CRANSTON, R.I. (AP) — Gov. Lincoln Chafee declared a state of emergency and closed highways to non-essential traffic on Friday, urging residents to take ‘‘extreme caution’’ during a potentially dangerous winter storm expected to dump 2 feet of snow in some locations.

Speaking at a briefing at Emergency Management Agency headquarters in Cranston, the governor and other state officials warned Rhode Islanders to stay off the roads and allow crews to clear them, though snow was expected to fall so heavily at times that they likely wouldn’t be able to keep up. Just before 5 p.m., Chafee closed Interstate 95 and several other major highways to regular traffic.

The National Weather Service issued a blizzard warning for Rhode Island through early Saturday afternoon. Snow began falling Friday morning and was expected to become heaviest overnight. Forecasters predicted wind gusts of up to 60 mph and by Friday night more than 122,000 customers had lost power, with most of the outages in Washington County.

Michael Lewis, director of the state transportation department, said 100 state plows were already out on the roads, bolstered by 200 private contractors.

‘‘The message is to stay off the road and stay safe,’’ he said.

Outages remained the biggest threat from the storm, Chafee said.

‘‘With tree branches laden with heavy, wet snow, the winds picking up and the temperatures plunging all at the same time, it’s a bad combination,’’ he said.

National Grid positioned crews and equipment around the state to respond to outages, according to Timothy Horan, its Rhode Island head. The strongest winds were expected overnight.

Schools across the state were closed Friday even before the first snowflake fell. Public transit service throughout the state was suspended as of noon. T.F. Green Airport canceled all flights for the rest of the day — the last one went out just before 1:30 p.m. — and none was scheduled to leave until Saturday.

Motorists were told to stay off Interstates 95, 195 and 295 and Routes 24 and 146 as night fell and the snowfall picked up. The ban on highway travel did not apply to emergency vehicles, public workers crews, journalists, health care workers or trucks carrying food or fuel. The restrictions were in place until further notice.

Transportation officials said high winds could prompt the closures of the Newport and Mount Hope bridges later Friday and Saturday because of expected high winds.

Downtown Providence was virtually empty of traffic and pedestrians by mid-afternoon. Grocery stores continued to do a brisk business as residents picked up bread, fruit and snacks to have on hand in the event of power outages. Motorists lining up for fuel prompted long lines and shortages at some gas stations.

‘‘I think it’s pretty,’’ said 20-year-old college student Samantha Kush, who ventured out from her Johnson & Wales University dorm room to pick up an essential — diet soda.

She planned to emerge again to make snowmen once the snow stopped.

‘‘We might as well have fun with it, right?’’ she said.

Hospitals and health facilities tested generators before the storm hit to prepare for outages, said Steven Costantino, director of the Health and Human Services department.

Rhode Island’s four-member congressional delegation on Friday wrote to President Barack Obama to ask that federal assistance be made available to Rhode Island, if the state asks for it, to support emergency operations during the storm and recovery after it.

Chafee, who said he encountered long lines himself at the grocery on Thursday as people stocked up on essentials, urged residents to use common sense during the storm.

‘‘Good luck, Rhode Islanders, and take extra caution,’’ he said.

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