17cm Overnight!

Not the 20+cm one forecast was calling for, but I’m finding it hard to complain with another 17cm of new snow overnight at Lake Louise, bringing the weekly snowfall total to 55cm. And with the snow supposed to keep coming for a few days still, there’s going to be lots for everyone!

In addition to snowfall, last night also saw moderate winds blowing for most of the night, which means it’s reasonable to expect some delays in terrain openings. Moderate winds can move around a lot of snow, and with lots of snow available to be moved around (called fetch), we’re expecting slab conditions on leeward slopes. Slab avalanches are usually the largest and most destructive, so control teams will want to make sure they’ve taken care of any lingering avalanche potential before opening avalanche terrain to the public.

Enjoy the powder!

Advertisements

Big Snow for the Lake Tonight?

Don’t tell anyone, but the Lake Louise Ski Area Avalanche Control office subscribes to a weather service that provides detailed daily forecasts specifically for this area, and based on what that forecast has been saying the last few days, it looks promising that tonight may see the arrival of a significant snowfall. One estimate predicts over 15mm of moisture. The rule of thumb at Lake Louise is that 1mm of water equals around 1.5cm of snow, so 15mm of moisture therefore points to over 20cm of snow!

Of course, with any forecast there’s unpredictability, and there are other publicly available sources that call for somewhat more modest snowfall amounts. But we in the ski industry have selective hearing, and ignore those ones in favour of the forecasts that call for big dumps.

Today, the snow really started falling at around 1:00pm, when it was coming down at a rate of 2cm per hour. With this afternoon’s total at 4cm and counting before day’s end, we’re already off to a good start!

Our fingers are officially crossed.


Still Snowing at the Lake!

7:45am, Thursday January 26, 2012:

Yeehaaa!


Whitehorn II

As snow stability and coverage continue to improve in Whitehorn II, the Avalanche Control has decided the time is right to open it all up, side to side, top to bottom. Up to now, just A Gully has been open, but it is treated as a part of the Rodney’s Ridge area, and has no bearing on whether the rest of the gullies open or close. Crews were happy with the way things had set up in the rest of the gullies, and just a little more work was required this week before the gates were cracked for the first time this year.

One significant difference in opening this terrain this year over previous seasons is that the entire Whitehorn II area will open together, rather than one or a few gullies opening at a time as crews move across. This is mainly due to the fact that stability has improved to the point that crews have been able to move quickly and cover a lot more ground than usual, rather than picking their way through every piece of micro-terrain in each gully (there’s a lot of them!). These little areas still need attention, but when snow is sticking to the slope despite the efforts of the control teams to make it avalanche with explosives and ski cuts, confidence in snowpack stability increases as does the ability of the teams to move quickly through the terrain.

One of the greatest tools available to control teams for slope stabilization is skier compaction. Until an avalanche area opens to the public, this compaction is achieved by Ski Patrol and Trail Crew members skiing the slopes. While it could be argued that opening the run to the public would allow compaction to happen much more quickly and thoroughly, we still need to tightly control who goes into these areas and where exactly they go. The Avalanche Forecaster communicates where he wants compaction to happen, and staff are in constant touch with him and each other by radio so the highest level of safety is maintained.

One benefit of opening all remaining gullies together is that crews do not need to place the fence lines that are usually used to separate open areas from closed. This is time-consuming work, and not having to do it in this case allows the terrain to open days sooner than it otherwise would have. There will still be a fence placed between G and H Gullies as in previous years, however, since they have a more easterly component to their aspects, and therefore have greater potential to be affected by the warm spring sun and may need to be closed while the rest of Whitehorn II can remain open.

I took a lap through B Gully on Monday, and even through the choke of the gully conditions were fantastic, and only got better down on the fan below (the ‘fan’ is the area where avalanching snow will spread out and slow down after it passes through the narrow choke). The underlying snowpack was nicely supportive, and the soft boot-deep snow on top was literally the icing on the cake!


