Lake-effect snow falling in the Great Lakes region was forecast to be more than 2 feet deep in some areas, forecasters said. Several inches an hour could accumulate Tuesday in areas from Lake Erie and Lake Ontario south into the Appalachians, Weather.com reported. Additional snowfall may reach 6 inches in a few locations across the West Virginia Blue Ridge Mountains, northwest Pennsylvania, southwest New York and central upstate New York. Affected parts of the Great Lakes region were forecast to include Illinois, Indiana, Michigan, New York, Ohio and Pennsylvania, as well as the Canadian province of Ontario. Lake-effect snow comes when cold northwest winds blow over the warmer Great Lakes waters, picking up water vapor that freezes and falls as snow. Southern Ontario was forecast to experience severe weather, with snow-squall warnings for as much as 16 inches of snow. Toronto, which had warmer-than-usual temperatures for the holidays, issued an extreme cold weather alert expecting a high of 12 degrees Fahrenheit Tuesday. Weather.com said 1 to 2 feet of snow could fall on areas northeast of Cleveland to south of Buffalo and east of Lake Ontario. Icy roads led to accidents as snow showers hit Chicago and Dayton, Ohio. The U.S. National Weather Service said as much as 20 inches of snow could fall downwind of Lake Ontario in New York\'s Southern Tier, west of the Catskill Mountains along the northern border of Pennsylvania. More than a foot was forecast to fall in the Rochester, N.Y., area. Buffalo, N.Y., known for lake-effect snow caused by cold wind blowing over an unfrozen Lake Erie, was forecast to be spared Tuesday, with just an inch or two. Northeast of the city, 3 to 5 inches may fall in areas of persistent snow bands, The Buffalo News reported. Windy conditions were forecast to remain in the Middle Atlantic region, with gusts from 25 mph to 40 mph. High temperatures Tuesday were forecast to be 10 to 20 degrees below normal, with temperatures ranging from the single digits and teens across upstate New York and northern New England to near 40 in southeast Virginia, Weather.com said.