Coming off a predicted 40 percent chance of rain Tuesday night in Grass Valley, today is expected to be cooler than the warm first few days of the week, as a cold front moves into the area, said National Oceanic Atmospheric Administration Rorecaster George Cline. "That is going to be the biggest effect of the cold front is the temperatures dropping off," Cline said. "Your best chance of showers will be Wednesday."Expect partly cloudy skies with a high in around 50 degrees, Cline said. Thursday won't much different, he said, with clouds hovering over Grass Valley through Friday.However, warmer temperatures …