Flood risk slight, April showers ahead

By Tim Kalinowski

While the winter has seemed longer and more snowy in southern Alberta than usual, Ralph Wright, head of Alberta Agriculture and Forestry’s AgMet unit, says this year’s winter precipitation levels are actually pretty much right at the long-term average for the region.

“For the most part we have seen near normal to slightly above normal precipitation over the winter,” Wright confirms. “We have seen slightly above normal through the Milk River ridge area, and in some pockets scattered between Lethbridge and Medicine Hat.

“But what has really made it unusual this year is a lot of that snow stuck around because it has been colder than normal. That makes it appear to most people they are having more snow than normal.”

Wright also acknowledges there may be some possible anxiety about flooding, given the lingering snowpacks in certain areas, but feels it is too early to be unduly concerned.

“There is plenty of time to get more snow, and more rain,” he emphasizes. “Also, on the other side of the coin, it could just dry up tomorrow.

“Typically in southern Alberta it’s not one thing which leads to flooding. When you have back to back events that go through the May/ June period, you can get a very large event where you can get 100 mm in a few days there, and sometimes that will cause flooding and sometimes it won’t.

“It really depends on what happens with how dry the landscape is. It can also be whether or not there is a lot of rain on the snowpacks up in the mountains, or if they are very deep.”

Often southern Alberta floods, in some ways, originate in the high mountains, states Wright, but this has to be in conjunction with lingering low pressure systems which drop excessive amounts of rain.

“Many of the mountain snowpacks are showing above normal,” he admits. “The mountain snowpacks are good, which is generally good, right? They need to store water, but we can’t speculate on how it is going to melt out.

“You could have a quick melt, but if you look out over the medium term forecast the weather is still staying a little below normal. That’s probably best to ensure you get that slower melt.”

On the bright side, the deepest lingering snowpacks in southern Alberta, as of the end of March, were in the areas worst hit by the 2017 drought, says Wright.

“The moisture story in southern Alberta starts about June 15 last year,” he explains. “What happened is people down there had a relatively good spring last year and then it dried up significantly. That really brought soil moisture levels down, particularly in a wide band between Calgary and Lethbridge.

“Vulcan County was probably one of the driest areas,” he adds. “They went into the winter very dry; so the near normal to slightly above normal snowpacks have certainly helped turn things around a little bit. It is good because there will be more moisture readily available for when people want to plant.”

Wright says a drier winter chill may linger in the air until about mid-April, and then, based on the long term averages, people should be prepared for the taps to turn on again.

“The spring rains are just around the corner,” he states. “Lethbridge country typically starts seeing that shift into wetter weather about April 12. And there is a marked shift at the end of April, about April 26, into wetter weather.”