Hours after one or more lethal tornadoes smashed into Armour, in Columbus County, meteorologists were carefully watching intense, spinning storms pass farther north, hoping they remained aloft.

To their relief, they did.

"It could have been much worse," said Jeff Orrock, warning coordination meteorologist for the National Weather Service in Raleigh.

Spring is North Carolina's busiest tornado season. But a second peak strikes in November, when meteorological conditions can also be favorable to twisters.

Thursday's storm started assembling in Texas on Tuesday and moved east, producing tornadoes in Louisiana, Mississippi, Alabama, Florida and South Carolina on its way here, the weather service says.

The collision of cold air from the north and warmer air from the south set the stage for the large storm system. So did unstable, moving air above the ground. Moisture provided from the Gulf of Mexico and Atlantic Ocean fueled heavy rains.

By midnight Wednesday, the weather service knew conditions were right for tornadoes to form. The storm prediction center issued a tornado watch, but a watch is imprecise and can span as much as 25,000 square miles.

Predicting exactly where or when a tornado will strike is not easy, said Robert Digiorgi, lead forecaster with the weather service in Wilmington. Unlike hurricanes that lumber across the ocean for days, tornadoes arise quickly. They happen when a rotating column of air spins fast enough to stretch longer and reach the ground.

The Wilmington office of the weather service issued a severe thunderstorm watch in Columbus County at 6:21 a.m. But a tornado warning isn't issued until a twister is actually seen or is expected. Radar picked up spinning, and the weather service issued a tornado warning. That was at 6:29 a.m.

The ground strike is believed to have begun eight minutes later, at at 6:37 a.m.

That gave no one much warning, especially people still asleep at that time.