(Updates with detail from Wisconsin)
Dec 20 (Reuters) - Holiday travelers heading home for Christmas may face some rough going this weekend as a winter storm threatens tornadoes, floods, snow and ice for a wide swath of the United States.
Forecasters are predicting up to a foot (30 cm) of snow for some parts of the Midwest, while other states slightly to the east already have flood watches in effect. Snow had already begun in parts of Idaho and Oregon by late afternoon on Friday, and was expected to continue on Saturday.
Some 94.5 million people in the United States are expected to be on the roads traveling at least 50 miles (80 km) from Dec. 21 to Jan. 1, according to the AAA, an automotive group.
One of them, Emily Williams, a 25-year-old graduate student at Notre Dame University near South Bend, Indiana, will be driving more than 12 hours through the soaking rains and severe storms expected on Saturday to her family's home in Ocean Springs, Mississippi.
"It's going to be raining or foggy for my whole drive, so I am worried about slick roads, visibility and - of course - other drivers," said Williams.
In Wisconsin, icy morning roads and freezing rain led Dan and Rosemary O'Brien to put off by several hours their planned departure for a 150-mile trip to visit relatives in Racine.
"You could hit a bad patch in the road and then you're bad," said Dan O'Brien, 70, at a Wendy's restaurant south of Milwaukee where the couple had taken a break Friday afternoon.
In addition to the icy Midwest woes, tornadoes are threatened along the central Gulf Coast on Saturday night, according to the National Weather Service, which is also predicting heavy snow for northern New England.
Williams hopes to be home before the tornadoes hit.
On Saturday, rain and thunderstorms are expected to begin an onslaught from the Texas panhandle through the Ohio Valley, with damaging winds and flooding likely in some areas, according to the National Weather Service.
Severe weather with potential tornado activity threatens the Southern Plains states of Louisiana, Arkansas and Mississippi, according to the Weather Channel.
Further south along the East Coast, where temperatures could reach record highs of 60 to 70 Fahrenheit (16 to 21 Celsius) over the weekend, travelers would do well to get in most of their road time before a cold front hits the region on Sunday evening, according to Accuweather.com.
Downpours and high winds are then expected to pummel states from Georgia to New York with icy conditions forecast in northern New England, making for poor travel conditions there late Sunday and Monday.
The bad weather is expected to give way to sunny skies and moderate temperatures over most of the United States by Christmas Eve on Tuesday, with some patches of snow and rain but mostly mild conditions, said meteorologist Chris Dolce of the Weather Channel.
"The map really clears out," he said. (Reporting by Emily LeCoz in Jackson, Mississippi; Heide Brandes in Oklahoma City; Karen Brooks in Austin, Texas; Brendan O'Brien in Milwaukee and Sharon Bernstein in Sacramento; Editing by Scott Malone, Leslie Gevirtz and Lisa Shumaker)