South Columbia

Date Issued
    Saturday, 13 February 2010 02:00 PM 
Valid Until
    Tuesday, 16 February 2010 02:00 PM 
Next Update
    Monday, 15 February 2010 02:00 PM 

S. Selkirks & S. Monashees
				Sunday 			Monday 			Tuesday
Alpine 			3 Considerable 	3 Considerable 	3 Considerable
At Treeline 	3 Considerable 	3 Considerable 	3 Considerable
Below Treeline 	2 Moderate 		2 Moderate 		2 Moderate

Purcells

				Sunday 			Monday 			Tuesday
Alpine 			3 Considerable 	3 Considerable 	3 Considerable
At Treeline 	3 Considerable 	3 Considerable 	3 Considerable
Below Treeline 	2 Moderate 		2 Moderate 		2 Moderate

Primary Concerns

Persistent Slab

Up to three surface hoar layers mixed with weak sugary snow is now buried by a soft slab. These 
layers have become unstable and may be easily triggered. A period of wind starting Saturday evening 
and lasting through Sunday may be enough to initiate a small cycle of natural avalanches in the 
alpine and create very touchy conditions at treeline.

Confidence: Good

Weather Forecast

A series of weak storms will bring light amounts of mountain snow and valley rain to the region 
each day through Monday. A ridge is forecast to build on Monday bringing a drying trend. Tuesday 
another weak weather system is forecast.

Sunday: Snow. Accumulations 5-8 cm. The freezing level rising to near 1500 m. Southerly ridgeline 
winds 30 km/hr in morning.

Monday: A ridge building. Expect a nice day.

Tuesday: A weak front crossing the region may bring the chance of light snow.

Avalanche Activity

Skier triggered avalanches are being reported to size 2.0 on the surface hoar layers. A few 
observers are reporting remote triggering. As snow slowly accumulates and we experience some wind, 
avalanches will become easier to trigger and natural avalanches may occur. Some of these avalanches 
may be size 2.5 or size 3.0.

The December 28th surface hoar layer woke up early in the weak and was remotely triggered by a 
sledder in Quartz creek from a ridgeline. While this is an isolated occurance, it simply illustrates 
that it still has potential in the Purcells and if it goes, it will likely pop out pretty big.

Travel Advisory

On Saturday and Sunday avalnches should be relatively easy to trigger in moderately steep terrain. 
A slab of snow has just reached its tipping point. You won't have to look too hard to find trouble.

Terrain to Watch:  Sparsely treed slopes approaching 35 degrees in steepness, open slopes at 
treeline and the alpine, large convexities, and terrain traps.

Ways to Manage Risk: Setting your sights on Challenging terrain is a good option. This is because 
Challenging terrain gives you choices to ride through terrain that have lower risk with an increasing 
danger.

Snowpack

The February 8 or 10 surface hoar layer is buried 10-20 cm in the Dogtooth Range, but 30-35 cm in 
the Purcell Range southwest of Golden and areas in the Selkirks. This layer is one to watch because 
it was reported 10 to 30 mm in size. It was present on most slopes well up into the alpine. It sits 
on a layer of soft facets, which may limit is future propagation potential, except on some south 
aspects where it survived the sun and rests on a breakable sun crust.

The January 24 and 29 surface hoar layers are buried beneath 20-50 cm. These surface hoar layers are 
failing in stability tests with moderate scores, but more importantly sudden planar or collapse 
results.

The December 28 surface hoar layer is producing sudden planar results in isolated locations in the 
Purcells. It is generally buried 50-70 cm deep.

Prepared by Greg Johnson