More summer-like warmth in central U.S., though storms loom CHICAGO (Reuters) - Forecasters predicted another day of unseasonably warm weather east of the Rocky Mountains on Sunday as one of the mildest winters on record entered its final week. But the National Weather Service and others warned a powerful cold front in the West slowly creeping east could trigger severe storms and tornadoes in the evening from Nebraska to Texas and bring heavy rains and possible flooding in the coming days as it lingers over Texas, Louisiana and Arkansas. That late winter storm kept temperatures well below normal in California on Sunday and generated heavy snow fall in several states, including Arizona, where several highways in the northern part of the state were temporarily closed, according to the Arizona Department of Transportation. With the official start of spring still a few days away, the National Weather Service said temperatures would be 25 to 30 degrees above normal on Sunday in Michigan, Indiana, Illinois, Wisconsin, Missouri and South Dakota. Cooler and more seasonal weather was expected to return to country's midsection in the second half of the week, along with rain, but forecasters said temperatures were likely to remain above normal. Things are eventually going to cool down. The question is exactly when," said Frank Strait, a meteorologist with AccuWeather.com. It's starting to look as though that storm that is over the western states now will take a little longer to push eastward than we originally thought. So it may take a little longer to get the cool down in place in the Midwest. The National Storm Prediction Center warned of a risk of severe weather on Sunday in parts of Nebraska, Kansas, Oklahoma and Texas with the possibility of dangerous thunderstorms known as supercells. Roger Edwards, a meteorologist at the Storm Prediction Center, said the primary risk was for large hail and damaging straight line winds. But he said the storms could trigger "a few tornadoes" as well. Two weeks ago last Friday, a chain of fast-moving twisters spawned by massive thunderstorms killed dozens of people in the Midwest and South. In the West, a winter storm was expected to bring another day of rain to the coast and snow further inland on Sunday. In California, the rain was heavy in places and snow levels dropped low enough in the mountains to force the closure of some passes, AccuWeather.com said. In Arizona, heavy snow in the area around Flagstaff temporarily closed portions of several interstate highways, according to the transportation department. "It's a pretty large and sprawling system," Strait said. I've seen reports of over two feet of snow in the Sierra and I'm sure we'll hear similar reports from the Colorado Rockies, the Wasatch in Utah and areas in northern Arizona. Additional reporting by David Bailey; Editing by Paul Thomasch