A rare cloud formation has amazed onlookers and captured the Internet’s attention after appearing over a Virginia lake on Tuesday.

Amy Christie Hunter says she was relaxing on her deck at Smith Mountain Lake around 8:30 p.m. when she spotted what’s called Kelvin-Helmholtz Waves making their way through the evening sky. She says a storm front had been moving through the area.

“I noticed [the clouds] forming and just couldn’t believe it. I grabbed my iPhone to snap a couple of shots and then it crashed just like a wave. My jaw dropped!” Hunter, 59, tells PEOPLE. “A few minutes later a rainbow appeared, so Mother Nature was putting on a show that evening!”

The string of clouds appeared perched on the mountaintops, separating the green mountains from the gray sky above. Hunter says she sent the photo to her local news station, where a meteorologist told her that the clouds are “very rare and usually not this defined.”

“It’s been pretty mind-boggling really. I’m just lucky I got to see it!” she says. “The cloud formation was truly amazing, I couldn’t believe what I was seeing. I had no idea there was a scientific name for it.”

© Amy Christie Hunter Kelvin-Helmholtz Waves over Virginia’s Smith Mountain Lake

The “vertical waves” are associated with rapidly changing wind speeds and directions, according to the National Weather Service.

The cloud “can appear as breaking waves and as braided patterns in radar images and cloud photos,” the NWS says.

Hunter shared the photo on Facebook in a Tuesday post that has been shared nearly 1,000 times. She says it has been shared hundreds of more times in other social media posts.

“I knew it was very unusual and that people would enjoy seeing it. That is why I shared it in the first place,” Hunter tells PEOPLE. “So I had no idea at all it would get so much attention, much less going viral like it has. It was quite a surprise, to say the least. I am pretty stunned that it has ‘gone viral’ as they say!”

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