Snowfall at Lake LouisePosted: March 5, 2010
There’s no question – snowfall seems to be on the minds of most skiers and snowboarders these days, as in “When is it coming?”. A few of our local forecasts are calling for snow around the middle of next week, but those forecasts are still a few days outside our normal window of confidence for accuracy.
I was asked recently if it was true that Lake Louise tends to get most of its snow in March, and while a positive answer may give reason to hope to powder-starved skiers, that is actually not the case. At the same time, I’ve been here long enough to know that anything can happen, and I’ve seen more than one “miracle spring”, where the skies open up and we ski powder for the last month or two of the season.
As far as monthly totals go, November, December, and January are the three months where we usually see the most snowfall. Since record-keeping began in earnest around 1970, those three months have each seen the year’s most snow 9 or ten times, with March at about 6 times, and February and April bringing up the rear. Since 1970, the season with the most snowfall was 1971-72, when over 540cm fell during the six months of operation. December, January, and February each saw over 1m of snow, with February taking the rare lead in totals for that year. In contrast, February of this year didn’t even come close, with under 20cm total snowfall for a month that averages 50-60cm.
Most people will probably agree that if it’s not going to snow, the next best thing is sunny skies, and there’s certainly been no shortage of those this winter. One could not be blamed for thinking it was April while we were still in the throes of February, as afternoons saw soft slushy snow appearing on south-facing slopes, and hats and goggles were replaced by sunglasses and tans.
Everyone knows that sun and warm temperatures affects the snow surface, but it does so in one way that is less obvious and has important implications with regards to snow stability. Prior to the current run of warm weather, most places in the mountains of British Columbia and Alberta experienced widespread surface hoar – those light feathery snow crystals that develop on the snow surface when the right conditions line up. If they remain on top (in other words, if it doesn’t snow), they’re not an issue. It’s when more snow comes and accumulates on top that stability deteriorates and the avalanche hazard shoots up. The hoar crystals have no strength, and become a weak layer in the snowpack once they become buried. As soon as they can no longer support the weight of the snow lying on top, the layer of hoar crystals collapses, and widespread avalanching occurs.
We didn’t see a significant elevation of avalanche hazard in the Lake Louise area because there was never enough snow on top to create that critical load. In B.C., however, additional snow resulted in conditions becoming so touchy that the Canadian Avalanche Centre has issued three special avalanche warnings in two weeks. The most recent warning, which contains a link to some pretty graphic photos, can be found here:
Now that the sun is hitting some of Lake Louise’s slopes full force, the surface hoar on those solar aspects is melting and becoming a part of the melt/freeze layer that results from the cycle of warm days and cold nights. On north-facing slopes, however, there’s less sun, and the surface hoar still exists and will be an issue when sufficiently loaded with new snow. That lack of solar radiation on north-facing slopes also explains why it’s possible to find winter-like ski conditions well into spring.