Severe thunderstorms, flood threat to track across Midwest into Friday night

By Brandon Buckingham, AccuWeather Meteorologist

Updated Sep. 27, 2019 2:49 PM

The nation's heartland will face the risk for severe thunderstorms into Friday night. Areas from Rockford, Illinois, to Topeka, Kansas, may have to deal with damaging thunderstorms.

A combination of moisture sources from the Gulf of Mexico and the Pacific Ocean will lead to plenty of available moisture for thunderstorms across the region.

Southerly winds and unseasonably warm air feeding into this area will provide continuous fuel throughout the day. This atmospheric setup will allow for multiple rounds of showers and thunderstorms to track over the same areas throughout the day and into the night.

An approaching cold front will act as a triggering mechanism for another round of thunderstorms late in the day and into the overnight hours. It will be along the cold front that strong to severe thunderstorms will erupt.

These storms could track over some of the same areas that experienced rain earlier in the day. With rainfall rates of 1-2 inches per hour possible, flash flooding may become an issue.

As mentioned, these thunderstorms will be able to tap into the hot and unstable air that will be feeding in from the lower Mississippi River Valley. This will be combined with a favorable upper air jet stream pattern, providing large-scale support for ascent within the atmosphere over the area.

This will provide the necessary ingredients to brew up thunderstorms capable of producing large hail, flash flooding and damaging wind gusts capable of reaching an AccuWeather Local StormMax® of 70 mph.

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These thunderstorms will form in response to a clash between two very different air masses coming together. A very cold air mass dropping southward from Canada into the northwestern United States will clash with the hot air mass in place over the southern U.S. The zone where these masses meet generally results in unsettled weather.

This atmospheric setup becomes common during autumn as cold air from Canada begins to intrude into the U.S. more frequently. Often times the Midwest, Ohio River Valley and the lower Mississippi River Valley can find themselves in the zone where severe weather is possible.

In the wake of the storms Friday and Friday night across the Midwest, a piece of the departing system is expected to lag behind across portions of Iowa, Missouri, and Kansas.

Heavy, gusty and locally severe thunderstorms may erupt from parts of the southern Plains to the eastern Great Lakes region on Saturday.

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