SAN FRANCISCO (MarketWatch) -- Natural-gas futures edged higher Thursday, after the Energy Information Administration reported a 30 billion cubic foot rise in U.S. inventories for the week ended April 19. Analysts polled by Platts forecast an increase of between 27 billion cubic feet and 31 billion. Total stocks now stand at 1.734 trillion cubic feet, down 807 billion cubic feet from the year-ago level and 94 billion cubic feet below the five-year average, the government said. May natural gas     (ngk13)   was at $4.19 per million British thermal units, up 2 cents, or 0.6%. It was trading little changed at $4.17 shortly before the data