The second-to-last installment in the annual Screen on the Green series is tonight. They’ll be showing “The Thin Man” near the Washington Monument at around 8:30 or 9 p.m. tonight. With partly cloudy skys and lows around 70, it sounds like a great night for an outdoor film. Here’s what HBO says about the film:”Based on a Dashiell Hammett novel, it’s a picture of sophistication-on-screen, where urbane husband/wife sleuths somehow found time to solve murder…