The new storm caught sightseers on the highways after dark, looking at damage from earlier storms.
Local television radar screens clearly showed the tell-tale "hook" signature of a tornado as it advanced across the local terrain, relayed nationwide by CNN.
Tornado spotters followed the twister as it remained on the ground as broadcasters warned residents to take cover immediately.
The new storm system covered central Oklahoma, centered on the northern suburbs of the city. The previous storms had hit southeastern sections of the city.
Earlier Gov. Brad Henry toured the already tornado-damaged areas of south Oklahoma City Friday and said the areas are devastated.
Henry declared a disaster emergency in Oklahoma and Cleveland counties. He also said the state insurance commissioner estimates damage at more than $100 million.
At least 100 people were injured and more than 300 homes were destroyed when a tornado ripped through several Oklahoma City suburbs late Thursday.
"It is amazing to me that we didn't loose lives," Henry told reporters Friday. "We are so thankful there were no fatalities."
He described the damage as "very significant," and promised that the devastated areas would "as we have done in the past, rebuild."
The governor also said that area postal carriers would collect any food left on front porches on Saturday. The food will go directly to those in need from Thursday's severe storm.
Oklahoma City was expected to receive a second night of rough weather Friday.
Meanwhile, an unusual live broadcast on the National Weather Service radio network more than two hours before the twister struck about 5:10 p.m. is being credited with saving lives during the rush-hour twister.
"For the first time ever we went live on the weather radio at 2:30 in the afternoon and we outlined the situation: the map features, the dry line, the potential for very significant storms and tornadoes, and what time we expected it," said Rick Smith, warning coordination meteorologist for the NWS Forecast Office in Norman, Okla.
The live broadcast was a first for the office, which uses 10 transmitters to broadcast weather information on a 24-hour basis to battery-powered radios in homes, cars, and storm shelters across 48 counties in Oklahoma and eight in North Texas.
"All the response we have received from people has been incredible," Smith told United Press International.
The actual tornado warning was issued 20 minutes before the twister hit Moore, a suburb south of Oklahoma City, which again gave the public an early warning about the approaching twister.
As the tornado moved through the area, the weather service gave "blow-by-blow" coverage on the weather radio network, Smith said. There were hours of notices on the network during the day about the unstable weather.
The same weather situation was setting up for late Friday.
At the National Oceanic and Atmospheric Administration's Storm Prediction Center, which issues all the severe storm forecasts for the nation, Warning Coordination Meteorologist Dan McCarthy said the highest risk for tornadoes Friday was in western and central Oklahoma and south central Kansas.
Since last Sunday there have been 248 tornadoes reported across the nation, and McCarthy said forecasters don't see a break until this coming Sunday. It might be a short respite, however, as more unstable weather is expected in the middle of next week.
"Other than super outbreak in 1974 where we had 148 tornadoes in 16 hours this will be talked about because we've had 248 tornadoes over five days," he said from his office in Norman. "It seems to be quite a stretch of days for tornadoes. Usually we have two or three days and it quiets down for about a week. This is probably one of the most prolific stretches we have had."
This week's twisters have killed at least 40 people in Missouri, Kansas and Tennessee.
Tornadoes also menaced Missouri and Kansas again Thursday. One twister ripped the roof from an apartment building and damaged the houses in southwest Lawrence, Kan., but there were no injuries reported. Oklahoma was the hardest hit area.
"The devastation that's been left behind from more than 200 tornadoes this week alone is shocking," said Terry J. Sicilia, executive vice president of Disaster Services for the American Red Cross.
Red Cross spokeswoman Nancy Retherford told United Press International Friday the non-profit organization was in desperate need of donations to assist the victims of the disaster.
"The Red Cross has $5 million in disaster funds left," Retherford said. She said the Red Cross needs funds to meet the immediate needs of people affected by the tornadoes and storms.
Retherford said people who want to contribute could do so at redcross.org.
Moore, south of Oklahoma City, was the target of a major tornado for the second time in four years, but this one was not deadly like the one in 1999. An F-5 tornado, the strongest possible on the Fujita scale, nearly flattened Moore, killing 38 people. Early reports were that Thursday's tornado was a large F-2 or small F-3.
More than 300 homes were destroyed and another 1,500 were damaged by the latest twister, which also struck a General Motors truck plant and swept by Tinker Air Force Base, although there was no damage reported at the base. Another 34 homes suffered major damage in nearby Choctaw.
Thursday's tornado followed nearly the same path of the deadly 1999 twister across Oklahoma City's southern suburbs moving in a northeasterly direction. It crossed four interstate highways, turning over cars and even a bus. Most of the injuries were to people who were caught in their cars.
Crews were working to restore power to 37,000 residents in south Oklahoma City, Moore and Choctaw. Red Cross volunteers were on the scene to aid the homeless and crews working to clear the debris in the hard-hit area for the second time in four years.