Colder-than-normal temperatures across B.C. mean hydrologists and meteorologists are watching the coming days very closely.
A cold spring throughout the province resulted in temperatures being 1.5 to 4.5 degrees below normal for April.
Jonathan Boyd, a hydrologist with the River Forecast Centre, says some people might think this means B.C. is salvaged from flooding for this time of year, but that's not the case.
"I’ve heard that and I would say from my point of view, it is really the opposite,” he tells Glacier Media.
"This is really a worst-case situation.”
Historically speaking, the years that had the greatest flood risk had cold temperatures in April and early May, he says.
"What that does, instead of having the mid- and low-elevation snow start to melt, it sticks around a little bit longer. By that point... if there is a scenario where there is a hot high-pressure ridge heat wave event that lasts for five to seven days, then you have all the elevations melting snow simultaneously.”
Boyd says the risk of that happening has significantly increased from April to May 1. A simultaneous snow melt would result in rivers rising rapidly, he notes.
An ideal situation would be warmer temperatures for a short period of time (a day), and then a cooling-off so the melt can happen slowly and not all at once.
Doug Lundquist, a meteorologist with Environment Canada, says temperatures don’t appear to be warming up significantly any time soon.
"The fact that it is cooler and wetter lately is good for fires. ... That can cost us millions and millions of dollars and trouble. That is a good news story, to have spring a little wetter is a good thing."
Adding: “We do rely on June rain so if it does dry out in June... then we could be in trouble, yeah. We need to know what happens in June for fire weather.”
In regards to the freshet and flooding, he says the cold weather is a concern.
"I don’t want to see it really warming up too too fast. I don’t want to see any heavy rains coming up. This is the kind of thing I am concerned about. But for the next 10 days, I don’t see any of that.”
Where in B.C. is most at risk?
If temperatures peaked and got high for multiple days, Boyd says a lot of areas in B.C.’s Interior would be at high flows.
"The rain can also add to the challenges, especially if a heavy rainfall event occurred after a heat wave on snow that was already melting,” he says. “It can melt it at an even faster rate combined with the added water from the rainfall itself.”
Areas in the Interior, Upper Fraser, North Thompson, the Cariboo region, Upper Columbia, parts of the East and West Kootenay are all above normal snow pack and in some cases pretty substantial above normal.
"Not necessarily record snow pack, but that sometimes is the sneaky year, where the snow pack is a little bit above normal and gets people’s false sense that there isn’t a risk, that we can sometimes get troubling flows later on.”
Boyd says the climate conditions this year have not been normal and having six weeks of straight below-seasonal temperatures is concerning.
"It really is just at the mercy of Mother Nature to see what happens,” he says.
Severe thunderstorms also a concern
There's another significant risk Lundquist is watching for.
"My biggest concern between now and mid-August or even till September is if we get severe thunderstorms,” he says. “If it happens to land on a burn scar or one of these areas that has been burnt out, it is going to cause problems.”
Having a severe thunderstorm from now until August could potentially cause flooding or flash flooding, specifically in areas that have had wildfires.
"There won’t be much warning,” he says.
Lundquist urges people to keep tabs on weather alerts. Having an emergency kit handy doesn't hurt either.
New in 2022, the Alert Ready cellphone alerting system will be used for floods and wildfires. In past years, the system was only used for tsunamis and amber alerts.
An updated flood risk forecast is expected to be released on May 20 with data up to May 15.
