Winter storm to wreak havoc on Northeast travel

— -- A major winter storm is bearing down on the Northeast and promises to shut down transportation throughout the region on Tuesday.

Washington, D.C., will be the first city hit by the snowstorm, and residents can expect 4 to 6 inches, forecasters say.

Philadelphia could see nearly 10 inches, while New York and Boston will likely get at least a foot.

Thousands of flights have been canceled at airports from Washington, D.C., to Boston as airlines scramble to prepare. Here's what you need to know:

Air travel is coming to a halt

American Airlines, United Airlines and Southwest Airlines announced Monday that all Tuesday flight operations in and out of New York City airports have been canceled.

Additionally, American Airlines has shut down operations in Philadelphia for most of Tuesday and in Washington, D.C., before 8 a.m., and in Boston after 8 a.m.

United Airlines is canceling all Boston flights after 9 a.m. on Tuesday and is expected to cancel Washington, D.C., Baltimore and Philadelphia operations later Monday night and into Tuesday morning.

Southwest Airlines canceled 1,333 flights in response to the winter storm, including many of those in and out Baltimore, Boston, Washington, D.C., New York and Philadelphia.

Airlines will move aircraft that would have otherwise spent the night in New York City tonight to other nearby hubs. This will allow them to not only avoid any damage but also to resume full operations sooner.

American Airlines, Delta Air Lines, United Airlines, Southwest Airlines and JetBlue have all issued travel waivers to passengers affected by the storm. They will be able to rebook on another flight without fees.

FlightAware shows nearly 4,000 flights already canceled for Tuesday.

Roadways will be dangerous

Forecasters are expecting 10 to 14 inches of snow Tuesday with wind gusts of up to 50 mph, making roadways unsafe for driving.

New York City Mayor Bill de Blasio announced that public schools have been canceled for Tuesday.

"This would certainly be the biggest snowstorm of the 2017 winter season in New York City," Faye Barthold, a weather service meteorologist based on Long Island, told The Associated Press.

Pennsylvania Gov. Tom Wolf lowered speed limits on some interstates in eastern Pennsylvania, which takes effect on Monday night. Certain large vehicles have also been banned from those roadways until Tuesday evening.

Modified Amtrak service between D.C. and Boston on Tuesday

While the Northeast Regional train will operate on a modified schedule Tuesday to deal with the winter storm, Amtrak has canceled Tuesday's Acela service between New York City and Boston.

Amtrak also announced Monday that other long-distance trains in the Northeast will be affected by the storm. Train service has been suspended between Albany/Rensselaer and Boston, and between Pittsburgh and Washington, D.C.

ABC News' Whitney Lloyd contributed to this report.