Wildfires predicted as floods recede

AccuWeather’s annual Canada summer forecast uses past weather to predict this year’s outlook. Examining past summers influenced by similar climatological conditions allows forecasters to piece together the atmospheric jigsaw puzzle of how the weather may unfold across Canada this season.

The overall forecast trend of near- to above-average rainfall this summer should help prevent fuels from becoming tinder dry. In addition, humidity can also be an inhibiting factor in the growth of wildfires.

While portions of western Canada are expected to encounter near-normal temperatures and near- to above-average rainfall, that will not be the case for other parts of the country.

“Ongoing and worsening severe drought across southern Alberta and southwestern Saskatchewan will likely feed the heat through the summer,” said Brett Anderson, the senior meteorologist who spearheaded the seasonal outlook.

According to the Canadian Drought Monitor, almost all of the southern portions of Alberta and Saskatchewan are experiencing abnormal dryness.

Dry ground is able to more easily radiate heat from the sun back into the lower levels of the atmosphere. This process raises the air temperature to a level several degrees higher than if the soil was moist.

For parts of the prairies, the continued dryness and increasing heat will also spell another danger — wildfires.

“These dry and warm conditions will likely lead to a higher risk for large, rapidly-spreading fires across the southern prairies,” Anderson said.

The exceptions to this elevated heat and wildfire risk — at least in the early summer — are likely to be portions of southeastern Saskatchewan and southern Manitoba.

“The soil in these areas is still quite moist, with river flooding ongoing given recent rounds of heavy storms,” Anderson said.

He said that when soil is too moist, it can present problems for farmers attempting to plant crops, but increased moisture may deter the potential for above-average heat through the early summer in the eastern prairies. Anderson said he doubts this buffer will last the whole summer.

“Conditions may flip to drier and hotter during the second half of summer as the soil dries out,” Anderson said.

As was the case for the winter and spring, a moderate La Niña phase is expected to persist into the summer.

During a period of La Niña influence, western Canada is typically the portion of the country that experiences the most significant impacts. La Niña is one of many teleconnections meteorologists study to determine weather outlooks on a seasonal scale. Teleconnections are essentially a correlation found between meteorological phenomena located a great distance from one another.

“Given current conditions and the teleconnections expected to be in place, we may see a reduction in fire activity this year, especially when compared to last summer,” Anderson said.

With an under-abundance of fuels like dry grass or dead plants, the chances of wildfires developing are reduced.

In addition to the expected levels of rain for much of western Canada, the water flowing at ground level is also set to be in a good position this summer.

“Rivers and streams should continue to run near to above normal with ample runoff from a significant mountain snowpack,” Anderson said.

A deep snowpack — a layer of snow found in mountainous areas — is key during the coldest months of the year. Runoff from this snowpack works its way into rivers and streams and keeps water flowing to many locations throughout the province during summer.

In terms of temperatures this summer, AccuWeather forecasters say anyone in western Canada dreading a repeat of last year’s brutal heat may be able to breathe a bit easier this year.

Anderson said he expects air temperatures will be near normal for much of British Columbia, as water conditions in the Canadian Pacific are expected to be cooler than normal.

In the east, AccuWeather forecasters say wet and stormy weather will be common this summer.

Anderson has isolated a swath in eastern Canada extending from central and southern Ontario through western and southern Quebec as an area that will encounter above-normal precipitation and thunderstorm activity this summer.

“This may be a busy summer in terms of severe thunderstorms, especially from the Windsor to Toronto to Ottawa corridor,” Anderson said.

While stormy conditions may put a damper on summer plans, increased amounts of precipitation generally lead to lower overall drought risk.

“The risk of sustained summer drought in this region appears to be low at this point, with many areas set to experience near- to above-normal rainfall,” Anderson said.

With this influx of extra moisture, Anderson said he believes the upcoming summer will be more humid than usual.

“Increased humidity will lead to warmer nights when compared to normal, while temperatures during the daytime will be closer to normal,” Anderson explained.

With more water vapour in the atmosphere, the air closer to the surface is unable to cool as quickly as if the air were drier.

In major cities, the “urban heat island effect” can further worsen conditions — big cities often trap more heat given the sheer amount of paved or built-up surfaces in the area. These building materials are very slow to release the heat and cool down.

Humid conditions are also in store for Atlantic Canada, according to Anderson. Not only will humidity build, but given forecast trends in water temperatures around the region, this summer is likely to be warmer than normal.

“I expect water temperatures to average about 1-2 degrees above normal in the Atlantic, off the coast of Nova Scotia,” Anderson said. “This will have a warming and higher humidity influence on the surrounding area, especially at night.”

Rainfall amounts for the area this summer are expected to generally be near normal for much of Atlantic Canada, but Newfoundland could be the exception. Newfoundland may end up recording below-average precipitation, according to Anderson.

As the summer progresses, all eyes will likely shift to tropical activity. For residents of Atlantic Canada, Anderson sees some worrying trends.

“Based on La Niña and the projected higher-than-average Atlantic water temperatures, there can be a higher-than-normal risk for a landfalling tropical system in Atlantic Canada,” Anderson said.

AccuWeather forecasters are calling for another highly-active hurricane season in the Atlantic basin in 2022.

The timing for this increased risk would largely be late summer and into early fall.