Snowfall Reporting

Occasionally we get asked about our snow reports – how we measure, where we measure, and how we track the changing snowpack over time. Staying on top of changes in weather and snowpack in real time is actually a little more challenging than it may appear, due to a number of reasons. I hope now to answer some questions and clarify how it is we accomplish this very important function.

Snow Safety operates two snow plots on the mountain – one near Pika Corner above Paradise base, and the other in Boomerang near the top of Whitehorn III. The plot at Pika, which represents the mid-mountain snowfall amount, has equipment that measures everything from height of new snow to temperature to snow moisture content. The Boomerang plot, representing the upper mountain totals, has stakes to measure height of new snow and height of snowpack. Other than what they’re able to measure, the main difference between the two plots is that the one at Pika is sheltered by trees, and generally gives measurements that are less affected by wind. The Boomerang plot is in an unsheltered location in the alpine, and is much more susceptible to the effects of wind.

Why does this matter? Well, when measuring snow, the goal is to get an amount that reflects only the amount of snow that’s fallen, and not any that may have been blown into or out of the plot by the wind. So, in Boomerang, it could be said that the totals we get there tell us how much snow did not get blown away, and not the total snowfall for that area. This is still valuable information for our control teams, as it is just one piece when it comes to figuring out the complicated puzzle that is the Lake Louise snowpack.

For the Lake Louise Ski Area’s public snow reports, most of our information is gathered from these two plots. These reports, which get communicated by e-mail, fax, website, and phone recordings, are created every day between 5:00am and 6:00am. In addition to the plots, we can contact cat drivers and snowmakers who are working at night if we want more information. If we receive snow during the day, we update the conditions section of our website, but we will not send out more than one set of faxes or e-mails per day. The website always indicates the time at which the update was made, so it’s the best place to go for the most up-to-date information.

The big question we get is why does there so often seem to be more snow than the snow report says there is? For that, once again we can thank the wind, which has a wonderful habit of blowing snow from the windward slopes (usually those facing southwest) and depositing it on the leeward slopes (those facing northeast). In the right conditions there can be up to three or four times the amount of reported snow on leeward slopes. This all depends on the strength and duration of the wind, and how much snow there is available to be transported. Snowfall with no wind will usually result in a consistently deep cover all over the mountain, while the same amount of snowfall accompanied by wind will result in wildly varying amounts in different places on the mountain. As a rule of thumb, there’s usually wind blowing, so the savvy Lake Louise skier will know that our back bowls – the usual beneficiaries of wind-blown snow – will have more than the reported amount.

Finally, we are asked why the year-to-date and the depth of snow amounts are different. If we get 100cm in a month, why isn’t the depth of snow 100cm? A number of things conspire to reduce the depth of snow, but settlement and wind are the main culprits, with temperature joining the mix once the warmer days of spring arrive. As already mentioned, wind can blow snow away. Settlement is the natural process of the snow crystals changing shape and moving closer together under their own weight, and warm weather accelerates this process.

All of these changes in the snowpack are monitored by the Avalanche Control department from the day the first flake hits the ground in autumn until after the mountain closes for the ski season, and help staff gain as comprehensive as possible a picture of the state of the mountain snowpack.


Whitehorn II – D Gully

Blue skies greeted avalanche control teams as they made their way to Whitehorn II yesterday morning to make the first foray of the season into D Gully. With no snowfall in the few days leading up to yesterday, there was little control work required in terrain that had already opened, and crews had the chance to continue work in closed terrain, getting it ready for its eventual opening.

In Whitehorn II, control work always begins at the far skier’s right, at A Gully. This gully, along with B Gully, starts lower than the rest, and is accessed by skiing along the fence line on skier’s left of Whitehorn I toward Rodney’s Ridge, then hanging a left where the fence turns to head down the fall line. Barely recognizable as a gully, A Gully is treated as a part of Rodney’s Ridge, and has been open for most of this season. Control teams will always leave a buffer next to open terrain – in this case, B Gully. In other words, for A Gully to open, B Gully needs to be controlled, too.

