Science behind ‘back door cold fronts’

Published: May. 17, 2023 at 1:05 PM CDT
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QUAD CITIES, Iowa/Ill. (KWQC) - A cold front moved through the TV6 viewing area Tuesday night into Wednesday morning, but it wasn’t your typical cold front. It was what is called a “back door cold front.”

A typical cold front generally moves from north or northwest to south or southeast. It’s usually pushed by an area of high pressure in the western US or Canada.

Cold fronts can bring us rain and storms in the summer, or snow in the winter.

A back door cold front comes from the opposite direction. High pressure moves in from the northeast, and pushes the front from the northeast to the southwest off Lake Michigan, changing the direction of the wind and bringing in cooler temperatures.

The NOAA Glossary defines a back door cold front as a cold front moving south or southwest along the Atlantic seaboard and Great Lakes; these are especially common during the spring months.

Areas along the lake, such as Milwaukee, Wisc. or Chicago, Ill. typically see a bigger influence from these back door cold fronts.

Cool water of the lake influences the back door cold front as it moves onshore, known as a ‘pneumonia front.’ It gets its name because of the fast drop in temperature and was coined by the National Weather Service in Milwaukee back in the 1960s. These fronts typically drop the temperature at least 16° in one hour.

On May 16, the temperature in Chicago went from 81° at 5:30 p.m. to 64° a half hour later.

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