Dense fog advisory issued for DC area

BETHESDA, Md. (FOX 5 DC) - Commuters should be cautious on the roads Thursday night as the National Weather Service has issued a dense fog advisory for the D.C. region. 

The agency says that the visibility level in D.C., parts of central, northern and western Maryland is one quarter mile or less. Several areas in Virginia are also blanketed in thick fog, which makes driving conditions hazardous. 

Nearly 100 million people awoke to dense fog on Thursday morning – almost a third of the U.S. population - thanks to a weather pattern that swept warmer temperatures across the nation's midsection in the wake of last week's deadly arctic blast. 

Fog alerts stretched over 1,500 miles across 20 states from Missouri to New York and from North Dakota to as far south as Texas. Some Freezing Fog Advisories were in place for parts of the Texas and Oklahoma panhandle and northeast New Mexico. 

One sign of all this warm air flooding northward, especially if you live east of the Rockies, you've seen it: the fog," said FOX Weather Meteorologist Amy Freeze. "Central and eastern U.S. cities right now socked in with heavy fog as the warm air is overriding the cool air right to the surface."

Thursday set a record for the third-consecutive day for most National Weather Service office "zone" regions under Dense Fog alerts at 1,517, according to Daryl Herzmann, with Iowa State University’s IEM.  Wednesday held the previous record at 1,341. Before the current stretch, the record had been 926 set just over a year ago.

Contributing to the fog is the warmup happening for 270 million Americans this week. This mild weather pattern is interacting with frigid ground leftover from last week’s deadly arctic outbreak.

After nearly two weeks of subfreezing temperatures, it has taken the ground a while to warm back up. 

Vehicles are navigating through thick fog in Toronto, Ontario, Canada, on December 23, 2023. (Photo by Creative Touch Imaging Ltd./NurPhoto via Getty Images)

Meanwhile, with a very moist air mass in place on top of that cold ground, dense fog is forming. 

"That fog is acting as a blanket," said FOX Weather Meteorologist Stephen Morgan. "Any sort of heating that we get throughout the day - not so much from the sun, but just from the mixing of the atmosphere. Because that warmth is spread through the mid-levels, and then it mixes down at the surface."

The dense fog advisory is in effect for the D.C. region until 1 a.m. Friday.

FOX Weather contributed to this report.