9cm in 24hrs

Blue skies have once again turned grey this week as another weather system has moved in and blanketed the Lake in snow – 9cm in the last twenty-four hours, and 20cm in the last three days. It’s still snowing, and except for a few short breaks, the snow is expected to continue until the end of the weekend. With already great conditions and virtually all runs open, a great spring just got better, so those golf clubs may have to stay hidden away for a few more weeks yet!


Lipalian 3 Avalanche: Update

There have been a few requests for information about the slope involved in the March 26 avalanche in Lipalian 3. That information, as well as the avalanche history, have been added to the bottom of the main post below.


Avalanche in Lipalian 3

Shortly after lunch on Saturday, two skiers riding Larch chair looked up above and to the right of the top of the chair towards the Lipalian chutes and happened to see a skier starting to ski a slope not far outside the ski area boundary. The skier had only made a few turns when most of the slope began to avalanche, which ended up carrying the skier down slope and out of view of those riding the chairlift.

The witnesses reported the avalanche to the lift attendant at the top of the chair, who passed along the information to Ski Patrol dispatch. Dispatch then informed an avalanche control team member, who was in Temple Lodge and immediately began making his way to Larch chair. He also called the patroller stationed at the top of Larch to ski over to the ski area boundary, which runs down the small ridge dividing Lipalian 1 and 2, and report what he saw.

At the same time, another control team member was riding Larch chair and saw that Lipalian 3 had slid. He turned his radio to the patrol channel to report the slide and came into the middle of the communication that was already taking place. Upon getting a closer view, he was able to confirm that most of Lipalian 3 had slid, and that there were two sets of tracks entering the slide from the top. He looked to see if tracks exiting the avalanched area were visible, but the debris field at the bottom was quite big, making it impossible to see if that was the case.

Because of the uncertainty about whether there was anyone caught and buried in the slide, Dispatch also called the Banff National Park public safety specialists and requested rescue assistance. There happened to be a helicopter already in Lake Louise about to make a trip to the Skoki area, and while it was not equipped with rescue personnel or gear, it still flew over the area to assist by viewing the avalanche from above and looking for clues on the debris surface.

A short time later, ski area staff were approached by two males outside of Temple Patrol, near the base of Larch chair. The two identified themselves as the ones who had triggered and were in the avalanche, and were able to confirm that there were no others on the slope at the time. Upon receiving this confirmation, the search was called off, and the two involved parties accompanied a patroller to the top of Larch chair so that they could join the patrol staff that were already there and discuss the incident, with the aim of gathering  as much information as possible.

After interviewing the two involved parties, a clear picture of the event emerged.

After riding Larch chair, the two started the hike that leads to Elevator Shaft and Purple Bowl, then cut off around the top of upper Lipalian 2. After riding that pitch, they traversed slightly skier’s left and arrived at the rollover that marks the top of Lipalian 3. Seeing a long untracked pitch below, they decided to go down that run. The snowboarder went first, making wide fast turns down the length of the slope and stopping at the bottom and off to the side. The skier went next, and had only made a few turns when the slope started to avalanche. The skier ended up sitting down on the sliding snow, yelling to his brother at the bottom of the slope. Near the bottom, the slide carried the skier into a tree, then came to rest shortly after. Because the avalanche had slowed considerably by then, the skier escaped with only a glancing blow with the tree. Except for one short period of time, the skier remained on top of the slide the whole way, and was still on top when the slide came to a stop. He immediately looked around and yelled for his brother, who had watched the whole event safely from out of harm’s way. They quickly gathered themselves and made their way off the debris field and down toward the base of Larch chair.

Returning to the scene after the event, snow safety staff determined that the slide was a size 2.5, had a crown depth that ranged from 40cm to 100cm, with an average of 60cm, and ran for about 200m. A size 2 avalanche typically has a mass of 100 tonnes and can bury, injure, or kill a person. A size 3 has a typical mass of 1,000 tonnes, and could bury or destroy a car, damage a truck, destroy a wood frame house, or break a few trees. This slide was right in the middle of the two.

