NEW YORK — Snow from a widespread winter storm began falling Saturday over most of the Northeast and the upper Ohio River Valley, the second in less than a week for the regions.

The National Weather Service expected up to a foot of snow in parts of southern New England, with the heaviest snowfall possibly in Providence, R.I., and Boston, which declared parking bans to allow snow-removal vehicles to clean the streets. Winterstorm warnings were in effect in parts of those states and in Connecticut.

New York City and Philadelphia saw a mix of rain and snow as the storm moved in from the west. In Ohio, Dayton, Columbus and Cincinnati saw 2 to 5 inches of snow by Saturday afternoon, the National Weather Service said.

“Expect those accumulations to kind of work their way northeastward through much of New York state and much of New England,” said meteorologist Brian Hurley of the National Weather Service.

About 20 vehicles piled up in a storm-related chain-reaction crash on Interstate 93 in New Hampton, N.H., police said, and five people were injured.

Drivers throughout the regions were warned to be cautious. Officials lowered the speed limit to 45 mph on much of the Pennsylvania Turnpike, about 300 miles from the Ohio state line to east-central Pennsylvania.

Flights at Philadelphia’s airport were delayed about an hour, mostly arrivals, spokesman Stacy Jackson said.

Parts of southern Indiana saw 6-8 inches from the storm, some in areas that had received more than a foot from a blizzard last week.

Front Section, Pages 2 on 12/30/2012