More Powder at the LakePosted: November 18, 2009
The last few days at Lake Louise have seen some turbulent weather, as the latest system to roll through came in like a lion (high winds), and went out like a lamb (fluffy snow). Yesterday (Tuesday), most lifts on the mountain closed for at least part of the day as high winds played havoc with both our lifts and avalanche closure fences and signs.
Since the wind we get at Lake Louise usually comes from the south/south-west, the front side lifts are more susceptible to wind closures, and once we started getting gusts in excess of 80km/h at the top of the Grizzly Gondola, the time came to stop loading the lift and wait for the wind to subside a bit. Top of the World chair followed shortly after. Chairs can swing wildly in high wind, and the chance of a line derailment increases if the lift is moving. Also, if the lift were to stop, we have to think about any people who might be sitting on the chair and exposed to potentially unsafe conditions.
The other alpine lifts – Paradise and Summit – remained open, at least for the short term. Paradise is on the leeward side of the mountain, and riders don’t get a sense of the wind that’s pounding the front side until they get to the last few metres of the ride. The one thing we need to make sure of there is that people are able to unload the chair without the wind blowing them back into their seats. The Summit Platter is a surface lift, and therefore is not subject to the same issues as a chair lift in high wind.
At the same time, both Paradise and Summit did close, but not for lift-related reasons. While traveling down the fence that separates Paradise Bowl from Upper ER 5, and avalanche control team noticed that entire sections of closure fence and their signs were being blown away. Without the ability to maintain these vital fences during the wind, the avalanche forecaster decided it was best to close all alpine terrain until the wind let up and we could get a chance to ensure all avalanche closures were in place.
This morning we arrived to a different scene. The winds had almost completely abated, and another 10cm of new snow had fallen during the night. The avalanche forecaster had a tricky morning of doing his stability checklist and deciding on the best course of action for the day’s control work. Not only were the winds from the previous day blowing strong, they were also coming from other than the usual direction, which means re-thinking every bit of avalanche terrain and having the teams ready for anything.
My team headed straight for Summit, and after hiking up to the peak, skied down over the Boomerang entrance traverse and made our way to the top of D Gully in Whitehorn II. We had 5 explosive shots with us – three single shots, and two nukes (two shots taped together). Due to a combination of high wind, moving snow, and the predominant rain crust and facet combination that has been causing natural and manmade avalanches all over the national park, we expected big things, especially in terrain like Whitehorn II, where there has not been extensive control work.
Once at the top of D Gully, I attached an igniter to the fuse of one of the nukes, lit it, and threw it down as far as I could so that it landed on the skier’s left flank of the gully, well above the narrow choke about halfway down and the part of the slope that generally produces results. The bomb went off, and while nothing but surface snow was affected around the shot placement, it did cause an avalanche to start about 30-50m downslope. All snow above the October crust ran, and it included the full width of the gully by the time it got to the choke, running far out onto the flats at the bottom.
Satisfied with that result, we began to make our way over the top of C Gully to do the same thing there. My partner began the traverse, and was no more than a few metres into it when suddenly there was a “woomph” as his weight caused the weak layer in the snowpack underneath him to collapse. he heard and felt this happen, and immediately looked around to see if the slope was avalanching. The snow around him stayed in place, but as we looked downslope, we saw that another large avalanche had started about 60 or 70 metres below, and, like in D Gully, was running on the crust and went pretty much side to side. This was a remotely triggered avalanche, since the start point was different from where the load (weight of skier) had been placed on the snowpack. In all likelihood, the weak layer of facets had collapsed under his weight and travelled horizontally to a point in the snowpack where there was enough tension, and possibly a weak point (boulder or other ground feature), resulting in the avalanche. This was similar to what we saw in Whitehorn I recently, when a patroller traveling well underneath the slope remotely triggered an avalanche far above him.
With the avalanche starting far down slope, we were concerned about the snow higher up that did not slide (hang fire), and there was still quite a bit left. A single shot was thrown ahead of our progress, and when the explosion did not result in an avalanche, our worries eased.
Watching a slope get most or all of its snow taken away by an avalanche can be heartbreaking, but when you have such a suspect layer in the snowpack that’s producing avalanches all over the place, it has to be done in order to let the run rebuild itself. Otherwise, we’d spend the entire winter worrying about it. Now, at least in the places that have avalanched, that layer is no longer a concern, and the slopes have a chance to rebuild with a sturdier snowpack.
With most of the morning’s control work done, control teams can concentrate on ski cutting and getting ready for the next system to come our way. The forecasts are calling for more snow tonight and tomorrow, so the sooner we can rid ourselves of the weak layers, the sooner the slopes can begin the rebuilding.