Lipalian 3 avalanche. (photo: Dave Petch)

 

Lipalian 3 avalanche. (photo: Dave Petch)

Lipalian 3 avalanche. (photo: Dave Petch)

 

With all the information we received, nothing painted a clearer picture than the video footage captured by the skier’s helmet cam, which dramatically shows how quickly things happen. From the top of the slope, you can see the tree the skier hit in the slide, and while it’s difficult to get a sense of the slide’s speed while it’s happening, note that it took just over twenty seconds from the start of the slide for the skier to reach the tree at the bottom of the slope.


I filmed this next short clip during the heli-bombing that took place in that area on December 15, 2010. As mentioned in the avalanche history of that slope at the bottom of this post, a shot thrown from the helicopter onto Lipalian 1 triggered sympathetic releases in Lipalian 2 and 3, and all three slopes can be seen avalanching as the helicopter returned to fly over the area once the shots had gone off. Keep in mind this was a very different place in December, as we had yet to experience the near-record January that added so much snow to the slopes. The bowl of upper Lipalian 2 can be seen above the line of exposed rock visible at the top of Lipalian 3. As the helicopter flies over Lipalian 1, then 2, and finally 3, it’s easy to get a sense of just how sensitive things were then, as every avalanche visible in the clip was triggered by one shot. The Lipalian 3 avalanche starts a bit lower than the one from Saturday, but propagates way skier’s left a bit further down the slope, and is the one in the centre of the screen as the clip ends.

One question that may arise after watching the footage is why was the snowboarder able to ride the slope without incident, and then have an avalanche start when the skier started his descent? We can’t know exactly, but given what is known about the slope and its history this season, a few things are likely. Notice in the video how the boarder makes wide, fast turns the whole way down the slope, and how the skier makes shorter, “jumpier” turns, resulting in more pressure on the snowpack at point of impact. The surface area of the board means it sinks into the snow less than skis, and therefore has less of a chance of hitting the critical layer in the snowpack and starting a slide. With the deeper penetration of the skis, and the greater impact on the snow with the jumpier turns, the chance of the skier hitting a critical layer was greater. The other possibility is that the skier hit a thin spot that was weaker than other parts of the slope, making it easier to trigger the avalanche.

Looking at the photos, it seems as though the skier must have been dragged over all the rocks that are visible. In fact, the skier has no recollection of touching anything other than snow, and stated it felt like he was going over a waterfall. The hard slab conditions that existed on the slope likely kept him up off the rocks, as opposed to softer slab, which would have broken apart and been less supportive. Another close call was with the tree at the bottom of the slope. Trees can often be the culprit for those who suffer trauma in avalanches, but this skier had his feet and skis out below him and was able to have only a glancing blow with the tree.

In the end, were there any decisions that should  or should not have been made leading up to and during this incident? These guys did a bunch of things right – they read the current avalanche bulletin for the area; they skied the slope one at a time; the snowboarder (first person down the slope) went to a safe spot off to the side to watch his partner; the skier yelled out to alert his partner of the avalanche; the skier tried hard to keep his feet in front of him and stay upright during the slide; the snowboarder did his best to keep track of his partner while in the slide; they reported the avalanche to ski area staff. If there was one area for improvement, it would be that they both carry avalanche rescue gear – beacon, shovel, and probe. Had the skier been buried in the debris, his partner would have had no way of finding him. Rescue gear had been discussed in the morning, but a conscious decision had been made to leave it behind since they had not planned to exit the ski area boundary that day.

We can never stress enough how important it is to report avalanches when they happen. The single most critical piece of information we received about this event was confirmation from those involved that there were no other people involved. We were able to call off what could have turned into a huge rescue scenario that would have involved a lot of personnel, equipment, time, and exposure to risk. Many avalanches still go unreported, and every time that’s the case we lose an opportunity to better our understanding and to educate ourselves and, hopefully, the skiing public. Just as we do with those entering an avalanche closure, our policy is always “education over alienation”, which means that we’re more concerned that people take this kind of incident as an opportunity to learn, and less so with criticizing  their choices.

