NEW YORK—A fresh wave of wintry weather will keep a vast swath of the United States in a deep chill over Valentine’s Day weekend, forecasters said on Friday, an outlook that should encourage pandemic-weary Americans to stay home and snuggle up around a fireplace. Snow and freezing rain could fall from Seattle to Washington, and from North Dakota to Louisiana, said meteorologist Marc Chenard at the National Weather Service’s Weather Prediction Center in College Park, Maryland. “Lots of winter weather. This is about as busy as you‘ll get for weather across the country,” Chenard said on Friday. Bitter cold was already gripping the Plains on Friday, just a day after winter weather battered the United States from coast to coast, including freezing rain as far south as Fort Worth, Texas, where six people died in a multi-vehicle pileup. Temperatures as low as minus 45 degrees Fahrenheit gripped Montana and Minnesota …