Those skiing at Lake Louise early last season may remember that we experienced a widespread avalanche cycle in much of our alpine terrain, losing much of the snow that had fallen to date in places like Brownshirt and Whitehorn II. This was in part attributable to heavier-than-average November snowfalls, which made it difficult for avalanche control teams to get into every piece of terrain before everything slid.
With lower snowfall so far this year, control teams, with the help of other patrollers and the trail crew, have done a great job of getting to where the snow is and using a combination of ski packing and bootpacking to break up the weak layers and temperature crust that exist. All of this work contributes to stability of the slope, and helps ensure the snowpack builds the way we want it to, giving it the best chance to survive the season. With more snow forecasted to fall early this coming week, crews will be constantly working these areas to make sure all new layers of snow are packed in as much as possible. It’s a big job, with huge amounts of terrain to cover, but also with equally huge rewards for all.
Boomerang is a perennial early season performer, as it is a flat, shale-covered surface that receives near-constant wind-loading. It’s usually the first alpine run to be skiable, and therefore often receives the bulk of attention from control teams. On the way to Boomerang is Windy Gap, which can be a vexing place to get snow to stick. I’ve lost count of the number of different ways teams have come up with to get wind-blown snow to stay put. The challenge comes from the wind, which usually blows strongly and can come from any direction (this is why early season skiers may have noticed that the snow fence there sometimes lays in a bunch of zig-zag patterns, rather than in long straight lines like everywhere else on the mountain). In any case, we can’t miss any opportunities to pack down any snow that gathers there, or else run the risk of having it all blow away again. Every flake counts!
In Brownshirt, there’s enough snow for control teams to have begun ski-cutting, which is another slope-stabilization technique. Patrollers travel the run on skis, making big zig-zag tracks down the length of the run. This disrupts the continuity of layers, and breaks up what may be one big slab of snow on the slope into smaller pieces, reducing the likelihood and consequence of an avalanche. You’ll see these ski cuts in all of our avalanche terrain all season long, as it is the preferred method of avalanche control used by patrollers. In sketchier terrain, or when there’s more snow, patrollers will switch to the use of safer (and more expensive) explosives. Generally, frequent smaller dumps are easier to manage than occasional big dumps, which can slow things down as patrollers need to travel more slowly through hazardous terrain. Not that we ever complain about big dumps…
Skiers visiting Lake Louise this week were treated to blue skies and sunshine, thanks to a high pressure system that’s settled in nicely in our area. And while skiers get to enjoy beautiful weather and great visibility on the mountain, this has also meant that our avalanche control team has been able to venture into and spend a lot of time in Whitehorn II.
Good visibility is always welcome during avalanche control work, and sometimes will be the deciding factor on whether the teams go into a certain area. Especially in a place like Whitehorn II, which is a huge piece of steep terrain with ridges, rocks, and cliffs, good visibility provides an extra measure of confidence for the crews traveling there. Stable weather generally results in little change to snow stability, allowing control teams to dedicate more of their time in places they had previously not spent much time in.
Looking back a bit, the week leading up to Christmas saw a few significant weather events, starting with about 20cm of snow that fell with little to no wind. As the snow petered out, the high pressure system moved in, announcing itself with west/northwest winds that redistributed most of that snow. This wasn’t the first time this season that winds came from other than the usual direction, and skiers familiar with how our mountain usually develops would have noticed drifting and scouring in unusual places, and Whitehorn II was no exception.
As a result of strong winds that blew in before the cold snap earlier in the month, the fans (areas at the bottom of slopes where avalanches “fan” out) of Whitehorn II had all their snow blown away, and it was only with the new snow before Christmas that these places had a chance to recover. The more recent winds resulted in hard slab conditions higher on the slopes, and because they came from the west/northwest, snow was distributed across the slope from the side, rather than down from above as is usually the case.
Wind slabs are the result of wind-transported snow. As the delicate snow crystals are blown across the surface, they are broken into tiny pieces. This means they can be packed into a tighter and denser layer of snow, a result increased by the packing action of the wind. Wind slabs often form the most destructive avalanches since they are harder to break apart than softer snow, and must be treated with caution.
