Undoubtedly humans are influencing the world’s climate. But we can also have an impact at smaller scale and shorter time frames – in other words, on the weather.
In the USA, on December 3rd and 4th unseasonably cold air settled over the Plains and the Midwest but there wasn’t a lot of snow with it – except in a few very specific locations, one of which was spotted in Allen County, Indiana, by our forecasting office in Indianapolis. The Northern Indiana National Weather Service also saw it and issued a series of rather unusual Special Weather Statements for “industrial plant induced snow”.
So what was happening? There is a steel production plant near Fort Wayne, and like all such factories it generates a lot of exhaust heat and moisture as well as minuscule particulates. While ordinarily this steam simply evaporates, under favorably cold conditions it can serve to seed a layer of air that’s already replete with ice crystals and supercooled water droplets and cause snowflakes to form and fall.
One of the statements coming out of the NWS office noted that one of the northern Indiana snow bands was intense enough to lower visibility to half a mile (0.8 km) along Highway 30 between Fort Wayne and Columbia City, while near Arcola an observer reported 1.5 inches of accumulated snow (nearly 4 cm). The radar image around 4 pm shows the development clearly.
Indiana was not alone. Cleveland, Ohio, is no stranger to this phenomenon either. It often sees lake-effect snow which is created by a similar process involving additional moisture and warmth but from Lake Erie rather than any unnatural source. On Tuesday this was enhanced by industrial steam across the metro area, and it is so familiar to the NWS office in Ohio that they dub it “Cleveland effect snow”. On Monday December 3rd a coal plant near St Marys, Kansas, was also busily producing industrial-effect snow downwind, with some of settling on the city of Topeka, while parts of Minnesota and eastern Nebraska saw similar flurries and even some freezing drizzle. This radar image shows a well-defined snow line developing southwards of factories near Norfolk, Nebraska, and passing across populated areas like Columbus and Highway 80 west of Lincoln.
This radar view depicts hydrometeor classification rather than just precipitation type – pink implies ice crystals and pale blue is dry snow. Up to two inches (5 cm) of snow was reported downwind.
High resolution models are getting better and better at picking up on small scale weather but usually geographically induced rather than anthropogenic. There is a way to go before they can represent such hyper-local effects – as yet it remains uncertain as to why some industrial plants seem more capable of producing snow than others. These are features that through research and post-processing we are becoming more capable of capturing. And what is increasingly certain, however, is the local and short-term effects humans are inflicting on themselves, whether it be the corn belts inducing higher rainfall, paved areas increasing run-off and raising flooding risks, or sudden snow showers bringing hazards to our roads – ironically, sometimes due to the factories producing the materials for the cars in which we travel them.
Senior Meteorologist / Energy Meteorologist