Storm headed to eastern half of US, threatening major snowfall in DC and flooding in the South

PHOTO: Nevada is among the states to see significant snowfall this week.PlayABC News
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A major storm is headed to the eastern half of the country, bringing snow, ice and rain from the Plains to the Northeast to the Southeast.

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Over 280 flights were already canceled for Wednesday as the storm takes shape.

Here is the latest forecast:

One storm gained strength Tuesday morning, spreading heavy rain across the South.

Meanwhile, a separate storm is bringing snow to Arizona, New Mexico, Colorado and the central Plains.

The storms will merge Wednesday morning, bringing heavy snow to Minneapolis, Chicago and Washington, D.C.

PHOTO: Tracking the storm ABC News
Tracking the storm

The nation's capital is forecast to see 4 to 6 inches of snow before the storm changes to ice and rain Wednesday afternoon. Areas west of D.C. could see 12 inches of snow.

A wintry mix of snow and ice will move into New York City and Philadelphia Wednesday afternoon, bringing 1 to 3 inches of snow.

Philadelphia schools will be closed Wednesday as the storm moves in.

PHOTO: Tracking the storm ABC News
Tracking the storm

In the Midwest, Minneapolis is forecast to see 5 to 8 inches of snow while Des Moines could get 6 to 9.

Chicago is forecast to get up to 2 inches.

Meanwhile, in the South, very heavy rain will continue, with a potential for flash flooding through Wednesday night.

PHOTO: Rainfall Forecast ABC News
Rainfall Forecast

ABC News' Christine Theodorou contributed to this report.