One problem that can arise from a thicker and denser slab is that it can be for the most part supportive under the weight of a skier, which can give a false sense of security in the stability of the slope. Features on the slope (rocks, etc) can create weak spots, and even when the rest of a slope seems supportive, one turn in the wrong spot can cause the whole slope to avalanche. In the case of Whitehorn II, this slab was especially stubborn, due to its thickness and density.
When making snowpack observations, avalanche technicians use a scale to describe snow density. Rather than a number scale, as is used to describe sizes of avalanches for example, snow density is described by how easily a certain object will penetrate the layer horizontally (vertical penetration may go through more than one layer of snow, resulting in a variable and inaccurate reading). From least to most dense, the scale goes fist, four finger, one finger, pencil, and knife. The slab in Whitehorn II is pencil, which is about as dense as it gets before you get ice or a melt/freeze layer (knife). In the photo below, you can see that the patrollers’ ski cuts are barely visible at the top of the slope, due to the density of the snow and the inability of skis to penetrate that top layer.
While these slopes have reacted to explosives, the avalanching has not been widespread. In other words, rarely would one bomb be enough to get the whole slope. Snow that should have avalanched but didn’t is called hangfire, and enough hangfire remained in all gullies that many shots were required to clear each slope.
So – where does that leave us in Whitehorn II? It’s not ready to open yet, and while it may be easy to say we’re one or two snowfalls away from opening, there’s more to the picture than just snowfall. Wind and temperature have already played a big part in how the mountain has developed this season, and will also have a role in deciding what it’ll take to get Whitehorn II open. In the end, it’s a big piece of terrain, and lots of work by avalanche control teams will be needed no matter what the weather does.
As promised, here’s a video from the helicopter avalanche control that happened at Lake Louise on November 27. I found a nice perch at the top of Whitehorn II and filmed the action below as the crew dropped bombs in Whitehorn II, Brownshirt, Upper North Cornice, Boundary Bowl (OOB), and along Richardson’s Ridge. Most shots produced little to no result, with the exception of Whitehorn II, Upper North Cornice, and Boundary Bowl. Of the two explosions in the video, the second is the one visible at the top of the gully in a photo from the original post, just from a different point of view.
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.
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!
Weather events since the New Year have conspired to create improved stability in the snowpack at Lake Louise recently, and as things trend from fair to good, there are a few pieces of terrain that should have their gates open for the first time this season if this trend continues.
Closest to being ready is H Gully of Whitehorn II, which has received intense control work in the last little while with lots of bombs and patroller traffic putting the slope to the test. The bombs are always used first to gain confidence before venturing onto the slope, and the patrollers will go (or not) depending on what happens. Once the avalanche forecaster is satisfied with the stability, closure fences need to be set up along both sides of the entire run, as it slices through the middle of closed terrain.
It’s not that common for one the Whitehorn II gullies to stand alone as an open run, other than ‘A’, which usually opens first. The others then open in succession from skier’s right to left as conditions and control work permit. The nutty weather we’ve seen since opening (long cold snaps, huge dump, hot temperatures, and extreme winds) has meant that only ‘A’, ‘B’, and ‘C’ have opened so far. None of the next four have enough snow in them to be skiable.
The final step in opening ‘H’ Gully is not avalanche-related, and involves getting a snow cat up to the top to push in an entrance, as currently you need to take off your skis and walk about 15 metres to get to the top of the gully. The cat track traverse from the top of the Summit Platter has only been in place for a few weeks; otherwise, pushing the entrance to ‘H’ Gully would not be possible. The photo below is an aerial shot of the Windy Gap area, which you pass through on your way to Boomerang. There is less snow currently than in the photo, and the bottom three snow fences have been removed in order to allow the snow cat room to build the ‘H’ Gully entrance.
Building the traverse by cat is tricky, as you need a lot of snow to build a level road across a steep slope. That snow can be found right uphill of the lift shack in the form of the huge drift that forms and runs up to the true peak of Mt. Whitehorn. The cat pushes that drift one bladeful at a time and inches its way across the slope. Snow pushed around by or driven on by a cat will stiffen and become supportive, but it takes awhile. Building a road across a steep slope means lots of snow is needed on the downhill side, and it may or may not support the weight of the cat as it drives over – it depends on the temperature and the condition of the snow. One year, the road collapsed as it was being built, and the cat slid down slope about 30m into the little bowl above ‘D’ and ‘E’ Gullies, and had a bit of a rough time climbing back out.
