A giant swirling mass of air from the North Pole is expected to hit the D.C. area beginning Monday, bringing with it some of the coldest temperatures in two decades.
The “polar vortex” affecting a massive area that stretches from the Plains to the Carolinas could bring temperatures to some areas outside the Beltway that drop to record lows, National Weather Service officials said, and at the very least keep residents bundled up through Wednesday.
“The actual temperature Monday night will be single digits close to 0 in the western suburbs and middle single digits” at Ronald Reagan Washington National Airport, Weather Service meteorologist Bryan Jackson said. “For the D.C. metro area, after sunset we’ll have wind chills below zero. That night we expect wind chills ranging from negative 10 to negative 15.”
The District hasn’t felt sub-zero temperatures since 1996, when a January blizzard dumped more than 2 feet of snow on the area. The region enjoyed relatively mild temperatures Sunday, considering what’s to come in the days ahead, with some areas in Southern Maryland hovering around 50 degrees, Mr. Jackson said.
Rain falling late Sunday was likely to change to snow before ending, but the Weather Service was not expecting much accumulation. Areas far west of the District could get up to 2 inches of snow, but the larger concern was the wind chill warning for the areas west of the Blue Ridge Mountains.
“The cold front comes late [Sunday], from the west,” Mr. Jackson said, “It’s passing up the Appalachians and in the wake of it is a strong cold front with Arctic air behind it. The cold air starts building in Monday morning and it’ll spread across the area.”
Weather officials said Tuesday will be the colder of the two days as the vortex passes over the area. Monday’s high is forecast to be 45 degrees in the morning and then to average in the low 30s until sunset.
“Tuesday itself will be in the high mid-teens,” Weather Service meteorologist Brian Lasorsa said. “Right now we have 14 [degrees] for [Washington Dulles International Airport], 16 for Reagan.”
The record low temperature for Dulles on Jan. 7 is 8 degrees, set in 1988. The current forecast for Dulles is a potentially record-breaking 3 degrees for Tuesday. The current forecast is 7 degrees for the District on Tuesday, and the record low for the District on Jan. 7 was set in 1884, at 5 degrees.
Those lows won’t even begin to near the mercury drop caused by the vortex in other areas of the country.
The vortex, Mr. Lasorsa said, is a circulation of air normally settled above the Arctic region.
“It’s the vortex itself tracking toward the north, with a ton of cold air, basically Arctic air, from Montana down through the Mid-Atlantic and Carolinas,” he said.
The counterclockwise-rotating pool of cold, dense air will affect more than half the continental U.S., with wind-chill warnings stretching from Montana to Alabama.
School has been canceled across the state of Minnesota because of a forecast predicting temperatures as low as 31 degrees below zero. Fargo, N.D., is predicted to have temperatures at 25 below zero, while Illinois and Indiana could reach 15 degrees below zero.
And the cold spell comes as several states in the Midwest are digging out from as much as a foot of recent snowfall.
Some southern states such as Georgia and Alabama were bracing for potentially record low temperatures in the single-digits.
What’s unique about the D.C.-area weather, Mr. Jackson said, is that the more windy of the two days is going to be colder.
“It’s called radiation cooling,” Mr. Lasorsa said. “The heat near the Earth’s surface escapes into the atmosphere. When it’s windy you don’t have that element of radiation.”
While lower temperatures are usually recorded on clear, calm nights, the strong winds on Monday are going to keep the mercury low.
“All Monday night and all Tuesday we’re expecting cold air to be in place and building with strong winds,” Mr. Jackson said, adding that Monday night would bring “very low wind chills.
“The wind factor for Monday compared to Tuesday makes all the difference,” he said.
• This article is based in part on wire service reports