A sprawling storm system triggered multiple reports of destructive tornadoes in Ohio, Kentucky and Indiana on Thursday evening.

The big picture: Logan County, Ohio, officials declared a mass casualty event after a suspected tornado hit a trailer park some 70 miles from Columbus, as the storm system unleashed "large damaging hail, wind gusts and a few tornadoes" from far northeast Texas to the Ohio Valley overnight, per the National Weather Service.

In Indiana, state police initially told local media that a suspected tornado at a Randolph County trailer park killed three people, but said at a briefing just after midnight Friday that officials were still working to confirm whether there had been any fatalities as they searched for anyone trapped inside buildings.

• "There have been many, many significant injuries, but I don't know the number. ... I don't know what those injuries are," Indiana State Police Superintendent Douglas Carter said at the briefing about the incident in Winchester. "There's a lot that we don't know yet."

In Kentucky, Gov. Andy Beshear said in a post to X that a tornado that swept through Gallatin, Trimble, and possibly Carroll, counties caused minor injuries earlier on Thursday.

• No fatalities were reported, but there was "significant structural damage," he added.

By the numbers: Over 13 million people in the U.S. were under tornado watches from Texas to Ohio on Thursday night, according to the NWS.

• More than 38,000 customers were without power in Ohio on Friday morning, per PowerOutage.us.
• Nearly 19,000 others in Kentucky and almost 18,000 more in Colorado were also without electricity, according to the utility tracker.

⚠️VERY DANGEROUS HALF MILE WIDE TORNADO on the Ground FROM HURON Emergency Management... damage to homes and structures being report. THIS IS A VERY SERIOUS and dangerous tornado on the ground!!!⚠️ pic.twitter.com/eZp8aOn3uZ

— NWS Cleveland (@NWSCLE) March 15, 2024

Between the lines: The severe weather is the result of a deep dip, or trough, in the jet stream over the Southwest and Rockies, with warm, moist air flowing northward into the Ohio Valley.

• That same trough is helping to deliver a prolonged and crippling snowstorm across parts of the Rockies, including the Denver metro area, with some locations surpassing 45 inches of snow since Wednesday.

State of play: "Heavy snow will continue across portions of the central Rockies and extend into the southern Rockies overnight," per an NWS Thursday night update.

• "A second round of heavy snow will develop over the Four Corners region tonight, continuing into the weekend."

Go deeper... Denver snow totals: Where the winter storm has hit the hardest

Editor's note: This article has been updated with new details throughout.