[NEW YORK] A widening snowstorm with an encore of freezing rain iced over the US Midwest on Tuesday and headed east, causing hundreds of flight cancellations and closing schools, and was expected to tangle New York and Boston's evening rush hour.

As much as 30cm of snow was predicted for inland parts of New England, as well as up to 10cm in New York City and up to 13cm in Boston before turning to freezing rain in the late afternoon, said meteorologist Dan Petersen with the National Weather Service in College Park, Maryland.

"The big cities along the coast are going to have a pretty quick changeover from snow to sleet and freezing rain and eventually rain," Mr Petersen said in a phone interview. "The danger of snow changing to freezing rain is people slip and slide quite a bit and that's the cause of accidents when people lose control of their cars."

The storm by early morning had iced over Illinois and Michigan and was moving through Wisconsin into northern Pennsylvania and southwestern New York state. The widening storm was expected to reach as far south as northern Delaware and Maryland, Mr Petersen said.

More than 1,600 flights into and out of the United States were cancelled on Tuesday, most of them at airports in Chicago, New York and Boston, according to FlightAware.com.

Ahead of the storm, New Jersey Governor Phil Murphy declared a state of emergency, and hundreds of schools were closed for the day.

REUTERS