PITTSBURGH (KDKA) – A blast of snow came down last night on Interstate 79 on Tuesday evening. It left about an inch in parts of Allegheny and Beaver counties, but this was not your ordinary snow.

It was really man-made snow – a freak storm caused by the nuclear power plant in Shippingport.

A pot of boiling water thrown over a balcony in Siberia crystallizes and instantly turns to snow. That scientific experiment is, on the most basic level, what happened Tuesday night.

Hot steam from the Beaver Valley Nuclear Power Plant combined with near-zero temperatures.

“The warm moisture source from those cooling towers interacting with the cold artic air that’s in place across Western Pennsylvania generated this snow shower, this snow band that lasts for about three hours,” said Fred McMullen, a National Weather Service meteorologist.

And snowy conditions are the effect people south of the Butler County line and in parts of Allegheny County, like Wexford and Gibsonia, saw.

McMullen says it’s a pretty special sight.

“Yesterday was unique because there was nothing else on radar,” he said. “These conditions happen more so than we see; it’s just masked within a larger area of precipitation that covers the radar screen.”

Don Ford, a local resident who has been near the Beaver County plant and seen crystals form before, says it makes sense.

“Just driving through here and it was just like a quick snow squall,” he said. “And by the time I got home, which is only a mile down the road, I didn’t see it anymore.”

McMullen says if you saw the snow generated from the power plant; consider yourself lucky as this specific kind of event only happens every three to five years.

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