Arctic blast, tied to the polar vortex, spreads all the way to Southeast
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An invasion of frigid air from the Arctic is sweeping south from the Plains and Ohio Valley Sunday, moving towards the Southeast and East.
Threat level: The colder-than-average temperatures threatens public health for those exposed to the wind and cold, and may harm water and power infrastructure from North Dakota to Texas, on eastward.
- The extreme cold has links to the polar vortex, which is a feature of the winter climate during winter in the Northern Hemisphere.
- "Life-threatening" wind chills down to minus-55°F are likely in the Plains and Upper Midwest, the NWS warns, mentioning the risk of hypothermia and frostbite for people exposed to the cold for too long.
- Sub-zero wind chills are forecast to affect the Ohio and Tennessee Valley Sunday night through midweek, with the possibility of similar cold spreading into portions of the Mid-Atlantic and Northeast in the wake of a winter storm.
Along with the cold, a snowstorm is affecting areas from the Mid-Atlantic to the Northeast on Sunday into Monday. It is poised to potentially become the heaviest snowstorm so far this year for Philadelphia, New York City and Boston, with 5 to 10 inches possible in this broad region.
What they're saying: "This will be the coldest air of the winter season thus far, and in many cases the coldest in several years," the NWS warns.
Zoom in: The hazardous cold will be especially disruptive in the South and Southeast, where temperature departures from average will be significant and persistent.
- A rare winter storm is set to deliver a severe snow and ice storm from Houston to Baton Rouge and New Orleans, eastward towards the Carolinas beginning Monday.
- As of Sunday morning, the National Weather Service was calling for about 3 inches of snow to fall in Houston, with up to 5 inches in parts of the metro area.
- About 2 to 3 inches of snow are expected to fall in New Orleans, with 4 to 6 inches in Baton Rouge.
The intrigue: The NWS forecast office in New Orleans is urging residents to "Exercise extreme caution if travel cannot be avoided" due to the cold and snow that is expected.
- "Given the rare southerly track of this winter storm, major traffic and travel disruptions are likely through mid-week," the NWS stated in an online forecast discussion.
By the numbers: Here's how some cities will be affected early next week:
- Minneapolis: A high of minus-5°F with a low of minus-13°F on Jan. 22.
- Denver: A high of 6°F and a low of minus-4°F on Jan. 20.
- Dallas: A high of 33°F and a low of 23°F on Jan. 21.
- New York City: A high of 18°F and a low of 10°F on Jan. 21.
- Washington, D.C.: A high of 21°F and a low of 11°F on Jan. 21.
Meanwhile... The Arctic outbreak will result in a blustery and frigid Inauguration Day, with temperatures in the upper teens and wind chills even lower on the National Mall when President-elect Trump takes the oath of office inside the Capitol to protect attendees from the cold.
The intrigue: The cold air may also spill westward into the Great Basin, setting up yet another period of strong, offshore Santa Ana winds in Southern California.
- The Storm Prediction Center has issued a rare, "extremely critical" wildfire risk outlook for Monday across some of the same areas hit by the devastating wildfires earlier this month.
Zoom out: The factors behind this cold outbreak include a strong high pressure area or "ridge" in the jet stream across the eastern Pacific north to Alaska. Meanwhile, there's a dip, or "trough," in the jet stream across central portions of the U.S.
- This is allowing Arctic air to surge southward.
- Also, in the upper atmosphere, the polar vortex is currently becoming "stretched" from north to south across the North Pole.
- It is expanding southward and helping to promote the flow of air from northern Canada southward toward the continental U.S., said Judah Cohen, a meteorologist at Atmospheric & Environmental Research.
Zoom out: The polar vortex in the stratosphere is altering the jet stream one atmospheric layer down, in the troposphere. This is where most weather takes place.
- This interaction between the polar vortex and the jet stream may be favoring the strong area of high pressure over Alaska and downstream trough, according to Amy Butler, a researcher at NOAA, and Simon Lee of the University of St. Andrews.
- Both researchers said this interaction is likely to be more short-lived than what happened during the infamous polar vortex winter of 2013-2014.
Over longer timescales, studies suggest polar vortex shifts may be more likely due to human-caused climate change, but this is an area of active research.
