ATLANTA (AP) — A winter storm that dumped 4 inches of snow in parts of Mississippi was hitting Alabama on Thursday afternoon, with the system expected to spread across northern Georgia and into the Washington, D.C., area, according to the National Weather Service.

The winter blitz follows days of heavy rain across much of the Southeast.

In Huntsville, Ala., a mix of thick snowflakes and sleet fell, turning roadsides and plowed farm fields white.

Traffic slowed to a crawl on the bridge spanning the Tennessee River, with snow accumulating on guardrails. The river was swollen out of its banks after days of heavy rain across north Alabama. Some areas of the state had received as much as 6 inches of rain since Sunday.

Officials closed NASA's Marshall Space Flight Center in Huntsville because of the threat of slippery roads. Engineers postponed an outdoor rocket test to give workers time to get home.

In Mississippi, winter storm warnings had expired and the snow was expected to melt by early afternoon. The last time central Mississippi got at least 2 inches of snow was in February of 2010.

Winter storm warnings remained in effect for parts of Alabama, Georgia, North Carolina and Tennessee.

In northern Georgia, the heaviest snow was expected to fall in the mountains, with lighter amounts possible in parts of the Atlanta area. Schools in at least five counties in the northwest part of the state dismissed early Thursday. Winter weather advisories were in effect across at least 25 counties, set to expire between midnight and 7 a.m.

Snow also was possible across much of North Carolina, with as much as 9 inches in the northwestern mountains. Snow was expected as far east as Elizabeth City.

About 1 to 3 inches of snow was expected in the Washington area and parts of central Maryland. In Washington, a winter storm watch was replaced with a less-serious winter weather advisory. Federal offices were open Thursday.

A winter weather advisory also was issued in South Carolina, with up to 3 inches of snow expected in the northern part of the state.

In Virginia, the National Weather Service expected snowfall to range from a dusting in Hampton Roads to as much as 9 inches in the Blue Ridge Mountains and other high elevations.

The moisture may be welcomed by farmers in the Southeast, notably in those states hardest hit by the nation's worst drought in decades.

An update Thursday by the U.S. Drought Monitor showed that about 59 percent of the continental U.S. remains gripped by some form of drought. More than 91 percent of Georgia is in drought, as is about a third of Mississippi.

Climatologists and hydrologists have called winter precipitation — and lots of it — crucial in breaking the grip of drought and restoring moisture to soil and pastureland.