As one gully opens, teams move to the next, and so it goes until all of Whitehorn II opens. Yesterday marked the first control efforts in D Gully, and the start of a long process of control for a piece of terrain that is steep, complex, and, in addition to the main pitch of the gully, contains a few smaller cells that have characteristics all their own. This is true of all Whitehorn II gullies, and many rounds of explosives, bootpacking, and ski cutting are required to get the area ready to open.

D Gully has the largest start zone of all Whitehorn II gullies, and a number of explosive shots were used in this area. A start zone is where the bulk of wind-loaded snow usually ends up, and is therefore where most avalanches start. Two types of explosives were used – the usual dynamite-style charges, as well as bags of ANFO (ammonium nitrate & fuel oil). The smaller charges are thrown onto the slope and ideally will penetrate the surface layer so that the explosion has a better chance of reaching deeper into the snowpack, which is where the troublesome layers usually exist. On big slopes where the desire is for an explosive to cover a much greater area, ANFO is the ticket, as each charge can be built bigger or smaller depending on the wishes of the avalanche forecaster. The one used yesterday, for example, was about 7kg and packed a much larger punch than the usual hand charge would have, both outward and downward. If a slope doesn’t avalanche after an ANFO shot or two, control teams have that much more confidence in the stability of the slope and their ability to move safely on it, especially in the earlier stages of control work.

Prevailing winds generally blow across the slope from the skier’s left, which means that half of the gully will have more snow and therefore a greater potential for avalanches. With this in mind, five of us made our way down the right side, using ski cuts as we moved and stopping often to throw explosives on the left side. Happily, none of the shots produced significant results, which bodes well for the continued improvement of the slope. Much more work is needed, but good progress has been made, and every lap control teams make gets us closer to opening and having it available for all to enjoy.


Happy New Year!

NOTE: This post has been edited – it originally stated that ER6 was opened, when in fact it was not, and hasn’t yet opened this season. Crews are working at getting it ready, and I’ll let you know when it’s good to go – sorry for the mistake!

A happy new year indeed! After an incredible few weeks of fantastic weather – lots of snow, blue skies, warm temperatures – skiing at the Lake is about as good as it gets. We’re getting close to having all of our terrain open, and we’re proud to start the new year by adding the Big 7 area to the list of open runs. The ER7 gullies have been open a few days now, but the rest of ER7, including Big 7 and Vertical Cornice, followed suit once control teams were satisfied with that area.

2012 started a little on the cold side, but also with clear skies, and skiers who braved a day on the slopes after a big night out were rewarded with that million-dollar view that the Lake is famous for. We’re always happy when the holiday season experiences good weather and conditions, as many of the people visiting that week are first-timers, and what better way to get them to leave with a great first impression than to experience Lake Louise at its finest. Of course, it doesn’t hurt us that many ski areas, in North America and in Europe, are experiencing low snowfall and decidedly less-than-ideal conditions.

As for our snowpack, things are certainly looking up – not only from the amount we’ve been getting, but from a stability standpoint as well. After a series of big avalanches (both natural and the result of control work) cleaned out much of Whitehorn II for example, we entered a phase of rebuilding, when the slopes start over and we all hope that the snowpack can build without any weakness or instabilites. That seems to be the direction in which things are headed at the moment, and while there isn’t enough snow yet to allow skiing, what is there is sticking to the slopes, even after explosives are used.

Some areas not that far from here are seeing a buried surface hoar layer from mid-December that is causing some concern, but for the most part we aren’t seeing that here. This past week, control teams from Parks Canada were using large bags of ANFO (ammonium nitrate and fuel oil) thrown from a helicopter to control the slopes on Mt. Bosworth, which overlooks the Trans-Canada Highway between Lake Louise and Kicking Horse Pass. Their efforts resulted in numerous size 3 avalanches, all running on this buried surface hoar layer, and in some cases stepping down to lower layers in the pack.

For now, avalanche control teams will continue the charge, controlling slopes that have already opened and getting into slopes that are still closed, preparing them for their eventual opening.

Throwing a shot in BOOB (Beyond Out Of Bounds). photo: Rocket Miller