A storm that dropped several inches of wet, heavy snow overnight knocked out power to tens of thousands of homes and businesses in the Triangle on Thursday and closed schools and other institutions yet again.

As road crews worked to clear the slushy snow from streets and roads, officials warned that black ice will likely form Friday morning, posing a new round of road worries. The National Weather Service has issued an winter weather advisory for black ice from 9 p.m. Thursday through 10 a.m. Friday.

Schools in Orange, Durham and Franklin counties and Chapel Hill-Carrboro are closed Friday, and N.C. State University and UNC-Chapel Hill have canceled early morning classes. Johnston County schools will open two hours late.

Wake County has opened an emergency shelter at Sanderson High School on Dixon Drive in North Raleigh for people without power. Johnston County will open a shelter at 6 p.m. at the First Baptist Church Ministry Center on South Fourth Street in Smithfield. And Orange County will open a shelter at Smith Middle School on Seawell School Road in Chapel Hill at 7 p.m.

Forecasters had been predicting the storm for several days, and its arrival overnight helped minimize traffic problems. Gov. Pat McCrory noted that there had been no deaths or serious injuries reported as a result of the storm and called that “very, very good news.”

What wasn’t expected, though, were the widespread power outages as snow and ice weighed on powerlines and tree branches.

“We had more power problems than we anticipated due to the curve balls of the weather pattern,” McCrory told a midday briefing at the state Emergency Operations Center, which he said was operating on generators because its commercial power supply was out.

Power outages were widespread across the region, but especially heavy in Raleigh, Durham and Chapel Hill. At their peak, the outages affected about 150,000 Duke Energy customers in the Triangle.

Statewide, power outages peaked at about 230,000 customers at around 9 a.m., and had dropped to less than 180,000 by noon, most in the Triangle area, according to state officials. As of about 1:30 p.m., North Carolina’s electric cooperatives were working to restore power to approximately 16,000 customers.

The storm dumped between 4 and 7 inches of snow in most Triangle communities. The National Weather Service’s unofficial snowfall totals as of 7 a.m. included as much as 6.1 inches in parts of Wake County, 7 inches in Durham and Orange counties and 9 inches near Graham, in Alamance County.

The slushy snow melted some Thursday, as temperatures inched above freezing. In Knightdale, town spokesman Brian Bowman said crews were wrapping up their plowing operation about 1:30 p.m.

“The roads are in pretty good shape,” Bowman said. “It’s pretty slushy, which made clearing easier. They made really good progress.”

But with temperatures expected to dip into the mid-20s overnight, wet roads are expected to turn icy again Friday morning.

“Roadways will freeze and black ice will form” overnight, said Col. William J. Grey, the State Highway Patrol commander. He urged drivers not to be overconfident Friday when road surfaces look clear.

“A lot of accidents occur after the storm has left,” McCrory said.

Raleigh police warned that the power outages meant a lot of intersections were without traffic lights, and they urged drivers to be cautious there.

Between about 8:30 p.m. Wednesday and 8 a.m. Thursday, Raleigh officers handled 72 calls to help motorists and 40 accident calls, police said. A week earlier, without a storm, the comparable numbers were 7 assists and 15 crashes.

The National Guard said it had about 80 members in 40 vehicles helping to patrol roads, including checking on stuck drivers or abandoned vehicles.

On U.S. 64 eastbound in Wake County, a Guard spokesman said, a civilian car hit a Guard Humvee parked on the shoulder Thursday morning. None of the guardsmen were in the vehicle, and the other driver received minor injuries and did not want to be taken to a hospital, the spokesman said.

School was canceled in Wake, Durham, Franklin, Orange, Chatham and Johnston counties as well as in Chapel Hill-Carrboro. The state Office of Emergency Management said 82 school districts in the state were closed.

Duke, N.C. Central, UNC-Chapel Hill and N.C. State universities canceled Thursday classes.

At Raleigh-Durham International Airport, the website Flightaware.com showed 102 cancellations and two delays. RDU showed some late-morning and most afternoon flights on schedule.

State Department of Transportation crews sprayed brine on the highways Wednesday in advance of the storm, to reduce the amount of snow that would stick to the pavement.

Brining before the storm used 1.6 million gallons, Transportation Secretary Tony Tata said. Crews who worked all night plowing also used 11,000 tons of salt and 1,700 tons of sand-salt mixture, he said.

McCrory noted the costs of supplies for storm-fighting and said he also needs to get data about reduced state tax income from businesses being closed in the storm.

The governor also remarked on two years of unusually hard February weather that he said the state is not used to.

“If I could issue an executive order (for better weather), I’d do so, but apparently that doesn’t apply to Mother Nature,” McCrory quipped at the end of his briefing.

Staff writer Kara Bettis contributed.