140207065415-01-weather-0207-horizontal-galleryA recent stint of warm days and sunshine in the U.S. Midwest and Northeast was just a tease, as forecasters on Wednesday predicted an extended stretch of bitter cold and snow reaching well into March. The wintry conditions were likely to take a firm hold on Thursday in the Midwest and move eastward over the weekend, meteorologists said. “Once again the polar jet stream has plunged southward, tapping bitter cold air directly from the Arctic Ocean. This latest frigid plunge will engulf the nation’s northern tier through the weekend,” wrote The Weather Channel meteorologist Chris Dolce on its website. The arctic air mass was affecting the eastern two-thirds of the nation on Wednesday, with high temperatures some 15 to 30 degrees Fahrenheit below normal in many places, the National Weather Service said. More