Dense fog advisory in effect Thursday into Friday morning

A dense fog advisory has been issued for Long Island from 8 p.m. Thursday through 8 a.m. Friday. That means hazardous driving conditions, with visibility often at a quarter-mile or less, the National Weather Service said.

Earlier advisories have expired for Long Island, but factors such as "very moist air" and an approaching warm front mean that fog is expected to develop overnight, said Joey Picca, weather service meteorologist based in Upton.

Some arrivals at LaGuardia Airport were averaging delays of up to five hours as of midafternoon Thursday, with arrivals into Kennedy experiencing delays of close to an hour, according to the Federal Aviation Administration website. Some departures from those airports, as well as Long Island MacArthur, were affected, and the FAA advised travelers to check with their airlines.

This comes as a warm front moves into the area, bringing drizzle in some spots and causing temperatures to rise to "either side of 60," said David Stark, weather service meteorologist based in Upton.

Reduced visibility could make for hazardous travel conditions, so drivers are advised to "slow down . . . use your low beam headlights . . . and leave plenty of distance ahead of you in case a sudden stop is needed," the service said.

With the fog at some spots "kind of hovering at the ground . . . it's almost like driving through a cloud," Stark said earlier in the day.