* Front month remains well under recent 21-month high * Weather forecasts mainly mild for the next two weeks * Nuclear power plant outages back above normal * Coming Up: EIA natgas storage data on Thursday By Eileen Houlihan NEW YORK, May 28 (Reuters) - U.S. natural gas futures slid about 2 percent early on Tuesday, extending Friday's losses after the long Memorial Day holiday weekend. Traders said fairly mild weather expected for the next two weeks and expectations for another above-average inventory injection were weighing on prices despite the return of weekday industrial demand following the holiday. As of 9:15 a.m. EDT (1315 GMT), front-month June natural gas futures on the New York Mercantile Exchange were at $4.153 per million British thermal units, down 8.4 cents, or just under 2 percent. The nearby contract expires on Wednesday. The front month hit a one-month low of $3.883 on May 9 after climbing to a 21-month high of $4.444 on May 1. The latest National Weather Service six- to 10-day forecast and the eight- to 14-day outlook, both issued on Monday, called for above-normal temperatures for most of the nation. But traders said much of the above-normal readings may not be hot enough to spark heavy air conditioning demand yet. Nuclear plant outages totaled 14,700 megawatts, or 15 percent of U.S. capacity, down from 16,500 MW out a year ago, but up from a five-year average outage rate of 13,900 MW. Early injection estimates for Thursday's gas storage report from the U.S. Energy Information Administration range from 80 billion cubic feet to 103 bcf versus a 72-bcf build during the same week last year and a five-year average rise for that week of 92 bcf.