2 of 7 | Heavy snow falls as a person walks along U.S. Route 42 in Florence, Ky., Monday, Jan. 6, 2025. (AP Photo/Carolyn Kaster, File) 3 of 7 | Workers clear steps at the Capitol in Washington, Monday, Jan. 6, 2025. (AP Photo/J. Scott Applewhite, File) 4 of 7 | Tom Fleischman shovels snow in Cincinnati before dawn on Monday, Jan. 6, 2025. (AP Photo/Carolyn Kaster, File) 5 of 7 | A person holds an umbrella as they walk during a winter storm, Monday, Jan. 6, 2025, in Cincinnati. (AP Photo/Joshua A. Bickel, File) 6 of 7 | A person clears snow from front stairs of a home following a winter storm Monday, Jan. 6, 2025, in St. Louis. (AP Photo/Jeff Roberson, File) 7 of 7 | Cosimos Cendo, of Washington, D.C., skis down Main Street in Annapolis, Md., Monday, Jan. 6, 2025, during a snow storm. (AP Photo/Susan Walsh, File) Frigid air that normally stays trapped in the Arctic has escaped, plunging deep into the United States for an extended visit that is expected to provoke teeth-chattering but not be record-shattering. It’s a cold air outbreak that some experts say is happening more frequently, and paradoxically, because of a warming world . Such cold air blasts have become known as the polar vortex. It’s a long-established weather term that’s become mainstream as its technical meaning changed a bit on the way. What it really means to average Americans in areas where the cold air comes: brrrrr. What’s happening is the jet stream — that usually west-to-east river of air way above ground that moves weather systems along — has made a roller-coaster like dip from the Pacific Northwest to the Southeast and is stuck on that wavy track. To the west of that plunge, in California, it’s […]