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Much of north Georgia, including metro Atlanta, remains under a tornado watch through early Sunday morning, the National Weather Service said Saturday afternoon. The weather system that is passing through northern Alabama into Georgia was continuing to create concerns, said NWS forecaster Laura Griffith.

"The storm has put us at moderate risk for severe weather," which is slightly higher than NWS expectations for dangerous weather on Friday, she said.

The NWS said earlier Saturday that it expected the worst damage to occur in Atlanta/Fulton County and has sent some search-and-rescue teams there.

Some tornado warning sirens sounded in areas north of Atlanta Saturday. The sirens always go off when there is a tornado warning, officials said. There are 74 sirens around the various counties, with an additional 16 in Smyrna.

Meanwhile, NWS storm surveyors are inspecting the damage in downtown Atlanta to determine whether last night's severe weather was actually a tornado. The surveyors collect damage reports from witnesses, police and emergency officials, businesses, and a helicopter fly-over of the area to make a determination.

Once weather specialists say if it was a tornado, they'll work to rate the twister based on the damage. A similar process determined that recent severe weather in the Memphis area was the result of a tornado.

"We're not exactly sure how this compares to other storms (in metro Atlanta)," Griffith said.

The last tornado to strike close to downtown hit the governor's mansion in the Buckhead area, she said.