More important than anything, these two survived unscathed an incident that very easily could have turned out much worse.

Lipalian 3 Slope Statistics and Avalanche History (Winter 2010/11)

Slope Stats

  • 38 degree slope angle at top centre of start zone
  • start zone is a WNW aspect
  • start zone elevation – 2460m
  • vertical drop – 150m
  • ground cover – smooth shale
  • bed surface of March 26 avalanche (surface it slid on) – top and skier’s right was November rain crust and facets, lower and skier’s left was older snow surface

Avalanche History

  • Dec. 15, 2010: Size 2.5, similar in size and shape to Mar 26, 50cm average crown depth, ran on Nov crust and facets, sympathetic from heli-bomb in Lipalian 1 (Lipalian 1,2,3 all ran from this shot).
  • Jan 11, 2011: Size 1.5, 10-30cm crown depth, ran on old snow interface (not Nov crust/facets), ran in same feature as Mar 26.
  • Jan 30, 2011: Size 2, all of skier’s right (not the area that ran Mar 26), up to 60cm deep.
  • Feb 14, 2011: Size1.5, failed lower and skier’s left of Mar 26, on old snow interface.


All Back Bowls Now Open

It’s been a busy couple of weeks for the avalanche control team at Lake Louise, but their hard work has paid off with the opening of more alpine terrain. As of this week, Upper ER 5, ER 6, and Elevator Shaft are all open, which means that the only areas still closed are the permanent avalanche closures, which never open.

Elevator Shaft opened shortly after lunch on Thursday, after crews spent the morning blasting the slope and surrounding area with the avalauncher gun located between Marmot and the Rock Garden. Because of the complexity and size of the terrain, and the fact that it isn’t lift serviced, using an avalauncher is much faster than traveling on foot to place explosives on the slope. While crews must still travel in the terrain, the number of overall laps is reduced.

Upper ER 5 opened Thursday as well, but because of a few thin areas on the slope, will be available to ski only on a limited basis. The main areas of concern are the narrow chokes that pass through the cliff bands dividing Upper and Lower ER 5. It doesn’t take much traffic to scrape these down to rock, and limiting the amount of time the run remains open is one way of preserving these areas. It is unlikely Upper ER 5 will open at all on weekends, and weekday openings will depend on amount of traffic and conditions on the slope. When open, the main access is through a gate on the skier’s right, or Paradise Bowl, side of the slope. This gate is visible from Paradise chair, and is at the top of the long straight section of closure fence that runs parallel to the lift. There is currently no access permitted from the ER 6 side.

If Upper ER 5 is closed, skiers craving steep alpine terrain should head over to Whitehorn II, especially over towards ‘F’, ‘G’, and ‘H’ Gullies. Conditions there are superb, and little traffic means that fresh lines are still being found late into the day.


12cm in the Last 24hrs, More Coming…

Once again Lake Louise has received a new coating of snow, 12cm in the last 24hrs. The snow is expected to continue all day Thursday, with the most intense snowfall coming this afternoon. Forecasts are calling for another 20cm today along the divide, so things look great for yet another epic Lake Louise weekend!

 

YES! Snowing at the Lake, March 10, 2011.

 

 


All of Whitehorn II Now Open!

As we all hoped, just after 10:00am this morning (Monday) the hard work of the avalanche control team paid off as the rest of Whitehorn II, from ‘D’ to ‘I’ Gully, opened for the first time this season. Conditions are great overall, with a few of the chokes still a  little “bony”. There’s plenty of deep soft snow to be found, especially below the chokes in the fans. With sunshine and good visibility, today’s another great day to be at the Lake!


Whitehorn II – Seeing the Light of Day

Things at Lake Louise are a far cry from how they were around the new year, when below-average snowfall amounts conspired with weak layers in the snowpack to cause much of our double-black diamond terrain to avalanche, losing most or all of whatever snow had accumulated up to that point. Even after some of the big snowfalls in January, the weak layers persisted and our hearts sank as we watched what looked like a good start slide out to the bottom of the slope. As much as we convinced ourselves that this was a good thing (it is – really!), it doesn’t make it easier.

