Icy conditions forced the closure of the I-10 twin span bridge between Slidell and New Orleans about 3:30 Tuesday afternoon, State Police confirmed.

The closure was on the New Orleans Police side, said Trooper Greg Marchand. On the north shore, it was shut down at Old Spanish Trail in Slidell.

The closure means both major arteries between the north and south shores, the Causeway and the I-10 bridge, were shut down due to freezing temperatures and the mixture of rain, sleet and snow that fell much of the day Tuesday.

The Causeway was closed about 1:15 Tuesday after an accident near the drawbridge, according to General Manager Carlton Dufrechou.

The bridge remained open through the first few hours of sleet and freezing rain, but ice was forming on the high-rise portions of the bridge, Dufrechou said.

With sleet and freezing rain expected to continue most of the day Tuesday and temperatures not expected to get much above freezing on Wednesday, Dufrechou said he wasn’t sure when the bridge would reopen.

“Our target is to open it as soon as possible,” he said.

By mid afternoon Tuesday, sleet was beginning to accumulate on both sides of St. Tammany Parish, and it continued to fall steadily.

Ken Graham, of the National Weather Service, said though the precipitation would continue, any snow would come at the very end of the storm, likely late Tuesday night or early Wednesday morning.

Temperatures in the clouds above Slidell range as high as 40 degrees, decreasing the chance for snow and increasing the chance for freezing rain, Graham said.

Graham sent up a balloon around 11 a.m. that showed that the clouds between 2,000 and 9,000 feet were warmer than surface temperatures, he said, meaning that snow falling from higher altitudes was melting on its way down before freezing and falling as sleet or hitting the ground and then freezing.

The best chance for snow would be near the end of the rain late Tuesday or early Wednesday, he said.

“We have a long way to go,” Graham said.

With the weather worsening, Northshore Square Mall in Slidell announced it would close at 2 p.m. Tuesday. In a Facebook post, mall officials said the mall would reopen Wednesday. Both Slidell Post Offices were also closing.

The mall was mostly empty an hour before it was set to close, and people who worked there said few shoppers had put in an appearance.

At Forever 21, clerk Joey Green said the last time the mall had closed it was because of a power loss during a storm.

He had been at the store since early morning. “We’re forever open, even when its 21 degrees outside,’’ he joked.

Temperatures are expected to hover around 30 degrees well into Wednesday, Graham said. Sleet and freezing rain began falling on the north shore around 11 a.m., later than some projections.

Earlier Tuesday, before temperatures had hit the freezing mark, the Red Cross had opened a warming shelter in Slidell. Later in the day, three additional shelters were opened in Tangipohoa Parish. They are located at West Side Middle School,401 West Oak Street in Amite; Hammond Junior High School, 111 J.W. Davis Drive in Hammond and Kentwood High School, 601 Ninth Street, Hammond.

The first occupants at the Slidell warming shelter arrived shortly after it opened in John Slidell Park’s gymnasium Tuesday morning. Robert Cuppay of Lacombe and his 90-year-old mother, Emma Cuppay, live in a home heated by propane. But Cuppay said he has to keep their home warm for his elderly mother, and during cold weather the propane can run out quickly. With icy road conditions in the offing — and the fact that fuel is expensive — they played it safe by going to the shelter, just as they did on Friday.

The gym is also closer to Slidell Memorial Hospital, he pointed out.

Red Cross volunteer Lauren Maheu said the agency asks people to bring their own food to the shelters, but the Red Cross does have some heatable meals on hand, as well as coffee.

Last Friday, only about six people came to the warming shelter, Maheu said, and some of them were homeless. As of noon Tuesday, the Slidell shelter had five people.

Many businesses around the parish were open Tuesday morning, and shoppers were still stocking up for the storm. At the Walmart Neighborhood Market on the corner of East Causeway Approach and U.S. 190, lines at 10 a.m. stretched five or six deep at registers.

Shannon McGuire was shopping with his daughter.

“We came last night, and it was a madhouse,” he said, comparing the shopping scene to a hurricane. McGuire said his family planned to stay indoors, make and eat soup and play checkers, he said.

A customer service clerk at the store said the store was busier than a normal Tuesday morning, but that no decisions had been made on whether to close if the weather got worse.

None of the power companies that serve St. Tammany Parish reported major outages. Three Cleco customers lost power but were restored by 4:15 p.m.

All have said that they have extra crews on hand to deal with outages as quickly as possible.

Officials warned residents to stay away from any downed power lines and report them. Those who have generators should not plug them into a home outlet, officials said.

They also urged residents to take all necessary precautions to stay warm and to be careful when using portable heaters.

Phone numbers for electric providers are:

Cleco — 1-800-622-6537

Entergy — 1-800-968-8243

Washington - St. Tammany Electric Cooperative — 1-866-672-9773