A powerful winter storm was sweeping east from the Plains on Sunday, driven by what meteorologists describe as an intense cyclone, setting off a chain reaction of snow, ice, rain, and severe weather expected to affect much of the country.

Heavy snow and strengthening winds spread across the Upper Midwest, where the National Weather Service warned of whiteout and blizzard conditions that could render travel impossible in some areas. Snowfall totals are expected to exceed a foot across parts of the upper Great Lakes, reaching up to 2 feet along the south shore of Lake Superior.

In the South, meteorologists warned of severe thunderstorms signaling the arrival of a sharp cold front, which could bring a sudden temperature drop and strong north winds, ending days of record warmth in the region.

Over the next 48 hours, the cyclone is poised to produce heavy snow and blizzard conditions in the Midwest and Great Lakes, freezing rain in New England, thunderstorms across the eastern U.S., and widespread strong winds.

The storm is expected to intensify as it moves east, drawing energy from an intense clash between frigid air descending from Canada and warm air lingering across the southern United States, according to the National Weather Service.

This storm follows thousands of flight delays and cancellations across the Northeast and Great Lakes earlier this weekend due to snow, as travelers faced disruptions during the busy holiday travel period between Christmas and New Year’s.

Meanwhile, on the West Coast, California experienced a dry weekend after earlier powerful storms caused heavy rains, flash flooding, and mudslides, resulting in at least four fatalities.