Authorities are once again warning of smoky conditions and low visibility on roads for Friday morning.

Weather and smoke conditions are forecast to be favorable for what’s called a “super-fog event,” caused when smoke combines with water vapor, fire officials said. Visibility will be “near zero” Friday morning and could necessitate road closures.

The fire in the Great Dismal Swamp National Wildlife Refuge now has burned about 6,071 acres and has plagued the area with smoke for weeks.

Conditions are expected to be at their worst between 4 and 9 a.m. along U.S. Route 58 and Interstate 664 in eastern Suffolk and western Chesapeake, fire officials said.

Drivers are advised to check traffic reports before their morning commute, give themselves extra time for morning trips and drive with caution.

The Virginia Department of Environmental Quality has issued a “Code Red” air-quality alert for Friday. A Code Red alert means that the air is unhealthy for everyone. The general public, even those who do not typically suffer from respiratory conditions, may experience mild health effects. Sensitive groups, such as children, older adults and those with chronic heart or lung illness, may have more serious health problems.

More than 430 people now are assigned to fight the fire. Downed trees and crumbling roads, both results of the fire’s destruction, are impeding firefighting efforts, according to officials at the swamp.

The firefighters have set up a system of pumps to suck water from Lake Drummond and flood the swamp. The fire is now a slow-moving, smoldering ground fire in peat fuels.

The Suffolk Police Department issued the following precautions for drivers traveling in the smoke:

• Slow down and turn your low-beam headlights on.
• Signal turns well in advance and brake early as you approach a stop. Remember that the vehicle behind you cannot see either.
• Keep your windshield and headlights clean.
• If you need to pull off the roadway, use the nearest exit rather than simply pulling to the side. If no exit is available, pull over as far as possible.
• Make sure everyone in the vehicle is buckled up or secured in a child safety seat.
• Delay your trip if possible.