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  • Colorado fires and Canadian flooding–connected?

    Fri, July 12, 2013 by Ryan Handy with no comments

    The short answer is: Yes, and no.

    This morning, I read in the “Rocky Mountain Outlook” an article that connected Colorado’s June wildfires to massive flooding in the Canadian province of Alberta. It seemed a bit far-fetched, but intriguing.

    Colorado fires themselves did not contribute to Alberta flooding, but both were (ironically) caused by the same weather system, said Dr. John Pomeroy, director of the University of Saskatchewan’s hydrology department.

    Here’s what happened:

    In early June, as the Black Forest fire was raging just outside of Colorado Springs, a high-pressure cell was over Colorado, making conditions hot and dry–prime weather for a firestorm.

    “When you get a high pressure cell, it’s very dry air and it tends to be sunny, then you have warm and dry conditions,” Pomeroy explained. “When you get in a long term drought it’s often high pressure for a long time.”

    This cell moved north, and right around the Montana/Alberta border it became trapped in the Rockies, where it rose, cooled, and eventually moved into Alberta, where it dumped the moisture it had collected from Colorado. This effect is called a “cold low.”

    While Colorado was desperate for rain, Alberta was desperate to get out of it.

    “It was raining an inch an hour for quite a while,” Pomeroy said. “The total rainfall was 10 inches over two days. Then we had snow-melt that contributed to another 10 inches of water.”

    It was also cold in Canada–towards the end of the rain-burst,  the storm turned into snow.

    “The moisture was actually getting suck out of Colorado,” Pomeroy added. “So it was the moisture that you would have liked to have had.”

    Cold lows are typically what cause flash-flooding in Colorado in the  summer, when the monsoonal flow becomes trapped in the mountains, and ultimately have all their moisture squeeze out of them. This storm set up was hovering over Colorado in June, but “it was probably pushed out by  the high pressure cell” that was adding heat and dryness to fires, Pomeroy said.

    “It was kind of strange that it moved this far more.,” Pomeroy said of the storm. “We were getting Colorado’s weather.”