Clouds can often be a pretty inconsequential part of a weather forecast from the public's perspective, compared to temperature and precipitation.
But on Monday, cloud cover could be what stands – or floats –between the solar eclipse and throngs gathered along the path of totality in Canada.
"Let's just say that cloud cover is not the reason why meteorologists get into the profession," Gerald Cheng, a meteorologist with Environment Canada, said in an interview.
Cheng joked that he was "totally reluctant" to make specific predictions for what eclipse watchers could expect to see during a narrow window of time come Monday afternoon.
That's because weather forecasts can be fickle, he said.
A cloud cover prediction four days in advance, stretching across six provinces, in a brief window of time "can be really off," he said.
But with those caveats in mind, here is a brief preliminary forecast for Monday, along the solar eclipse's path of totality.
Ontario
In a sign of just how quickly things can change, Cheng said the forecast for southwestern Ontario shifted over the course of a few hours on Thursday.
Around noon, he said the Niagara region and areas along Lake Erie's shores were likely to see blanket cloud cover. But three hours later he updated that forecast to say it could be mainly cloudy, to a mix of sun and cloud.
It appears as though there could be patches in the cloud cover, he said.
"You may be lucky to get a break in there."
Moving into eastern Ontario, around Kingston and Cornwall, Cheng said conditions appeared to be slightly better, but still favoured clouds.
Quebec
The forecast is looking favourable for Quebec regions in the eclipse's path, Cheng said.
"It seems like the best, according to our official forecast and looking at the information I have," he said.
Cheng said come Monday it "should be sunny" in Montreal and Sherbrooke, based on what he could see.
Newfoundland
A low-pressure system is threatening to spoil the eclipse for watchers in Newfoundland.
Cheng said the offshore system, set to develop off Nova Scotia and move into Newfoundland, could bring "a lot of cloud cover" on Monday.
While he called the area around Gander basically "a writeoff," he said clouds could start to break on the southwestern tip of the island.
"When we deal with offshore systems, there's a lot of uncertainty because there's not a lot of observations, so you always have to check back and see if the system is close or not close," he said.
New Brunswick, Prince Edward Island and Cape Breton, N.S.
That same low-pressure system was generating some uncertainty in the forecast for the Maritimes, said Cheng.
Cheng said "it could be a mix of sun and clouds" for parts of New Brunswick, through Prince Edward Island, the tip of Cape Breton and into the Quebec archipelago of the Iles-de-la-Madeleine.
"That's really a mix because the system is leaving," he said. "It depends on the speed of the system."
This report by The Canadian Press was first published April 5, 2024.
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