(CNN) -- New Jersey and Delaware look set for a blizzard starting Friday afternoon, and Washington and Baltimore, Maryland, may experience "near-blizzard conditions" starting Friday, the National Weather Service said Thursday.
The blizzard warning for New Jersey and Delaware takes effect Friday at 4 p.m., while the winter storm warning for the nation's capital and surrounding areas starts Friday morning at 10 a.m.
The expected New Jersey blizzard will make travel "extremely dangerous," the agency cautioned. The warning means "severe winter conditions are expected," while snow, strong winds and poor visibility are likely, leading to "whiteout conditions."
The storm could drop up to 24 inches of snow on southern New Jersey and 12 to 18 inches on Delaware and the central New Jersey coast, the National Weather Service in Mount Holly, New Jersey, said.
The blizzard warning remains in effect until Saturday at 7 p.m. It replaces an earlier winter storm watch, which is less severe.
Washington and Baltimore will be under a winter storm warning from 10 a.m. Friday until 10 p.m. Saturday.
The winter storm warning is issued when significant amounts of snow are expected or occurring.
The storm will make travel "very hazardous or nearly impossible Friday night," the agency warned.
Amtrak has canceled most Friday service from Washington southward, it said Thursday. Washington schools will dismiss students at 12 p.m. Friday and cancel all after-school programs, the school system announced Thursday night.
Baltimore, Maryland, Washington and the surrounding north Virginia area could receive 16 to 24 inches of snow, with Philadelphia, Pennsylvania, getting eight to 12 inches.
Winter storm warnings also cover most of Pennsylvania, Virginia, West Virginia, central Indiana, Ohio and western North Carolina.
New York residents could face 4 to 9 inches of snow between Friday and Saturday, the weather service said, but there is a chance the storm system will remain south of the city.
In the Southeast, heavy rain Thursday will cause widespread minor flooding and isolated moderate flooding across the region, forecasters said. Flood watches are in effect for southeastern Louisiana, to east-central Georgia, with western South Carolina and eastern North Carolina also affected.
CNN meteorologist Sean Morris contributed to this report.