The smoke from the massive mill fire in Mechanic Falls was so dense and elongated, it was picked up on Doppler radar Sunday afternoon.

Jessica Conley first noticed this while in South Portland. The plume of smoke extended horizontally across the sky, stretching from Mechanic Falls to the coast.

New technology introduced in the last couple of years, through Dual-polarization radar, allows us to see the size and shape of targets hit by the radar. Low correlation coefficient values (right panel above) confirm the radar was picking up on something other than precipitation falling from the sky.

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The smoke was seen for miles because it didn't rise vertically. Instead it was moving horizontally. That’s because of a temperature inversion, or warmer air a couple thousand feet above the ground.

As the smoke went up, it’s became less buoyant, and couldn't rise through the layer of warmer air. It was trapped, and then slowly spread out from west to east as the wind picked it up.