Well, it happened again.

About 8:35 Tuesday morning, a large radar disturbance glittered across weather maps in Southern Indiana. The wispy green blob stretched from Evansville all the way to Terre Haute in the north and as far east as Franklin.

It made it look as though a light rain blanketed a big slice of the state. Problem is, it didn’t rain at all on Tuesday.

WEVV Chief Meteorologist Cameron Hopman posted a GIF to Twitter. As the timestamp dragged from 8:35 to 10 a.m., the disturbance dissipated up north but grew over Evansville, twisting into the shape of a small hurricane. He asked the National Weather Service out of Paducah, Kentucky, if they had any answers.

I gave NWS a call as well. The last time a strange radar blip hit the Tri-State, the culprit was allegedly chaff: tiny metal particles of radar-jamming material sometimes released by military planes.

This time, however, the explanation was different.

The NWS’ Michael York blamed Tuesday’s disturbance on “anomalous propagation” – false echoes in the radar caused when the radar beam, which usually shoots into the atmosphere, aims downward.

It often happens when the atmosphere is at its calmest. And it occurs during a temperature inversion — when the atmospheric temperature is warmer than the ground temps.

What looked like rain on the map was actually the radar picking up “ground clutter,” York said, such as trees or anything else that might be lying around.

If you watch the GIF, you’ll see a second odd occurrence: a skinny squall line that shoots through Southwestern Indiana.

“That’s somewhat unusual. Sometimes we get thunderstorms developing on them if (the weather) is unstable,” York said. “But at that time of day, it was stable.”

This marks the second time in nine months a weird radar blemish has dashed across the Tri-State.

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Back in December, a harsh line of storm-looking radar blazed through Western Kentucky and Southern Illinois. In that case, Eyewitness News Meteorologist Wayne Hart cited an unnamed pilot who said a military C-130 had spewed chaff – radar jamming material – during a training exercise.

When I called area Air Force bases, though, none of them knew anything about it.

Eventually, the aviation blog The War Zone got hold of Captain Holli Nelson of the West Virginia Air National Guard, who said one of her planes fired chaff over the Midwest as it returned from a training exercise out west.

For safety reasons, the plane had to release the stuff before landing, she said.

The U.S. military has used chaff at least since World War II. The tiny metal particles muck up radar and help warplanes sidle up on unsuspecting enemies.

When we last published stories about this, though, a flood of emailers shouted B.S., pegging the real culprit as everything from chemtrails to aliens.

Others were even more adventurous. One man said the radar disturbances stemmed from government efforts to control the weather. Private enterprise was involved, too, he said, claiming Bill Gates was experimenting on people as part of an effort to further “global dimming” – a cooling counteraction to global warming.

One questioned whether I was a government agent, and asked if I wrote the story to trick people into emailing me so I could collect their information.

I don’t think I’m a government agent, but who knows? The world would be a much more interesting place if all those things were true.

One thing you can’t dispute is that radar disturbances have been popping up with strange regularity the last few months.

Bizarre blobs materialized over Maine, Florida and Australia. Officials claimed chaff was the official cause in all those cases.

York dismissed the possibility that chaff was to blame on Tuesday.

“It looks completely different on the radar,” he said.

It moves in a line, wind pushing it across the region. Ground clutter, though, plays by its own rules.

So do aliens. Unfortunately, they didn’t visit Tuesday. Maybe next time.

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Contact columnist Jon Webb at jon.webb@courierpress.com