* Late-week outlook turns colder for Texas and the Midwest * Cool weather drives front month to 21-month high * Coming Up: EIA, Enerdata natural gas storage data Thursday By Joe Silha NEW YORK, May 1 (Reuters) - U.S. natural gas futures ended lower on Wednesday for a second straight day, pressured by a late wave of profit-taking after colder weather forecasts drove the front-month contract to a 21-month high early in the session. Temperatures in the Midwest and Texas were expected to sink far below normal later this week and generate heating demand. An unexpectedly chilly spring has helped slow storage injections early in the stock building season and left inventories well below normal for this time of year. "The market bumped up early as technical buyers responded to temporary weather-based demand, but we saw some profit-taking late in the session on concerns about the sustainability of the (recent) rally," Gelber & Associates analyst Aaron Calder said. Calder noted that government data on Tuesday showed gross gas production climbed in February, which could mean the market will remain comfortably supplied, even during a warm summer. Front-month June gas futures on the New York Mercantile Exchange ended down 1.7 cents at $4.326 per million British thermal units after climbing early to a 21-month high of $4.444. The front contract lost nearly 6 percent last week, its first weekly decline in 10 weeks, but still managed a 7.9 percent gain in April for the third straight monthly rise. Despite the early run up, technical traders said the market seemed to be struggling, noting prices have broken above the $4.40 level several times in the last two weeks only to be turned back by strong selling or profit-taking. Some said Wednesday's action could signal a downside reversal, noting the front month hit a new high then closed on a weak note. Traders also noted that gas prices at current levels are likely to slow demand by prompting more utilities to use coal rather than gas for power generation and to increase supply by encouraging producers to turn on more wells. ANOTHER LIGHT INVENTORY BUILD EXPECTED Utilities typically stockpile natural gas from April through October, then withdraw stored supplies from November through March to help meet peak winter heating demand. The stock-building season got off to a slow start, with only two injections reported so far after an unusually cold spring forced homeowners and businesses to use more gas for heating. Traders and analysts polled by Reuters are looking for another light storage build when the U.S. Energy Information Administration releases weekly inventory data on Thursday, with most expecting a gain of 28 billion cubic feet. Stocks rose 31 bcf during the same week last year, while the five-year average build for that week is 67 bcf. EIA data last week showed that total U.S. gas inventories had climbed to 1.734 trillion cubic feet, about 807 bcf, or 32 percent, below last year's record highs at this time, and 94 bcf, or 5 percent, below the five-year average. PRODUCTION CLIMBS DESPITE FEWER RIGS The EIA reported on Tuesday that gross natural gas production in February climbed for the first time in three months. Output rose to about 1.27 bcf per day, or 1.8 percent, above the same month last year after dropping below year-ago levels in January for the first time since 2010. The report dimmed prospects that record high output would slow anytime soon despite the fact that the Baker Hughes gas drilling rig count has dropped to a 14-year low. The EIA recently estimated that marketed gas output in 2013 will hit a record high for the third straight year.