Our “What to KNOW before you Go” page stresses the importance of having a good handle on the weather you’re going to encounter while adventuring. Here’s some more information on getting better at weather forecasting.
We have a small bit of expertise in this area. We taught the weather section of the ground school for student glider pilots held in Calgary alongside Steve Rothfels. He not only played a weatherman on TV before retiring, but was actually a meteorologist. We also forecasted the weather for numerous regional and national soaring championships.
Why is forecasting K-Country weather hard?
The trouble with forecasting K-Country weather is simple. Most of it is mountains, and mountain weather forecasting is a challenge. Mountains make their own weather.
Environment Canada generates about 90% of their forecasts using computer models. As one EnviroCan forecaster said to us a number of years ago, “the computers haven’t figured out the mountains are there” (they’re better now, but not much). Of particular issue are air masses that move in from the northwest associated with low-pressure centers (read: storms). These are more common in the summer than the winter due to jet stream positioning. They are a good illustration of the computer problem. While air should drag behind them, and the models model it that way, the mountains cause the air mass to bend in front and around them. The associated weather is not as predicted.
Have you ever noticed that the weather at Lac Des Arcs is often… strange? That’s where the air masses in the mountains meet air masses from the prairies. Funny things happen at air mass interfaces. Temperatures can rise or fall 10° C in the space of a kilometre. It can be raining or snowing there when it isn’t in 5 km in either direction. This isn’t modelled.
Orographic effects
As noted, mountains make their own weather. Most people understand the concept of orographic precipitation — precipitation created when an air mass hits a mountain and has to rise up and over it, simplified above right, and seen clearly on Pigeon Mountain at right.
But mountains are full of microclimates, which aren’t modelled either. Just look at snow at ski areas as an example. Nakiska doesn’t get much snow. Fortress, just down the road, gets more than double the precipitation of Nakiska. Sunshine sits on the divide and gets 30% more snow than Louise, and 50% more than Norquay. Fernie sits in the confluence of 3 valleys and frequently gets hammered with snow.
Solar effects
Put a little sunshine on some exposed rock in the mountains and you can develop thermal heating even in the dead of winter. This results in swirling winds on an otherwise calm day. These can pop up to isolated showers or snow squalls when no precipitation is forecast. If the airmass is even slightly unstable, this can make thunderstorms appear out of nowhere and disappear just as fast. Cold air is heavy and dense and it sinks (creating “katabatic winds”). Theses winds fill valleys with chill air while it can be much warmer up top.
Not what EnviroCan forecasts
And EnviroCan models none of this, because generally they don’t care. That’s not crass, nor a slight against EnviroCan, it’s just not their mandate. EnviroCan tries to model population centers, and people don’t live at the tops of mountains.
What does live up there is airplanes, and EnviroCan cares a lot about them. So EnviroCan actually does an awesome job of forecasting winds aloft and high-level cloud. Bet you didn’t know this, but EnviroCan’s weather radar show precipitation that planes could run into, NOT precipitation that will hit the ground. We’ll discuss more in a later page. In the summer (and winter, to a lesser extent) you’ll often see areas of virga painted on the radar. Virga is the name of precipitation that doesn’t ever hit the ground (due to evaporation, or rising air that sucks it back up). On another page, we’ll delve into the radar issue in more detail.
Special areas demand special forecasts
So EnviroCan isn’t trying to forecast the weather for mountain regions. In the shoulder seasons, they’ll report freezing level (data of high quality, because pilots care about that). But generally, they’re not that useful if you want the answer to the question “What’s it going to be like on Tent Ridge today”? We should mention that EnviroCan has a commercial section that will do custom forecasts for anyone who pays them. That’s usually good data, because the guys who work there are good. However, we’re not aware of anyone who currently pays EnviroCan for custom forecasts; some ski hills used to.
So if EnviroCan doesn’t make K-Country forecasts, who does? Head to the next page in this series to find out!