James Montanus has seen his fair share of interesting sights living on the shores of Lake Ontario, but the cloud formations he spotted Tuesday resembled something from another planet. The Rochester, N.Y.-based photographer captured a mesmerizing display of undulatus asperatus, or “asperitas” clouds, appearing as undulating wisps against a stormy gray backdrop.

The eerie clouds resemble tempestuous fingers reaching east across the sky, heralding light rain that developed Tuesday afternoon.

The clouds formed along a cold front, the same that has been sparking severe weather, including damaging winds and a few tornadoes, as it trekked east across the Lower 48.

“My girlfriend actually pointed out the clouds to me, so she deserves most of the credit!” wrote Montanus in a Twitter direct message early Wednesday. “When I saw the clouds I knew they were special. I was literally running around in my house in a panic looking for my camera.”

Montanus described the day’s weather as “changeable,” reporting alternating periods of intermittent sun and rain.

“Moments of sun through light clouds, and then it would be cloudy,” he wrote, “but the weather in general was interesting all day. It kept me looking up.”

Asperitas clouds are rare and cherished by skywatchers and cloudspotters. They form when the low- or mid-levels of the atmosphere are stable, allowing air to settle in horizontal layers. A nearby perturbation disturbs those layers, sending wavelike ripples through them. When multiple perturbations overlap, the resulting interference pattern can bend previously flat layers of cloud into wonky, wavy patterns.

Imagine cannonballing in a pool. Once you hit the water, waves — or a splash — radiate outward in circles. That’s analogous to local pockets of air moving up or down in the atmosphere and inducing gravity waves, as is common in the vicinity of thunderstorms. If multiple people leaped in the pool simultaneously, however, turbulent wavelike motions would sculpt the surface of the water into chaos.

Instrumental to Tuesday’s show was an inversion, or an increase in temperature with height. A shallow layer of cool air was present near the surface, the trifling surface layer thin enough that gravity waves riding along its upper interface with milder air above contorted it into a strange form.

A morning weather balloon launched out of Buffalo sampled the inversion. At ground level Tuesday morning, it was 48 degrees, but at 2,270 feet, the temperature was 54.3 degrees.

Another key finding — the dew point, a measure of how much water was present in the air, at 2,270 feet was greater than the surface temperature. In other words, any of the inversion air cooled to surface temperatures would become instantly saturated, forming a cloud.

That’s what formed the clouds where the two air masses came into contact, the mild, moist air stacked atop cooler and drier air.

As soon as Montanus saw them, he knew he was witnessing something special. He rushed to share it with others.

“I canceled the bicycle ride I was about to go on so I could edit the pics and get them out on social media as soon as possible,” he wrote.

Montanus, who has spent years photographing the skies over Lake Ontario, says that, while the asperitas clouds were neat, nothing can beat the aurora borealis, or northern lights.

“The most amazing things I have captured are beautiful displays of the northern lights over Lake Ontario,” he wrote. “This is rare at our latitude, but it does happen. And when it does, it’s a rush.”

He says he also captured a seiche — or a weather-driven tsunami-like wave that can be several feet in amplitude. Lightning is a favorite of his, too.