Winter conditions are expected to hit the eastern half of the country, from Denver to New York City, as there is a significant change in the weather pattern.
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A major storm is developing in the middle of the country with heavy snow, strong winds and thunderstorms, according to ABC News meteorologists.
More than a dozen states, from the Rocky Mountains to the Northeast, issued warnings or weather warnings for the winter.
The storm system is moving from the Rocky Mountains to the Plains this morning with snow, wind and rain. A series of heavy storms with lightning, strong winds and heavy rains will arrive in Chicago this afternoon, meteorologists said.
A cold front is expected to hit the east coast on Tuesday night, with heavy rain and some thunderstorms.
Several waves of cold air are expected to move through the Midwest and Northeast this week and over the weekend.
The cooler air core will moderate as it moves over the Great Lakes and northeast, but it will still feel like a shock to the system after the last few weeks, forecasters said.
Even the coldest air in Canada will move to the eastern part of the country this weekend, forecasters said.