Why is it a good thing? Well, knowing what we know now about the state of our snowpack, avalanches were the only way of clearing out any weak layers and rain crust that still existed from the early season. The weak layer couldn’t support the weight of new snow on top, and the rain crust from Nov. 9 provided a smooth running surface that allowed snow to avalanche even more easily.

On a typical day in a normal January,  avalanche control teams would spend the first part of the morning controlling terrain that had already opened that season so it could open for the day, and would then move on to still-closed slopes so they could the get the attention they needed in order to have their gates cracked eventually as well. This was no normal January, however, as over 150cm of snow fell during the month, making a huge job out of just keeping open the runs that had already been so. This meant that teams weren’t able to spend much time in the steep back side runs. Constant traffic by control teams using ski cuts and explosives is needed, especially in places like Whitehorn II, which is a large, complex piece of terrain that require significant attention to detail in order to safely rule out avalanches being triggered by skiers.

Looking over to the rest of Whitehorn II from lower 'C' Gully.

When looking up at Whitehorn II from the Boomerang flats, the gully that comes straight down from the visible top of the Summit Platter is ‘C’ Gully, and this is the first full-length gully that you see looking from left to right. ‘A’ and ‘B’ Gullies start lower and to the left, and are also less complex. It’s common that ‘A’ Gully opens with the rest of Rodney’s Ridge, as was the case this season. Only recently, with the increased ability of control teams to get into the area, have more gullies opened. Last week saw a new fence installed down the rib dividing ‘C’ and ‘D’ Gullies, and both ‘B’ and ‘C’ were opened to the public.

The more laps control teams can do in these areas the better, for a few reasons. Obviously, the more ski cuts and explosives teams can deploy the better for slope stabilization. But increased travel also results in increased confidence, as teams improve their knowledge of each of the many little features that make up a huge piece of real estate, and their big-picture view gradually gets filled in by lots of little pictures.

Getting ski cuts into as many places as possible in Whitehorn II.

In a place like Whitehorn II, control teams will use every weapon in their arsenal to give them the confidence they need that the area is safe to open for the public. This includes encouraging other patrollers and trail crew to make laps and cover as much ground as possible, providing valued slope compaction and breaking up any layers that exist in the snow pack. Why wouldn’t we allow just anyone to ski the run and give us the compaction that helps so much? Until avalanche forecasters have the confidence needed to open a run to the public, all traffic must be controlled, and by using staff, we can discuss the routes to be taken and how to travel safely through the terrain, and all staff have radios that can be used for instant communication if needed.

Even with this planned and organized traffic, just because a slope doesn’t avalanche under the weight of one skier doesn’t mean it will hold up when the masses are on it. As one of the last steps in preparing a slope to open, control teams have two related methods of simulating the stress of a large number of skiers on a slope. The first is a “nuke on a stick”, which is two explosive rounds taped together, then attached to the top end of a bamboo placed in the snow, leaving the shots a foot or two above the snow surface. Leaving the shots exposed to the air allows the blast to travel a greater distance and therefore affect more of the slope at once. The other method involves a “Hershey kiss”, which is a shot placed into a bag of ANFO and left on the surface of the snow. The effect is similar to that of the nuke on the stick, but packs more of a punch and can cover a greater distance.

Patrollers make their way through.

Usually the goal of explosive work is to get the shot deep into the snow, so it can test the stability of weak layers that may be buried in the snow pack. The methods mentioned above do not achieve this goal, but they don’t have to , since that type of control work would have happened much earlier in the life of the slope. Buried weak layers are no longer a concern, so the only purpose of these surface blasts is to simulate the weight of a large group of skiers on a slope.

Control teams have made great progress in the rest of Whitehorn II lately, and their hard work is about to pay off as skiers will soon see the opening of most of the rest of the gullies, over to and including ‘G’ Gully. Conditions are great, especially below the gullies in the fans, where snow is deep and rocks are hard to come by. Once control work is completed, all that remains to do is to install a new fence line to divide ‘G’ and ‘H’ Gullies, and it’ll be good to go.

Won't be long now...