NEW YORK, May 23 (Reuters) - U.S. natural gas futures traded nearly flat early on Thursday after slipping slightly in the prior session, with volume light as traders stepped back ahead of a weekly inventory report due later in the morning. Traders and analysts polled by Reuters expect to see that domestic gas stocks rose last week by 91 billion cubic feet when the U.S. Energy Inventory builds have exceeded market expectations for three straight weeks as mild May weather slowed overall demand, but traders said warmer forecasts for next week and into early June were likely to slow injections. "Market chatter continues to focus on forecasts for warmer than normal temperatures as a source of ongoing support for prices," Citi Futures energy analyst Tim Evans said in a report. At 9:10 a.m. EDT (1310 GMT), front-month gas futures on the New York Mercantile Exchange were down 0.5 cent at $4.181 per million British thermal units after trading overnight between $4.163 and $4.223. Chart traders said the market seemed stuck in a range, with good support in the $3.90 area and resistance in the $4.20s. But with supplies still comfortable, many traders remain skeptical of the upside, at least until a broader-based heatwave forces more air-conditioning loads. Mostly below-seasonal temperatures are expected for the eastern half of the country for the next five days, but private forecaster Commodity Weather Group said the six- to 10-day outlook had turned hotter again for the central and eastern United States. Despite a steep decline in dry gas drilling over the last year and a half, production has not slowed much, if at all. The EIA still expects output in 2013 to post a record high for a third straight year.