NEW YORK (Reuters) - A winter storm bore down on the U.S. East Coast on Wednesday, threatening to snarl New York City’s evening commute after hindering air travel along the East Coast and prompting the shutdown of federal offices in Washington.

Snow turning to sleet slickened roadways in the New York metropolitan area by the early afternoon and was blamed for a rash of fender benders and traffic jams.

The widespread weather system piled as much as 6 inches (15 cm) of snow across the Washington area before turning to sleet, said meteorologist Bryan Jackson of the National Weather Service Weather Prediction Center in College Park, Maryland.

As much as 7 inches of white powder blanketed the south-central Pennsylvania borough of Greencastle.

By evening, the winter storm was set to move into the Boston area, where it is expected to leave just 2 inches overnight before tapering off by the morning commute, forecasters said.

Elsewhere in the United States, a storm system threatened to dump 1 foot (30 cm) to 2 feet of snow in the Four Corners area, near where Arizona, Colorado, New Mexico and Utah come together, Jackson said.

A third system drenched the Southeast with heavy rains that were expected to last through the week, prompting flash flood warnings.

On the East Coast, the storm forced the closing of federal agencies in Washington as well as schools in Philadelphia, Baltimore and the nation’s capital.

Hundreds of flights were delayed or canceled in and out of major airports in Washington, New York, Philadelphia and Chicago, according to Flightaware.com. Airports told passengers on social media to check their airlines for delays and cancellations.