Another area getting a little closer to opening is Upper E.R. 5, but it’s still at least another 50cm of new snow away from being ready. In particular, the narrow chokes through the cliffs that divide Upper and Lower E.R. 5 have had the hardest time keeping snow and are in the most need. A lot of avalanche control takes place on the upper slopes, and no matter where the results, the avalanching snow always gets funneled through the chokes, stripping them of their snow. This past week, the avalanche control team installed a short piece of orange plastic fence in the middle choke, hoping to catch some of the sliding snow. Looking up now, it does look like there’s a bit of snow there, but it’s so shallow and unsupportive that it wouldn’t survive past the first ten skiers through there.
While we’re hoping for another storm to roll through, there’s still great skiing to be had in the alpine. Dribs and drabs of snow over the past few weeks have softened already smooth runs on the backside, particularly in places like Whitehorn I and Hourglass. Regular Lake Louise skiers already know that it doesn’t take much snow to change the game…
Today marks the one month anniversary of “the storm” – over 50cm of snow in three days. I figured it’d be a good time to finally post some photos from the heli-bombing mission that took place on the morning of January 9. As it turned out, there were three boxes of bombs, and with four people already in the helicopter, I had to give up my seat to one of the boxes. Along with the pilot, there was one patroller lighting the bombs, another throwing them out the door, and a third up front recording the placement and result of each on a shot sheet. The whole thing took about twenty minutes, and results were many, as was clear to anyone skiing the Lake in the few days following.
I always love the way aerial photos show terrain in a whole new light, showing an angle that you just couldn’t get otherwise. The photos below were taken by two of the patrollers on the flight.
In the few weeks since the big storm that left over 60cm of new snow on the mountain, the avalanche control teams have been busy trying to get some more terrain open, proving again that they don’t necessarily need new snow to keep busy. Even in periods of low to no snowfall the teams keep busy by concentrating on yet-to-be-opened terrain. Whitehorn II B & C Gullies opened last week, and ER 6 (Fallen Angel) is getting close, too.
Having a piece of terrain like ER 6 ready to open to the public is the result of weather and the amount of time the avalanche control teams have spent in there. The forecaster must be completely confident that all avalanche hazard has been removed, and that confidence comes from many weeks and months of explosive use, ski cutting, and observation. With some more snow in the forecast, ER 6 opening day is hopefully not far off.
So – how are the conditions in ER 6? The short answer is “variable’, but that probably doesn’t paint that detailed a picture. The main open areas of the slope are nicely compacted, mainly as a result of the avalanches that have run over them in the course of control work, packing down the snow that didn’t get cleaned out. The snow is suprisingly supportive, unless you get too close to any rock features or other traditional weak spots, which are generally soft and uncompacted facets. Facets are a type of snow crystal that forms when there is a strong temperature gradient, or in other words, shallow snow and cold temperatures. Areas around protruding rocks have less snow, and are less able to deal with a large temperature difference between the air and ground (see a previous post for more temperature gradient talk).
Yesterday, we went into ER 6 with two nukes, which is our term for two regular bombs taped together, and two sticks of bamboo. Rather than lob the shots onto the slope like usual, we stuck a bamboo pole in the snow, then taped the nuke to the top end. This is an air blast, which produces a different sort of load on the snowpack than a shot in the snow would. An air blast, while not penetrating as deeply into the snowpack as a thrown shot, covers a wider area, so if you’re only concerned about the top layer(s), an air blast is the way to go.
Air blasts are useful only if you’ve already determined the stability (or not) of the snowpack with ground shots and ski cutting. In other words, you only worry about the top layers after you’ve dealt with the rest of the snowpack. We didn’t get any significant results from either of the air blasts, so our confidence increased even more. Most of the slope is in skiable shape, but there are a few narrow parts where rocks have weakened the snowpack, and likely wouldn’t survive beyond the first few skiers to ski the run. A combination of new snow and some more skier traffic (those doing the control work) should make ER 6 good to go.
The first photo below shows a control team member attaching a nuke to a stick of bamboo. Because the shot is in the air rather than in the snow, the sound of the blast is much louder, so we’ll generally retreat a little farther away to await the explosion. As shown in the second photo, the poor bamboo doesn’t fare all that well!
