South Columbia

Date Issued
    Sunday, 17 January 2010 04:00 PM 
Valid Until
    Wednesday, 20 January 2010 04:00 PM 
Next Update
    Monday, 18 January 2010 04:00 PM 

S. Selkirks & S. Monashees

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

Purcells

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

Primary Concerns

Persistent Slab

Many slopes avalanched during this week's natural cycle; exercise caution around those (gentler) 
slopes that didn't. Originally thought to be a treeline problem, the latest evidence suggests this 
may also be a lower alpine issue.

Wind Slab

Moderate to strong southerly winds have lee loaded alpine and open treeline features.

Special Message

A Special Public Avalanche Warning was issued for this weekend.

Confidence: Good

Good for the tricky snowpack structure and difficult conditions.

Weather Forecast

A large low pressure system in the northwest pacific will push weak disturbances into the interior 
region over the forecast period.

Monday:  Cloudy with light to locally moderate precipitation.  Freezing levels will hover around 
1300-1500m and winds will be light but gusty from the southwest.  

Tuesday/Wednesday:  Continued clouds with light snow in the southern portion of the region.  
Freezing levels remain between 1300m and 1500m with light, gusty, southerly winds.

Updated January 17, 2010 by Matt Peter

Avalanche Activity

A widespread avalanche cycle continues to be reported. The number of avalanches is on the decline. 
Surprisingly the size of them is also on the decline - mostly size 1.5 to 2.5. Here's how I 
interpret it: people haven't been in the alpine or have lousy visibility; many of the big slopes 
have run; and people are avoiding avalanche terrain and giving it a wide berth. I think avy size 
will grow again with today's wind and snow load. I suspect we're going to hear more about avalanches 
releasing above say 1800m (Treeline elevations). Until now the lower elevations is where the 
action's been; looking forward I think low alpine elevations will be a place to watch.

With improved visibility on Saturday, many large avalanches have been reported.  These have been 
releasing on the December 29th surface hoar layer (as deep as 100cm) and running fast and far to 
size 3.0 from low alpine and treeline elevations.  

Updated January 17 - Matt Peter

Travel Advisory

Professional avalanche workers (like guides) are by and large working hard to avoid avalanche 
terrain of any size or consequence. The western Monashees - areas west of Revelstoke and Nakusp - 
seem to have better conditions.

Terrain to avoid: Avoid open slopes that have not yet avalanched especially near treeline or low in 
the alpine. I'd skip big terrain like bowls and steep convex rolls. Avoid exposure to terrain traps 
such as gullies, cliffs, and thinly spaced trees. Cornices could have grown unstable and they're 
impossible to forecast.

Ideas to manage risk:  Think boondocking not hill-climbing. Staying safe over the next few days will 
require careful terrain selection. Stick to previously avalanched slopes. If it didn't avalanche, 
I'd dig to check out the surface hoar to ensure it's not there. Watch or avoid exposure to terrain 
traps & overhead hazards - you don't want a cornice or some big alpine slope coming down on you. 
Watch for clues such as shooting cracks, whumpfing, or recent avalanches. Finally, work with your 
group: only one person on a slope - don't go help dig out your buddies sled when it gets stuck; 
regroup in safe spots; watch the rider on the slope. Or, if you are the rider, know where your exit 
is.

Snowpack

Friday's wind and new snow building surface windslabs which likely extend down to treeline and on 
crossloaded terrain. The new snow is upside down which I'm guessing is sensitive on slopes that 
aren't wind affected, at least for now.

Purcell's are reporting up to 50 cm storm snow over the past few days. Monashees and Selkirks it's 
more like 75 to 100cm. Localized heavy snow Friday could easily add 30cm to these numbers. Below 
all this snow is the New Year's surface hoar; sandwiched somewhere in the middle is the Jan 6 
surface hoar.

The early January and late Dec surface hoar layers remain the primary concern, especially near 
treeline. This December layer is widespread at and below treeline, but lurks in sheltered areas of 
the alpine. Many slopes have avalanched but heads-up for those that haven't.

Prepared by ilya storm