The Storm Prediction Center is warning that a large section of the central U.S. is at risk for "potentially strong tornadoes" on Sunday, adding to what has already been an active March for tornadoes.Over 25 million Americans fac e an enhanced risk of severe weather on Sunday, with the middle Mississippi Valley and lower Ohio Valley being under the highest risk. Cities facing an enhanced risk of severe weather include Memphis, St. Louis, Nashville, Indianapolis, and Cincinnati.An additional 80 million Americans have at least a marginal possibility of encountering severe weather on Sunday.RELATED STORY | Can you guess which country has the dirtiest air?However, there remains a bit of uncertainty regarding how widespread the severe weather will be, as morning storms could diminish some of the energy for more potent afternoon storms.Storm Prediction Center meteorologist Steve Goss wrote that Sunday's "developing storms would pose substantial, all-hazards severe risk including very large hail, strong/damaging winds, and potentially strong tornadoes" within the threatened areas.As new forecast models emerge, Goss said the Storm Prediction Center may increase the severe weather threat across the region.Storms are expected to develop in the Central Plains on Saturday. The Storm Prediction Center said tornadoes aren't expected to be large or violent, but there could be a few touchdowns in a region spanning from Oklahoma City to north of Kansas City.RELATED STORY | Earth breaks yearly heat record and pushes past a dangerous warming thresholdThe storm system could also cause severe weather on Monday along the East Coast, with potentially strong storms expected to affect areas from New York to Florida.This storm system comes at the end of what has been the most active March for tornadoes in at least three decades. The National Weather Service has recorded 236 tornadoes so far this month.Most of the tornadoes, an estimated 167 touchdowns, occurred during a two-day span on March 14 and 15. So far this month, Mississippi has experienced 53 tornadoes, the most of any state. Missouri has had 36, while Illinois has had 33. All three states could add to their tornado totals based on the Storm Prediction Center's forecast. ...read more read less