National Weather Service United States Department of Commerce

Multi-day, Potentially Catastrophic Heavy Rainfall and Severe Weather Event

A multi-day, potentially historic heavy rainfall event may produce catastrophic and life-threatening flooding through Saturday from the Ozarks into the Ohio River Valley. Several clusters of strong to severe storms are expected from the Southern Plains, Mid Mississippi Valley to the Ohio/Tennessee Valleys and the Mid Atlantic. Read More >

Overview

In the afternoon of August 8th, 2020, thunderstorms developed across eastern Wyoming and western South Dakota. These brought large hail and damaging winds to the area through the evening. One storm that developed over the Black Hills produced grapefruit-sized (4.5 inch) hail! As the storms shifted eastward, they formed a line, developing into a mesoscale convective system as more storms converged together. The main threat changed from hail to strong winds, with nearly 80 mph gusts reported across south central South Dakota. As the storms passed, magnificent mammatus was seen by many.  Image
Pactola (R. Strom)
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