Thanksgiving is forecast to be colder and with more snow than usual across large swathes of the U.S., threatening to snarl what the AAA is projecting to be record holiday traffic.
The big picture: The National Weather Service warns the "polar vortex," an area of cold air around the Arctic, could expand southwards and combine with two other factors to bring "cooler than normal temperatures" from Seattle to Dallas and across to Chicago this Thanksgiving week.
- "Below normal temperatures are favored for the Central and Northern U.S., including northern parts of the Pacific Northwest, the Great Plains, parts of Texas, and the interior Mid-Atlantic," the NWS said in posts to its social media accounts.
Driving the news: Another contributor to the forecast extreme weather event is the Madden-Julian Oscillation, an eastward-moving "pulse" of clouds, rainfall, winds and pressure, per the NWS.
- These two factors plus La Niña are set to "drive winter-like conditions across much of the U.S. late November into early December," according to the weather agency.
Threat level: The frigid temperatures are set to coincide with peak holiday travel this week — as nearly 82 million Americans are expected to embark on Thanksgiving holiday road trips and the TSA prepares to screen an estimated 17.8 million air travelers from this Tuesday.
- The TSA expects to screen over 3 million on Sunday alone.
- The NWS says the extreme weather may start as early as Tuesday, "with spatial coverage and confidence increasing during the Nov 26-30 period."
Zoom in: There's a "moderate risk of heavy snow for the Central Rockies" from Nov. 29-Dec. 1 and for the Upper Great Lakes and the Interior Northeast Nov. 29-30, "driven by the potential for lake-effect snow," per the NWS' Climate Prediction Center.
- "Broader slight risks cover much of the Rockies (Nov 29-Dec 5), and the Northern Tier corridor from the North Central U.S. to northern New England (Nov 29-Dec 2)," the Climate Prediction Center says.
- Cooler temperatures may persist into at least mid-December over the northern tier.
Between the lines: Multiple studies suggest polar vortex excursions may be becoming more likely as the world warms, but this remains an area of active research.
- "Disruption of the Stratospheric polar vortex is a natural process, it happens almost every or every few winters," Tampa Bay meteorologist Jeff Berardelli notes on X.
- Scientists are "investigating how climate change/Arctic Amplification etc… factors in and IF it is making them more common."
Go deeper: How Arctic warming may have blasted US with the polar vortex
