is highly suspect and should be 
treated with the utmost caution. A high degree of discipline and constant vigilance is required if 
you intend to go into the mountains at the moment. And it's likely to again get trickier in the 
coming days before there's any chance of it getting better.

Snowpack

Strong sun and warm temperatures over the weekend created moist or wet snow on all aspects at low 
elevations and on southerly aspects higher. Cooling then formed crusts and reduced instability in 
these areas. On shaded slopes from high BTL and up, various persistent weak layers remain an issue 
where no crusts formed over the weekend. The crusts and yet another surface hoar layer were buried 
Sunday night and all heck broke loose Monday and Tuesday, mostly on shaded high elevation slopes, in 
spite of relatively light loads. Crikey.

Prepared by KK / GJ