Saturday morning update: They're playing now, but the weather is threatening. Here's a report from weather.com.FARMINGDALE, N.Y. — Only twice has weather forced an extra day of play at the U.S. Open, but based on Saturday's forecast it looks likely that the 2009 Open will extend into Monday.Players won't complete the first round until Friday afternoon, at which time only half the field will get to begin the second round at 4:30 p.m. The other half of the field won't begin round two until Saturday afternoon.Meanwhile, AccuWeather.com reports more wet weather will most likely drench Bethpage Black on Saturday, most likely leading to another delay of play and possibly another lost day.According to the forecast, "Large thunderstorms have erupted across the Midwest, and that moisture will reach western Long Island Saturday. Periods of heavy rain are possible Saturday afternoon, and there could be another suspension of play."That means the worst of the weather could again fall on the wave of players who tried to play Thursday morning, got rained out and finished round one early Friday."The worst weather Saturday is going to start probably at 2 p.m.," said AccuWeather.com meteorologist Mark Paquette. "It shouldn't be a soaker in the morning. But in the afternoon there could even be some lightning."Sunday's forecast doesn't look much better. A storm off the New Jersey coast is expected to deliver cold, breezy conditions with either sprinkles or light rain."Not as steady as Saturday," Paquette said, "just kind of miserable. Whether or not they can play golf in it just depends on how well the course holds the water."