WASHINGTON - The D.C. region will warm up overnight, but that's just a respite from what's to come.
What one meteorologist calls a "polar vortex" - a counter-clockwise rotating pool, of cold, dense air - will grip much of the nation as the week begins, including the greater Washington area. The cold snap beginning Monday night could bring temperatures that haven't been seen in decades.
On top of that, the entire WTOP listening area is under a Dense Fog Advisory until 6 a.m. Monday. People who are driving on highways and interstates in the area should take extra and extreme caution.
As far as the cold, ABC7's Ron Riley says we'll get the worst of it on Monday night and Tuesday: Low temperatures will dip into the single digits, with wind- chill factors heading below zero. And Tuesday will be "the coldest day in almost 20 years," with highs only reaching the teens, he says.
The National Weather Service agrees, saying that temperatures in Fairfax County will go down to 2 degrees, with highs on Tuesday reaching 13, and 15 in Arlington County.
It's the same story in Maryland, as the NWS predicts highs of only 14 in Prince George's County and 13 in Montgomery County. Even in the District, where temperatures are generally a bit warmer, the weather service predicts it'll get down to 5 degrees on Monday night, with a wind-chill factor of 8 below, and Tuesday highs of 15.
The temperature in Winchester could drop to minus-4 degrees Monday night, according to the NWS, while Dale City could see a low of 2 degrees.
In the meantime, the north and western suburbs will see the freezing rain continue. An ice storm warning has been issued for Loudoun, Frederick, Washington and Jefferson counties until midnight Sunday. Carroll County, Md., also has an ice storm warning that ends at 9 p.m. Sunday.
Southern moisture will continue to move north and could create travel difficult especially on secondary roads along the Interstate 70 and 81 corridors, says ABC7 meteorologist Chad Merrill.
Temperatures will inch up overnight as that warmer, southern air moves in. However it will create foggy conditions, Merrill says.
Start to the work week forecast
Temps will grow colder during the morning commute as rain showers turn into snow showers, which could cause slippery road conditions, according to Merrill.
"Temperatures will rapidly drop from near 50 degrees, it will be very warm, down to the 30s," he says.
By Monday night, it will be dangerously cold as lows in the District reach zero to 10 above, which will feel like -5 degrees with the wind chill.
The deep freeze elsewhere
In Southwest Virginia, 3 to 5 inches of snow are expected in Tazewell and Bland counties. Temperatures could fall to zero to minus 10 degrees by Tuesday morning. Wind chills may reach minus 10 to minus 30 degrees.
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Single-digit temperatures are expected in other parts of Virginia by Tuesday morning. Wind chills may reach zero to minus-10 degrees.
The cold is hitting the entire country hard - parts of New England already dropped below zero on Saturday, and the outlook for Sunday's playoff game between the Packers and 49ers in Green Bay, Wis., calls for 2 degrees at the time of the late-afternoon kickoff.
In Minnesota, schools are already closed on Monday for the entire state - the first time that's happened in 17 years.
Looking to get away to the South? That'll help some, but even Miami will only hit 61 on Tuesday.
The Associated Press contributed to this report. Follow @WTOP on Twitter.
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