A powerful severe storm system moved across the United States on Friday, causing at least three apparent tornadoes from Alabama to Indiana and threatening even more destruction as the day wore on.
National Weather Service meteorologist John Gordon reported Friday afternoon the agency has about "half a dozen reports of tornadoes on the ground," as well as reports of "significant damage" -- stressing all the while that the worst may still be to come.
As of 4 p.m. ET, the weather service had 19 tornado warnings out affecting six states.
"This is an enormous outbreak that's going on right now across Kentucky and the South," Gordon said. "It's crazy. It's just nuts right here."
Two of the reported twisters touched down in northeast Alabama, where residents were assessing damage to a high school, prison and other locales.
And shortly after issuing a tornado watch for large swaths of central and southern Indiana, central and eastern Kentucky and southwest Ohio, the National Weather Service reported that trained weather spotters detected a tornado at approximately 1:43 p.m. CT (2:43 p.m. ET) in southern Indiana.
There was no immediate word on damage or possible casualties from that touchdown in Posey County, near the Ohio River.
In Tennessee, severe weather was responsible for critical injuries of as many as eight people in the cities of Harrison and Oolteweh, officials there said.
The storm brought golf-ball-size hail, strong winds and rain into the two northeast Alabama counties before continuing on a northeastward path into Tennessee.
Between 40 and 50 homes in Hamilton County, Tennessee, have "significant damage that we know about," the county's Chief of Emergency Management Bill Tittle told CNN.
He said that there are 24 reported injuries and, while none of those appear to be life-threatening, he acknowledged that "we have not reached all the homes."
"We obviously have lots of debris, homes with roof damage, streets that are impassable that we have crews cutting down trees with chainsaws in order to get emergency vehicles through, and as of now our crews are just going door-to-door on foot," said Amy Maxwell, Hamilton County, Tennessee, emergency management spokeswoman.
Reporting from that area near Chattanooga, CNN's Rob Marciano observed a continuous stretch of damage about 200 yards wide that ripped what had been brick and mortar homes down to their foundations.
Emergency personnel set up a makeshift triage area at a nearby convenience store for people who were still being pulled out of the rubble on Friday afternoon.
Hamilton County Mayor Jim Coppinger said a touchdown of a tornado had been confirmed, though he expressed optimism that sound preparation and safety measures appeared thus far to prevent any deaths.
"We're just working diligently at this hour to try to make sure that everyone is accounted for," Coppinger told CNN. "And hopefully we'll be able to escape (without fatalities)."
Meanwhile, there were no immediate reports of injuries at either Buckhorn High School in Madison County or the Limestone County Correctional Facility in an adjacent county, both in Alabama.
But there was widespread damage in Madison County, the National Weather Service said, and some injuries were reported, according to a local ambulance service.
The Madison County Emergency Management Agency confirmed that a rain-wrapped tornado was spotted near the Harvest area, just northwest of Huntsville, which itself was hit hard by a tornado last year.
"The key thing that let me know it was serious was the loud wind," said Hovet Dixon of Harvey, Alabama. "It almost seemed like it was trying to lift my roof off."
The scene after the storm passed in the areas where the apparent tornadoes touched down looked similar to what parts of the Midwest and South suffered earlier this week, with damaged homes and downed power lines. Thousands were without power.
The warden for the Limestone Correctional Facility, Dorothy Goode, said the prison was hit by the storm. All prisoners -- the facility holds about 2,200 -- were accounted for, she said.
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These were the first reported twisters from a storm system that threatened the already hard-hit Midwest and South.
Forecasters said the areas most at risk for twisters on Friday were southern Indiana, southern Ohio, most of Kentucky, central Tennessee, northeastern Mississippi and northwestern Alabama.
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Storms were expected to proliferate during the afternoon, with the most likely window for tornadoes between 4 p.m. and 8 p.m. ET, according to CNN meteorologist Sean Morris.
There is the potential for widespread damaging wind gusts, large hail and violent tornadoes in some areas.
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Storms will begin to weaken during the late evening as they move east toward the Appalachians. The severe weather threat will diminish overnight Friday into Saturday morning, Morris said.
These tornadoes follow an earlier outbreak, that began Tuesday night and left 13 dead across Kansas, Missouri, Illinois and Tennessee and battered parts of Kentucky, as well.