National Weather Service United States Department of Commerce

Thunderstorms and Heavy Rains Across Portions of the Central and Eastern US; Heat Expands to Portions of the East

Widespread showers and thunderstorms, some severe, may produce heavy downpours and flash flooding across much of the eastern and central U.S. Dangerous heat will continue in the Pacific Northwest and expand across portions of the East. Deep tropical moisture and associated thunderstorms will bring heavy rainfall and localized flash flooding across portions of Florida into the central Gulf Coast. Read More >

Overview

On the afternoon of July 17th, 2018, thunderstorms developed over the Black Hills. Some of these storms became severe, producing large hail and damaging winds. However, the main issue with these storms was a significant amount of small hail, covering the roads and making travel difficult. Snow plows were needed to clear inches of hail from the roads. Additionally, heavy rain caused flash flooding, which was exacerbated by hail-covered roads. The storms over the Black Hills eventually moved southeast onto the plains. More thunderstorms moved into northeastern Wyoming, becoming severe and producing large hail and strong winds. Heavy rain with these storms also produced flash flooding. These storms merged to form one storm system (what meteorologists call a mesoscale convective system, or MCS), and spread into South Dakota. 

 

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