The combination of mild, moist air and long nights will create the perfect conditions for fog to form during the last weekend of 2019.
Motorists and airline passengers hoping to get an early start and beat some of the traffic may have a wrench thrown into their plans by Mother Nature, even during a seemingly benign weather pattern this weekend.
Fog will vary across the countryside and metro areas in the central and eastern United States, and will be most prevalent after midnight through the midmorning daylight hours.
Even though the fog may favor valley locations and proximity to inland streams and rivers, it can form miles away from these waterways.
An added danger this time of the year has to do with the temperature.
Even though there is moisture in the air and the days will bring above-average temperatures, the long nights can allow the air to cool to below freezing. Where moisture produced by the fog collects on the ground, or on elevated surfaces, such as bridges and overpasses, a thin layer of ice can form. This black ice can appear to be wet.
During Saturday morning, locally dense fog was reported in nearly two-dozen states east of the Rockies. Freezing fog was reported in parts of southeastern Pennsylvania, New Jersey, Kansas, Nebraska, Colorado and New Mexico.
Motorists traveling on the highways will need to be extra vigilant as the visibility can vary from a half a mile to near zero over short distances. By traveling from the late morning to the early evening hours, motorists may avoid most of the fog-related issues.
Freezing fog contributed to a multiple-vehicle pile up on Interstate 64 in southeastern Virginia during the weekend before Christmas.
During Friday morning, Dec. 27, 2019, a fog-related multi-vehicle crash on Highway 84 near Lubbock, Texas, severely injured a state trooper.
Fog can also be a major problem at the airports and lead to substantial delays and even flight cancellations in some cases. This can occur when the fog is so dense that pilots cannot see the runway. In some cases where fog is affecting a destination, flights may be held at the departure airports until the fog has eased.
Fog can take much longer to burn off during the winter, when compared to the early autumn due to the low sun angle. Usually during the winter, dry air is around when there are no storms bringing precipitation. But, while there is a major winter storm affecting the Central states this weekend, clear and calm conditions amidst the mild, moist air have allowed fog to form from parts of the Mississippi Valley to the Atlantic coast on Saturday.
On Sunday, the area that may experience late-night and morning fog will be generally limited to the eastern third of the nation and along parts of the central Gulf coast, prior to the arrival of drier and cooler air.
Fog can also form in the deeper valleys of the West where some moisture can gather, even though the surrounding air is generally dry.
Download the free AccuWeather app to check the forecast in your area and receive fog-related advisories. Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.