Residents of Oklahoma, Nebraska, and Kansas are braced for a major tornado outbreak, which has been predicted to strike this weekend -- with its peak on Saturday -- according to the National Weather Service's Storm Prediction Center.

A small twister has already touched down in Oklahoma City on Saturday, Reuters said, while noting no injuries have been reported so far. However, one home has major roof damage, while trees, power lines, and fences have been knocked down by heavy winds, Oklahoma City representative Kristy Yager told the news agency.

On Friday, a tornado struck close to the University of Oklahoma campus in Norman around 4 p.m. CDT. The twister ripped the roofs off several buildings, downed power lines, and uprooted trees in Norman, which has 110,000 residents and is located just 20 miles south of Oklahoma City. Norman's city hall was also damaged.

Sirens blared across much of Oklahoma City early Saturday, where three possible tornadoes were being tracked. Residents in the region braced for a day of what forecasters are calling life-threatening storms. The most intense of the storms are expected to hit Saturday afternoon and possibly continue through the night into Sunday, according to CBS News.

Severe thunderstorms -- as well as tornadoes -- are expected to strike throughout the Midwest, according to the National Weather Service, which described atmospheric conditions as constituting a potentially dangerous situation. It said severe storms are possible in Texas, Iowa, South Dakota, and Minnesota.

The storm environment appears to be very favorable for supercell thunderstorms capable of producing very large hail and damaging tornadoes for long paths from late afternoon until at least midnight, said a National Weather Service advisory quoted by Reuters. Fast-moving tornadoes continuing after dark will heighten the risk to life and property.

Large cities on alert include Omaha and Lincoln in Nebraska; Topeka and Wichita in Kansas; and Oklahoma City and Tulsa in Oklahoma.

Especially with it being a weekend, we really want to make sure that the public is aware that this is a serious threat and make sure that people are prepared, Keli Cain, a representative of the Oklahoma Department of Emergency Management, told Reuters.