* Front contract slides 4.2 pct this week on mild weather * Near-term cold in Midwest and East limits downside By Joe Silha NEW YORK, Feb 1 (Reuters) - Front U.S. natural gas futures ended lower on Friday in a seesaw session, pressured by a mild outlook for later next week that should slow heating demand despite strong gas use this week as cold weather settled into the Northeast and Midwest. "People are going back and forth about the weather. The market was up early on the cold