Not a Cloud in the SkyPosted: February 27, 2009
It’s been a fantastic week at Lake Louise, with a big storm dumping lots of fresh powder all over the mountain on Tuesday and Wednesday, followed by two days of bluebird on Thursday and today (nothing like a couple of sunny days on the slopes to recharge the ol’ batteries, eh?). The cats did a great job of laying down a whole lot of corduroy last night, and carvers had these groomed runs all to themselves for most of the morning.
When the avalanche forecaster arrived at work this morning, the weather data from our Paradise top telemetry station reported about 12 hours of 30km winds or greater, starting right when the hill closed yesterday. Upon seeing this, his initial reaction was to expect significant wind-loading on lee slopes, since there was lots of fetch (snow available to be transported by wind) after the storm, and 30km winds, especially 12 hours of them, can move a lot of snow.
Since it was a clear morning, the forecaster grabbed his binoculars to see if he could see any signs of wind effect on the front side of Summit, which can be seen right from his desk. Contrary to what he expected, there were no signs at all of any scouring, which is the usual result when the wind comes from the southwest. That could mean a couple of things – either the cold temperatures immediately following the storm stiffened up the snow enough so that the wind couldn’t move it, or the winds were just low enough to hit our weather station, but none of the terrain. Once we got on the mountain, it was clear that it was the latter, since the new snow was still soft and would definitely have moved had the wind been low enough to do so.
On avalanche control, my partner and I headed to B and C Gullies of Whitehorn II, and when we unloaded the Summit lift we could see without even entering the run that the wind had only blown minimal amounts of snow, which had settled between the bumps that lie in the first 15 or 20 metres of the slope. Below that, there was no sign of wind-transported snow at all. The photo below shows the gate into Boomerang, and you can see the snow that was blown onto the cat track overnight, which isn’t much.
Once we were done in Whitehorn II, we went to join another team over at North Cornice, which had developed a bit of its namesake cornice from the wind that circles around from Bare Ass Pass and hits it from behind. As in other places, the loading was limited to the immediate lee part of the slope, so for the most part our mission was to knock the cornice down before it had a chance to grow too big and become a safety issue.
When controlling a cornice, the first team member will travel along the top of the ridge, kicking the cornice with their ski and trying to get it so that there is no overhang. The second patroller will travel behind the first and a metre or two below, ski cutting the slope that received the loading. Although it wasn’t in this case, kicking cornice can be a little frightening, since you hope that you’re not standing on the piece that decides to fall! If there’s any indication this might be the case, a patroller will travel along with the one doing the kicking, hanging on to them so they can pull them back if needed. The photos below show three patrollers as they move along North Cornice towards Lake Pitch, which is the eastern end of the feature and so named due to the little lake that lies in the flats below but hidden from view by ice and snow in the winter (click the link for Summer 07 to the right to see a photo of this area in the summer).
When we arrived at Lake Pitch, we could see pillow of wind-loaded snow that might be a concern, and while nothing we had seen so far this morning indicated it would be an issue, it was decided that to be sure we should use an explosive. When the snow is firm, like it was here, you need to tie the shot onto a length of cord and hang it over the cornice – otherwise you risk the shot bouncing on the surface and ending up at the bottom of the slope, where it is of little use. In the first photo below, you can barely see the shot hanging in place (though you may need to click on the photo for a lrger version to see better).
As you can see in the last photo above, only the top 5cm or so of snow reacted to the bomb, and we were satisfied that Boomerang, Brownshirt, and North Cornice were good to open. As we made our way back to Paradise chair, we watched two other control teams put some more ski cuts into Upper ER 5, which is slowly but surely getting closer to being open. Not yet, but we`re hoping soon!