Conditions Report - Exception to the Public Avalanche Bulletin - Cloud Nine Guides AST 2 Course

 

Hey all,

 

Some thoughts on the current Rockies snowpack for you over your morning coffees; and some exceptions we've made to it based on our field observations during the past 48hrs on one of our Rockies Based AST 2 Courses. Portions of the core curriculum on course provide students with a process to make these exceptions to the Public Avalanche Bulletin, and when and how it can be done without unreasonably elevating risk to the group or individuals on course - we chose to make one of these exceptions and the group felt it would be worth sharing our obs.

 

The exception we chose to make was related specifically to the removal of the Wind Slab Problem in the Public Avalanche Bulletin on December 28th. Given the recent drought and extremely cold weather, it made sense to the group that the faceting process that's been driving the past few weeks had likely removed much of the slab properties present in the snowpack but required further verification.

 

Our Ski Programs over the past few weeks, as well as the first field day of our AST 2 Course this week on December 28th, have found generally  stable conditions with lot's of opportunity to push most of the terrain we've accessed. Yesteday, our group decided on a tour up and over the Twin Cairns in the Sunshine Backcountry. Most courses we have run in past years in this area have had plenty of snowpack issues for AST 2 Teams to observe and learn to manage, one of the main reasons we go. As described above, our conversation in our Group Meeting / AM Guides Meetings yesterday morning prior to departing for our day, was based mostly around the forecasters removal of the Wind Slab Problem from the Public Avalanche Bulletin (Banff, Yoho, Kootenay) and whether we felt that would be representative of the areas we wanted to access. On the drive home the evening prior we observed significant wind and snow at valley bottom elevations near Banff which at very least allowed room for some curiousity about the alpine conditions the morning of the 28th. Our thinking was there may still be potential for slab-like properties to exist on isolated features in the forecast area and that it would be prudent to gather as much info as we could prior to accessing or exposing ourselves to any slopes of consequence on the Cairns.

 

On average much of the snowpack we traveled through in the Sunshine Meadows, though heavily faceted, was still presented slab properties of varying hardness. Tests on small indicator slopes on approach also produced clean shears on an interface below a windslab failing 40-50cm down. No other signs of instability were observed (cracking, whoompfing, hollow sounds) and results and info we were getting were in predictable places and very isolated (ie: not widespread).
 

We accessed the summit ridge via the south end, and a bootpack up and over the summit, we had a look at possible descent lines down the East Face. After a discussion on the summit the group felt that the information we'd gathered to that point wouldn't be sufficient to ski without incorporating information from a snow profile and snow stability tests on the feature. In the process of accessing the proposed descent line and profile site, while moving the group along the very upper margins of the start zones, experienced a large settlement and shooting crack that traveled (from what we could see at least) 25+ meters across the slope fore and aft of the Guide setting the track. 

 

It's never comforable to see these signs of instability and the perception of exposure on the ridge line of the Cairns can feel a bit out there especially for those with developing skill sets, but the group felt well placed having discussed the hazard and associated risk levels prior to entry, and managed their position in their start zone and were well spaced  and placed prior to crossing the slope.

 

So why the exception to the Public Avalanche Bulletin & Problems?:

 

As our group read the Public Avalanche Bulletin on the morning prior to our departure, our group discussions and the discussion in our morning Guides Meeting were centered around the suggestion that there were currently no problems in the snow pack that could produce a slab avalanche, or at least that's the message we took from it as a group. The only problem present was listed as a Loose Dry (basically a facet-alanche) type problem, which despite the forecast size at 2.0, generally speaking, doesn't present the same level of consequence or risk to skiers/riders as a slab avalanche would. We felt after signifigant discussion that the by removing the WSL problem from the bulletin made an underlying suggestion that there would be an almost a non-existant chance we would see signs of instability in the snowpack that would speak directly to the presence of slab like properties - like the whoopf and shooting crack we observed later in the day.

 

It should be clarified that the signs of instability (whoompf and shooting crack) we observed did not come from a windslab at the ridgecrest, but instead from our group triggering a basal facet structure in a very thin snowpack location at the ridgecrest - a very predictable response from the snowpack, given what we were up to. Where we felt the exception was needed, was that the message we felt was being delievered from the Public Avalanche Bulletin led us to believe an avalanche with slab properties weren't (likely) going to exist in the forecast area.

 

Worth Remembering: 

 

In the AST 1 & 2 Courses, the curriculum covers specific limiations of both local and regional avalanche forecasts. We don't provide our experiences here to refute the forcase provided by the forecasters, in fact we it's provided to serve as a reminder that spacial variability does in fact exist, and we managed to find an area yesterday where an exception existed with fairly serious consequence. Had we triggered the slab, and/or been poorly positioned in the terrain the result could have been catastrophic. Further to that, yesterday served as a good reminder to our group that green doesn't always meen go when you see it in the bulletin. It is our responsiblity to either confirm or deny whether specific problems in the Public Avalanche Bulletin exist in the areas we plan to spend our time. Our exception made, led us to pull the reins in in a real way yesterday.

 

Further, we felt making an exception to the problems listed yesterday was reasonable given that it led to a more conservative approach to our decision making after the event, as opposed to making an exception that would see us stepping out further and increasing our risk. It's a much lower risk action to be making exceptions like this during periods of LOW of MODERATE Rated Hazard which we've had recently, as opposed to making exceptions to the Public Avalanche Bulletin when the Hazard is Rated as CONSIDERABLE or Higher.

 

So... Despite the great stability as of late and all the fun we've been having tagging summits, and skiing bigger steeper terrain, we're definitley going to be recallibrating our thinking and approach as we roll through our next couple AST Level 2 Courses over the next couple weeks.

 

Some food for thought :)

 

Hope you enjoyed that morning coffee, and if you have any questions or would like more info on our observations yesterday feel free to email our Guiding Team at info@cloudnineguides.com. If you found the info useful please give it a share via your Facebook Profiles and spread the info for others in the community.

 

The Cloud Nine Guides.