Heavy rains prompted officials to issue a flash flood emergency in north-central Colorado until 4 a.m. MT (6 a.m. ET). Flood watches and warnings were also issued across patches of Wyoming, Kansas, Nebraska and Missouri.
Weather Channel lead forecaster Michael Palmer told NBC News there had been some reports of hail the size of grapefruit. And residents in the town of Simla, Colorado, about 60 miles southeast of Denver, posted pictures of large balls of ice to their Twitter accounts.
Several rivers and creeks in Kansas City flooded as a result of persistent, heavy rain from Wednesday and Thursday. At least 17 river gauges across the city were at flood levels as of 3 p.m. local time Thursday, The Kansas City Star reported.
In other parts of the Missouri, the ground was so saturated that “as little as one inch of rain could lead to flash flooding in some areas,” the NWS warned.
The severe weather was expected to calm down through Friday morning, Palmer said, before picking back up in Colorado for another round in the afternoon.
On Saturday, Nebraska, Iowa, South Dakota and Minnesota were set to get their share of severe storms, he added, before the system moved further east on Sunday, when it was expected to hit Great Lakes and Ohio Valley.
Alexander Smith is a senior reporter for NBC News Digital based in London.
Jacob Rascon is an NBC correspondent based in Dallas. He reports for all NBC News platforms including NBC Nightly News with Brian Williams, the Today Show and NBCNews.com.
Rascon joined NBC from KNBC in Los Angeles in the summer of 2014. Since that time, he has led the network's coverage of the largest wildfire in Washington state history, the crash of Virgin Galactic's SpaceShipTwo over the Mojave desert and deadly tornadoes in Mississippi. He reported from Havana immediately following the announcement that the United States would resume diplomatic relations with Cuba after fifty years.
At KNBC, he helped lead the station's coverage of devastating California wildfires, mudslides and floods, the LAX shooting rampage, the manhunt for ex-LAPD fugitive Christopher Dorner and the Huntington Beach riots.
Prior to KNBC, Rascon worked at KFOX in El Paso, helping lead the station's coverage of devastating Texas wildfires, floods and ice storms, and illegal immigration, cartel violence and border politics.
Prior to KFOX, Rascon worked with ABC News in the Middle East during the Arab Spring, standing among more than one million Egyptians as they demanded the resignation of Hosni Mubarak, then Egypt's president.
He also worked at the Salt Lake Tribune newspaper in Salt Lake City, Utah and KBYI radio in Rexburg, Idaho, and even and reported out of Haiti after the 2010 earthquake.
Rascon lives in Dallas, Texas, with his wife and three children.