LOUISVILLE, KY (WAVE) – There has long been proof that human activity can affect the weather. From air pollution to urban heat islands to increased humidity near farms, we humans consistently influence the world around us. But are our planes and industrial plants causing more snow? In a word: yes.

There have been quite a few documented instances of power plants creating and enhancing snow. Another one of the most recent occurrences happened in Nebraska. On the morning of December 3, steam from 2 plants in Norfolk pumped moisture into the atmosphere dumping up to an inch of snow downwind from the plant.

This phenomenon continued into the morning of December 4 where the plume drifted towards the Omaha Metro area, causing light snow and patchy freezing drizzle.

So why does something like this happen? Snow forms when water vapor sublimates onto ice crystals in a cloud. Since clouds are usually a mixture of supercooled water droplets and ice crystals, the ice crystals will grow at the expense of the water droplets. The snowflakes continue to grow through the additional accumulation of supercooled water droplets or by clumping together. Eventually, the snowflakes fall.

Steam from power or industrial plants rises into the atmosphere and evaporates, providing additional moisture to help with snowflake growth. As we saw in WAVE Country on Tuesday, January 15, just a little extra moisture can be enough to help with snow formation. Overcast skies showed the amount of low-level moisture prevalent across the area at the time. On this particular morning, the air coming from Big River Electric Coleman Power Station’s smokestacks near Tell City, IN provided enough extra moisture to help form a snow plume that stretched from Perry County, through Floyd County, and into the Louisville Metro thanks to winds out of the southwest. While only flurries flew in WAVE Country that day. Several inches to nearly a foot of snow have fallen in other scenarios.

On January 17, 2018, just outside of Cincinnati in Boone County saw a dusting of snow thanks to the Miami Fort Power station in Ohio releasing steam into the cold air. An inversion, an increase of temperature with height, kept the moisture from rising causing ice crystals to grow and snow to fall.

On December 9, 2015, a sewer plant helped create snowfall! Yes, a sewer plant! The National Weather Service in State College, Pennsylvania said that as widespread dense fog developed during the early morning hours, temperatures fell into the mid-20s. Moisture added to the atmosphere by “natural condensation process of the local sewer treatment plant,” returned to the earth as light snow. Only a three-square-mile area was affected!

It’s not just power plants that can enhance snowfall in an area, planes can also make an impact.

On November 29, 2018, radar showed a ring of enhanced snowfall stretching from near Chicago O’Hare International Airport out over Lake Michigan. Reports show that temperatures were in the low 20s at the time with dewpoints in the upper teens. With high relative humidity at the time and subfreezing temperatures, it’s likely that the clouds were filled with supercooled water droplets. Airplanes on their final descent into O’Hare passed through this saturated layer most likely releasing tiny aerosols which acted as condensation nuclei for snowflakes or the lift around the wing of the aircraft caused ice crystals to form which in turn were condensation nuclei.

A 2012 study by the U.S. National Center for Atmospheric Research found that aircraft can increase the number of ice crystals that form in a cloud as they passed through clouds; they called this process “inadvertent seeding.” Their study found that the ice crystals were “produced through spontaneous freezing of cloud droplets in air cooled as it flows around aircraft propeller tips or over jet aircraft wings.” They also found that the “growth of the ice particles can induce vertical motions with a duration of 1 hour or more, a process that expands the holes and canals in clouds.” Overall, researchers said that while worldwide impacts are minuscule, areas near airports can see additional precipitation.

That same effect seen near O’Hare has been observed near Louisville International Airport.

On the morning of January 10 during WAVE 3 News Sunrise, Meteorologist Brian Goode and I noticed a snow shower being enhanced just to the south of the Louisville airport; winds were coming from the north that morning. As UPS airline traffic heading north began to increase around 4:30 AM, the shower continued to grow. Once airline traffic ceased around 6 AM, so did the snow shower. A light dusting was reported on nearby roadways due to the area of enhanced snow. While the exact cause of the enhanced snow shower in that area would have to be studied more, the increased airplane traffic at that time of the day certainly seemed to have an impact. UPS’s meteorologists also noticed the phenomenon on the 10th.

“On rare occasions, aircraft operations can create small, localized bands of snowfall. It’s important to understand this is an infrequent situation, and most of the time only results in a few snow flurries,” UPS said in a statement. “UPS’s meteorologists are aware of the specific conditions necessary for the snow bands to form and have noted it from time to time, including Jan. 10. This is not a new phenomenon – the same thing takes place downwind from the smokestacks of power plants.”