Snowfall ReportingPosted: January 24, 2012
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.