DAYTON — Dayton caught a break from the breeze Thursday, May 20, when a towering plume of smoke erupted from the fire at Franklin Iron & Metal Corp. on First Street.

Atmospheric conditions initially kept the plume lower to the ground, filling up low areas with choking smoke. Until the sun heated the air by late morning, the smoke merged with foggy conditions and created haze throughout downtown and beyond.

A condition of cooler air close to the ground that is trapped by warmer air above is known to meteorologists as an inversion. That’s what happened Thursday morning according to readings from a weather balloon released by the National Weather Service in Wilmington, said meteorologist Andy Hatzos. Had the sun taken longer to come out, conditions could have been worse, he said.

Fortunately, winds came from the south and southeast during the day, carrying the plume over an industrial/commercial area to the Mad River and in the direction of Children’s Hospital, which is a half-mile from the fire’s center, said Brian Huxtable, air pollution control specialist with the Regional Air Pollution Control Agency, or RAPCA.

The distance allowed the smoke to dissipate before hitting residential areas. Throughout the day, the smoke showed up in the Old North Dayton neighborhood as a light haze.

A wind blowing from the northwest could have carried the smoke directly into East Dayton neighborhoods, a block or so away from the fire. Firefighters were on the alert for any wind shifts.

Generally speaking, prevailing winds are from the southwest to the northwest, said Hatzos. Southeast winds “are not so common.”

So, Thursday at least, weather spared the city.

WHIO-TV chief meteorologist Jamie Simpson added that had the fire raged throughout the night, another inversion could have trapped the smoke. “Thankfully, they had the fire in hand,” he said.

Contact this reporter at (937) 225-7407 or sbennish@DaytonDailyNews.com.