As our team was controlling ER 6, another was making their way down the ER 5/6 ridgeline to control Upper ER 5 and the Kiddies Corner area. This is a longer route that requires the team to make their way on foot over rough, rocky terrain and down a steep ridge. We wanted to get these areas controlled as soon as possible so that the surrounding back side terrain could open without too long a delay. For these routes, patrollers will ride Top of the World chair, then take their skis off and walk up to the top of Paradise chair and the start of the control routes. This is much faster than skiing to and riding Paradise chair.
The photo below shows a control team nearing the bottom of the steep part of the ER 5/6 ridge, just above a slope on ER 5 called the Big Kahuna (not visible in photo, but visible from Paradise chair).
Another beautiful sunny day at Lake Louise today, and the avalanche control team made use of the good visibility to try and get some results in E, F, & G Gullies of Whitehorn II. Previous attempts to get results with our regular 1kg and 2kg shots were unsuccessful, so we decided to pull out the big guns – ANFO, that is.
ANFO stands for ammonium nitrate and fuel oil, and comes in large bags. It looks like lawn fertilizer, and can be used to make custom size shots to fit the needs of the control team. In this case, three 7kg bombs were made by placing the ANFO in separate bags, then inserting a 1kg shot with fuse and igniter.
We loaded the lift around 8:30 and arrived at mid-station just as the sun was beginning to peek over the mountaintops. By the time we got to the top of Summit, Whitehorn II and the rest of the backside was bathed in a beautiful early-morning light. I travelled around to Shoulder Roll on Boomerang so I could get some photos of the action (if there was going to be any). The first two shots were used in E and F Gullies, and both produced very minor results – just a little surface snow around the shot placement.
The shot in G Gully was a different story. As shown in the photos below, as soon as the bomb went off, fracture lines appeared along almost the entire vertical length of the run, and the slope avalanched down to the bottom and up the other side of the terrain slump that runs along most of the bottom of Whitehorn II. This was a size three avalanche, enough to bury or destroy a car. One patroller was asked why Whitehorn II hadn’t been open yet, and the reply was, “Go ski Boomerang, then look up to your right and you’ll get your answer”.
In the wake of the storm that left over 60cm of new snow on the mountain, the avalanche forecaster was forced to consider parts of the mountain that normally aren’t a problem with regards to avalanche hazard. While many of the places are in the alpine, there are also a few that are tucked away in hard-to-find pockets hidden in the woods. While hard to find, they’re still in open terrain, so must be considered when planning the day’s avalanche control. Four of these areas are located on the front side of the mountain - Midstation Pocket to the skier’s right of Men’s Downhill, Ladies’ Pocket to the skier’s right of Ladies’ Downhill, Comer’s below Eagle Meadows cat track, and Paradise Pocket just above Pine Cone Way. These pitches aren’t big enough to attract those looking for untouched powder, but they are big and steep enough to avalanche and do get traffic nonetheless.
On Saturday, two of us headed towards Comer’s and Paradise Pocket, since both can be controlled on the same lap. Dropping into Comer’s, there was lots of snow, and it was also apparent that there had been traffic throughout the storm, stabilizing the snow. Ski cuts here did not produce any results. Moving down to Paradise Pocket* the signs of traffic became less and less, and when we arrived at the top of the slope, we were pretty sure we’d get results.
Since the pocket looms directly over Pine Cone Way, we called a patroller to do a spot closure at the top of the run. A spot closure is just a temporary and usually brief closure of a run with a patroller standing guard rather than setting up closure fences and signage. Once the run was secured, we began by putting a ski cut across the top of the slope, which produced an immediate result as most of the feature avalanched the full length of the pitch. The skier’s left 1/3 of the slope did not slide, so I ski cut the top and got all of that to go as well. The debris ran to within a metre or two of Pine Cone Way, so not only were we glad to have closed the run, but also to have controlled the slope and removed any avalanche hazard.
The next photos are of Paradise Pocket before and after the avalanche, and you can see in the first how close the pitch is to Pine Cone Way. And, a short video (0:10) shows the first ski cut getting a good result.
It’s always good to go to places that are seldom visited in the course of a work day – there’s always something to be learned.
*It may seem strange that a pocket on the front side is named after a chair on the back side, but Paradise Pocket was named long before the chair of the same name existed. Perhaps it was named after Paradise Valley by Mt. Temple?